Check your radiator/condenser fan operation NOW

[steve6]

I have a 2003 VW Jetta TDI 1.9L. My issue is my a/c isn't blowing cold air, all it's blowing is hot air. I've checked the fuse and its good, then I checked the temp control knob to see if it was sticking in the hot temp setting but after looking at the cable by the gas pedal it was working properly. so then I figured it needs to be recharged with coolant, but when I connect the pressure gauge it reads that there is pressure, but its in the red zone of the gauge. not sure what the issue is but I figure having the pressure being in the red is the reason why my a/c isn't working. what should I do to correct this issue and or what else could be the issue if it isn't the pressure problem?

so I did this step : "Manual AC (as opposed to Climatronic AC or Climatic AC -the transmission type is immaterial) cars, push the AC button in, place a fan in slow and leave your key to ON (engine does not have to be running). Both fans should run in slow (unless it is near freezing or your refrigerant pressure is too low.) If your AC light does not come on and your cabin fan does not work, do not proceed until you have troubleshot and fixed this problem; this is the primary signal to turn on the AC system."

both fans are running. so what is the next step to correct my ac? it still isn't cold at all.

is the a/c clutch kicking in? you can shine a light down to it and see if it is. A common failure is the clutch assembly within the pulley... Test it for resistance, should be 3-6 ohms ish (full spec on the web), but should not be 'open'

 

[Red Dragon]

Just checked mine and the driver side doesn't work. And just as the Georgia summer is kicking off.

 

[Golf2K]

Quote:
Originally Posted by Golf2K View Post
2000 Golf TDI 5spd 411,000 kms

All fuses look fine

Manual A/C, was working last summer, and the A/C compressor was put in a few years ago, and the lines look good. This summer no cold air, A/C clutch doesn't engage.

I did the ignition on test with A/C on, interior fan on and the Rad fans do not turn.

I pulled of the 'Thermo Switch' Plug and jumpered 1-2 got the big fan to turn, small fan did not.

I then jumpered 2-3 on same plug, turned on ignition got nothing, tried all A/C and fan settings, fans did not spin

I hooked a battery up to the Big fan connector and it spun on both settings, the battery was weak so it didn't spin too much faster on the full speed setting, which I think is post 2-3 to a battery.

Small fan did not spin when hooked up the battery, I think I tried every which way.

Sounds like I need a New Fan assembly and possibly a Fan Control Module.

Any tips?
UPDATE:

I replaced the Aux Fan with a new Feb, and a new FCM from Uro Parts, and still nothing. I also got the car up to 93.5c Degrees and the fans did not turn on still.

******************************
New Information, went to a shop, mechanic thinks its the A/C clutch, and is around $400 to fix. ALSO CONNECTED Freon gauge to the connection near the top of the Rad and it looked to have pressure. Did not take any or very little.

New FCM installed, if I jumper the temp sensor plug-in I can get Lo-speed to work, but I cannot get Hi-Speed fan operation to work.

I have un plugged and replugged A/C connections and FCM connections, I tried removing Fuse 16 from cabin and ran car and..... nothing, no rad fan operation, no cold air...

But knowing that the Lo Speed works with the jumper and not the hi speed tells me something. I need to check the power to A/C just need to know how

 

[Golf2K]

UPDATE:

I replaced the Aux Fan with a new Feb, and a new FCM from Uro Parts, and still nothing. I also got the car up to 93.5c Degrees and the fans did not turn on still.

I just test my FCM (both old and new) on a car with working A/C and they both passed the ignition test. Looks like I be getting new wires.

 

[TC282AVIATOR]

Both fans not working with ignition on and blower on low, also AC Clutch not engaging. Found S180 fuse terminal damaged from excessive heat. A quick clean up of the terminal and all is operating normal. THANK YOU !! great advise .

 

[cabot]

I am reconstructing my car after a crash and sitting getting rained in while at the body guy. I am currently on the A/C. I just want to get it where it clicks on properly and starts to take a charge. I have recently realized that it would be good practice to replace my drier and have the system flushed since it was uncharged for several months. I had like nothing working to start. I replaced my FCM and my resistor pack in the cabin fan and continuity tested everything I can think of for voltage and continuity to ground. I have four working fan speeds, an A/C light working properly and properly functioning radiator/condenser fans (I had none of that before). I have a clutch coil that tests at 3.8ohms and engages when I jump battery voltage to it. I have 11.8v and continuity to ground at the connector. The low side is at 90psi. The high side has been holding vacuum for a week. Anyone?

 

[dremd]

So your low side is in Vacuum while high side has 90 psi at the same time?

I'm probably missing something here.

 

[zukikat]

Two thoughts come to mind, but I'm not an expert.
First, I think the expansion valve could be playing a factor and what I think you're seeing in the form of pressure on the low side is just a result of pressure build-up due to ambient outside temperatures since the time you pulled vacuum although I could be mistaken on that.

With the system under vacuum and all electrical connections back to normal, if you try to charge the system with the engine running (and AC button and dash blower fan switch both on), as freon enters the system will the radiator fans and compressor clutch automatically engage at any point as the pressure reaches a high enough level to activate the low pressure switch or have you gotten that far yet?

If it's been sitting a while without a charge and the clutch does eventually engage as you're feeding freon into the system but the system won't actually go low/high to take a charge then the RCV could be stuck, which on my previous TDI would trip the pressure switch to allow the compressor's clutch to engage but the low and high sides would both end up being nearly the same, low side never going low, high side never going high, and it wouldn't take a charge beyond whatever psi is in the charging can/cylinder so it wouldn't cool. Until I replace the RCV the system wouldn't go into suction so it wouldn't take a proper charge even though the clutch was engaged.

 

[cabot]

So, I pulled a vacuum for about an hour and a half. I left it for a couple of hours to make sure that it held vacuum. I then tried to charge it. It is my understanding that you charge it with the valve from gauge to high side closed and gauge to low side open. I connected a can of coolant and the low side went up to 90psi but the compressor never kicks on. I unplugged the connector. 11.8v on one side of the harness plug and continuity to ground on the other. The compressor coil tests good as I described previously.

Is 11.8v enough that it should be turning on? Does an '02 car have voltage at the connector all the time and vary the ground or constant ground and vary the voltage? I have the 3 pin duty cycle type pressure sensor and corresponding FCM. Is it the same on all MKIVs, or do some vary voltage and some ground?

Maybe the RCV is the next thing to try? But my clutch is not engaging. Yours was. Hrmmm.

 

[zukikat]

That's my understanding also, charge it from the low side with the engine running after pulling vacuum and making sure it holds the vacuum for a while.
At some point during the charging process when the pressure builds up enough to trip the pressure switch the clutch ought to engage and then the low side should actually go low (into suction) and the high side should go quite a bit higher unless the RCV is acting up which seems to result in an engaged clutch and running compressor with little or no low side suction and no difference or very little difference between low and high side readings the whole time.

BUT if the clutch isn't engaging, ignore the RCV for now as it's inside the compressor itself.

With the engine running, do the radiator fans start running when you press the AC button on and turn the interior blower fan switch on while there's 90psi on the low side?
The pressure switch apparently uses some sort of PCM modulation signaling instead of being a traditional open/close contact type of on/off switch and mine has never been problematic so I don't know how to troubleshoot it yet.

I'd say double check the psi needed for the pressure switch to engage the clutch and verify normal radiator fans operation under the proper tests as specified in this thread and go from there. It seems like you may still have an electrical gremlin or two since I would've expected the clutch to engage with 90psi although with the high side still in vacuum if I've read your post correctly and your gauge set is working properly on both sides, maybe not.

Also, I once had a bad set of harbor freight ac gauges that the high side was basically unpredictable and totally unusable and another set from harbor freight that was so leaky at the fittings that both gauge sets were useless...
The original set that I got from harbor freight a year earlier with the same exact part number and price tag that was obviously NOT the same item actually worked great but disappeared out of a buddy's car a few weeks before I needed them again and they don't sell that version anymore.

Are you certain the gauge set you're using actually works properly, regardless of whether it may or may not be brand new?

 

[79TA7.6]

So a couple of weeks back I tried to use my AC. I could tell it was kicking off and on every few seconds and I knew this was not normal so I shut it off. This weekend I finally had a chance to do some trouble shooting:

• The compressor is no longer trying to kick on at all.

• My large fan is shot again, just replaced it three years ago.

• My small fan is working on low speed if I jump pins 1 to 2 on the radiator fan temp switch.

• When I test the high speed I get nothing, this is following the directions, key on, AC off, jump pins 2 to 3.

• So I go on to check that the fans itself is good. I jump power to it, both low and high speeds work fine.

From this I am assuming my FCM is bad, correct? If it is bad, but still controlling my fan low speed, would this keep from allowing the compressor to kick on? I am trying to determine this before I go and poke holes in my wire insulation to do anymore diagnosing with the G65 valve.

 

[79TA7.6]

So a couple of weeks back I tried to use my AC. I could tell it was kicking off and on every few seconds and I knew this was not normal so I shut it off. This weekend I finally had a chance to do some trouble shooting:

• The compressor is no longer trying to kick on at all.

• My large fan is shot again, just replaced it three years ago.

• My small fan is working on low speed if I jump pins 1 to 2 on the radiator fan temp switch.

• When I test the high speed I get nothing, this is following the directions, key on, AC off, jump pins 2 to 3.

• So I go on to check that the fans itself is good. I jump power to it, both low and high speeds work fine.

From this I am assuming my FCM is bad, correct? If it is bad, but still controlling my fan low speed, would this keep from allowing the compressor to kick on? I am trying to determine this before I go and poke holes in my wire insulation to do anymore diagnosing with the G65 valve.

Anyone?

 

[zukikat]

So it went from somewhat rapid cycling to not running at all?

If, with the car running, you press the AC button on and turn the blower fan switch on does the one working radiator fan start running?

Have you checked the charge pressure yet?

A melty fuse socket on the battery box fuse block (described earlier in this thread) can cause cycling like that, although there may be other things as well that I'm not aware of.

Beyond the basics I mentionned, if it appears to be electrical then the best approach is to start at the beginning of this thread and follow the steps until you locate and isolate the issue.

 

[79TA7.6]

So it went from somewhat rapid cycling to not running at all?

If, with the car running, you press the AC button on and turn the blower fan switch on does the one working radiator fan start running?

Have you checked the charge pressure yet?

A melty fuse socket on the battery box fuse block (described earlier in this thread) can cause cycling like that, although there may be other things as well that I'm not aware of.

Beyond the basics I mentionned, if it appears to be electrical then the best approach is to start at the beginning of this thread and follow the steps until you locate and isolate the issue.

When I push the AC button with the interior fan on the compressor will not cycle. I do get the AC light on the button to turn on.

With the car running and AC button on, using my cheap gauge I have that screws onto a self fill can, I am reading around 100 psi. This was with an ambient air temp of 85.

I did not see any melted fuses, holders, or wires.

 

[zukikat]

does your one working radiator fan go from off to on with the engine running when you press the AC button on and turn the blower fan switch on?

 

[79TA7.6]

No it does not.

 

[zukikat]

I talked to a friend who has experienced a number of repeated fan/FCM/no AC issues last year who ended up learning a lot about troubleshooting VW AC electrics on a MkIV TDI.
Although usually running when requested and not making any unusual noises, one of his fans was going bad and pulling far too much current, beginning to melt a fuse holder, and randomly upsetting the whole AC system, especially the FCM for multiple reasons...

Apparently your FCM could be bad or he says more like the FCM could just be getting unhappy because of your dead/dying fans which can pull excessive current and cause the FCM to freak out due to potential thermal issues and/or may have also caused the typical melty fusebox socket(s) issue which would then cause intermittent or low voltages that also tend to confuse and upset the FCM to the point that it decides to shut down the AC system and/or fans until it gets reset by a full power cycle (disconnecting the battery for a minute or two and/or unplugging the FCM) and unfortunately on a MkIV there's no way to ask it what it thinks the problem(s) is/are...
If you reset the FCM and your "ac not working" symptoms don't change you can try another FCM first and see what happens before doing further electrical troubleshooting or you can spend more time and dive into the wiring before spending money on another FCM.

For me the main things that are the quickest/easiest steps would be to verify both the low and high side pressures to make sure there's enough for the pressure switch to engage the system, then fix a definitely known issue you have by getting both radiator fans working properly, then verify with a meter that the fuses and sockets on the battery are all working properly, then power cycle/reset the FCM and see if the radiator fans start running with the AC button/fan switch test or not... At that point if the radiator fans still don't run, and especially if the compressor clutch also doesn't engage, try a replacement FCM and see what happens. If none of that solves the problem, then you'll need to follow the steps at the beginning of this thread to go chasing down wiring gremlins and do further in depth troubleshooting.

Side note: This doesn't seem to be the case from your explanation but it still could also be a refrigerant pressure issue, as in a leak which at first can cause the pressure to go from adequate at idle to dropping below the switch threshold as the clutch engages which causes the compressor to rapid cycle like you described until at some point the refrigerant level gets so low that it doesn't activate the pressure switch at all anymore and the compressor no longer operates.

 

[Bartman]

First I would like to say that there is great information posted here!

Most of what I have read in this thread indicates fans not working can cause A/C issues. I have seen a few posts about fans to continue to run after the car is shut off and what could be causing this issue but not saying anything about the A/C. I have a 2001 Jetta TDI and here is my question:

My A/C was working fine yesterday at noon, but when I when I started the car to drive home after work the A/C would not blow cold air. When I arrived home and shut the car off both fans were running on what I believe was high (first time this has happened, I have owned the vehicle for 2 years). In my search of the forum to find possible causes I have not come across someone with the issue of the fans running after car is shut off AND the A/C not working. Can the two be related?
My fans did stop running after 5-10 mins after shutting the car off. I restarted the car to see if the A/C clutch engaged and it did not. After reading some posts I tried starting the car with the A/C off to see what the fans did. They both ran on high and continued to run after I shut the car off. I ended up removing the green fuse to stop them. Again when I arrived at work this morning both fans were running and once again I pulled the fuse (never turned the A/C on this morning). I will trying diagnosing the issue with the fans as per what has been posted on this thread.

Any one know if this is one issue with the Fans and the A/C or do I have two issues and it was just a coincidence they both happened at the same time? I am also going to keep searching for someone who has had a similar issue.

 

[zukikat]

Personally, since you said the fans will eventually stop by themselves, I wouldn't suggest pulling the fuse to stop the cooling fans without knowing for sure what the coolant temperature really is regardless of the potential for battery draining or where the stock temp needle is pointing.
It could be that the car has shut down the AC system on purpose and is running the fans excessively because it thinks there is a significant cooling system problem and it's actually trying to cope with an excessive temperature issue... Or it could be a failing sensor.

What is your actual coolant temperature, not just what the dash temp gauge says.
A ScanGauge is handy for showing real world sensor readings, as is VCDS.

I don't recall my 2001's fans running with the key off although it got destroyed in December and I suffered a bad concussion at the time so my recollection is a bit hazy...

It does sound like either an engine cooling system or sensor problem or likely a FCM related malfunction that could be effecting both systems, although that's just a guess. If you unplug the FCM for a few minutes and plug it back in, does anything start behaving differently?

 

[Bartman]

At the moment I do not know what the actual temperatures is, I have not had a chance to look at the car, hope to start tonight but I have a hectic schedule coming up.

Thank you for the advice of not pulling the fuse, I will try your suggestion of unplugging the FCM plus some other "tests" I have read on the forum. I will post when I have more information.

 

[zukikat]

Not to sound "dire emergency" but I strongly recommend finding out what the coolant temperature is as the fans are running like that "asap" as excessive temperatures can warp aluminum and blow a head gasket and other bad things if it really is a coolant system problem which it may not be but if it were me I'd really want to know...
A ScanGauge II is fairly/somewhat inexpensive and will give you real-time temperature readings and voltage readings, among many other pretty cool things. It's not so useful for boost as its' sample rate is too slow to show surges/spikes but it's a pretty nice tool.

 

[Bartman]

so I was able to look at the car tonight. Started by reading information that DanG144 had posted under thread "Mk IV Manual AC electrical & cooling fan troubleshooting and repair", great post by the way DanG144, thanks! I crawled under the car to locate the FCM and AC condenser, etc. While looking at the condenser I saw a slight dent in it and the two wires have been slightly bared. Then I recalled that I had hit a bad "upheave" in the road during the day yesterday and it would have hit right in that location. I started going through the fuses as Dan suggested and #16 was blown, changed it out and now my AC works. Feel real stupid for panicking and posting on here before I had really looked into the issue. All I have to now is repair the bared wires and I should be good.

Zukikat before I found the fuse issue I let my car cool right down tonight and started it and turned it off and the fans still ran for 5-10 min but now that I have changed the fuse they don't. Maybe this is a good indication that its just a fuse issue. If they happen to continue to run tomorrow after my drive to work (about an hour away) I will repost that they are still an issue, if I don't repost all is good. Thanks for all your advice!

 

[79TA7.6]

I just had Lasik so it will be a little while before I crawl around, in, or under the car. On the positive side it is no longer 100 degrees out.

 

[zukikat]

so I was able to look at the car tonight. Started by reading information that DanG144 had posted under thread "Mk IV Manual AC electrical & cooling fan troubleshooting and repair", great post by the way DanG144, thanks! I crawled under the car to locate the FCM and AC condenser, etc. While looking at the condenser I saw a slight dent in it and the two wires have been slightly bared. Then I recalled that I had hit a bad "upheave" in the road during the day yesterday and it would have hit right in that location. I started going through the fuses as Dan suggested and #16 was blown, changed it out and now my AC works. Feel real stupid for panicking and posting on here before I had really looked into the issue. All I have to now is repair the bared wires and I should be good.

Zukikat before I found the fuse issue I let my car cool right down tonight and started it and turned it off and the fans still ran for 5-10 min but now that I have changed the fuse they don't. Maybe this is a good indication that its just a fuse issue. If they happen to continue to run tomorrow after my drive to work (about an hour away) I will repost that they are still an issue, if I don't repost all is good. Thanks for all your advice!

One of the bared wires could've been completing the circuit until things cooled down or redirecting current into the wrong circuit(s) but it does sound like the problem has been isolated and easy enough to resolve.

I just had Lasik so it will be a little while before I crawl around, in, or under the car. On the positive side it is no longer 100 degrees out.

Follow the doctor's orders and go easy during the healing process. Eyes seem to heal a bit more slowly than other things and it's not worth risking surgical complications to troubleshoot a car's AC problem(s)...
I went from better than 20/20 for many years to suddenly becoming mildly far-sighted over a 6 month period to getting a lot more far-sighted over the past 4 years with mild retina detachment in one eye thrown in for the heck of it and needless to say I have stopped taking my vision quality for granted.

 

[79TA7.6]

For me the main things that are the quickest/easiest steps would be to verify both the low and high side pressures to make sure there's enough for the pressure switch to engage the system, then fix a definitely known issue you have by getting both radiator fans working properly, then verify with a meter that the fuses and sockets on the battery are all working properly, then power cycle/reset the FCM and see if the radiator fans start running with the AC button/fan switch test or not... At that point if the radiator fans still don't run, and especially if the compressor clutch also doesn't engage, try a replacement FCM and see what happens. If none of that solves the problem, then you'll need to follow the steps at the beginning of this thread to go chasing down wiring gremlins and do further in depth troubleshooting.

Side note: This doesn't seem to be the case from your explanation but it still could also be a refrigerant pressure issue, as in a leak which at first can cause the pressure to go from adequate at idle to dropping below the switch threshold as the clutch engages which causes the compressor to rapid cycle like you described until at some point the refrigerant level gets so low that it doesn't activate the pressure switch at all anymore and the compressor no longer operates.

Maybe I am being ignorant, but how would I check the high and low pressures if the compressor is not running? Doesn't the pressure equal out when the system is off?

Is there another way to check the FCM to see if it might be the issue? It turns the fan on low speed but not high. But it will not turn the fan on when I press the AC button.

 

[Whatever210]

I have a ac issue. the ac works great for about 45 min. its ice cold. it almost seems like snow flakes are coming out of the vents it gets so cold. then the ac will stop blowing out the vents. I can hear the blower still running under the passanger side dash. but nothing out the vents. when I pop the hood the large line has condensation on it closer towards the front of the car but on the firewall where the expansion valve is. its frozen solid and theres a lot of ice on it. the larger line has ice on it as well where its connected to the expansion valve. I have to turn off the ac button and let It blow for about 20 min so It will unfreeze then it will function again. it will blow air then I can press the button and it will turn on until it freezes again.

ive been told by somebody that knows ac is that its a temp sensor on the evaporator or something. its not letting the compressor know its cold enough and its not shutting off the compressor. I do notice that the compressor does not cycle. its constantly runs.

where is that part located and how can I test it. ive been told its under the dash. or do you think its another issue like a bad expansion valve. any insight would be helpful! many thanks.

 

[fyrdog]

Hi,

I did read the guide at the beginning but I want to be sure I have it right because it is almost time to spend some big dollars on the AC system.

I checked the fans the Left one was not working so I replaced it with a new one.

Both fans now run with the ignition on , engine off and AC button light on.

I am going to check the pressure in the system tonight.

A month ago the gray foam started coming out the vents.

If the pressure is correct is there a way to by pass something to see if the compressor is good ? I'm thinking the Refrigerant Control is bad.

Should I take a different route first or am I going in the right direction?

Thank You ,
David

 

[zukikat]

Since your fans do run during that test, with the engine running and the dash AC buttons/switches set that same way does your compressor clutch not engage?
When things are working properly the pulley always turns when the engine is running but the pulley only spins the clutch plate when the AC button and blower fan switch are both on while the car is running.

If the radiator fans are running then as far as I know the system's pressure is at least above the absolute minimum to trigger the pressure switch which I believe should also be triggering the compressor clutch to engage when the engine is running and the AC button and blower switch are on unless the electromagnetic clutch coil has gone "open" (less likely) or there's a gremlin in the AC system's electrics (more likely).

If the fans are running and the clutch is engaging but the system isn't cooling there are a number of other things it could be although the RCV and clutch plate retainer nut are the only ones I know much about so far.

Clutch plate retainer nut coming loose is apparently a common Mk4 AC issue although none of the 3 Mk4 TDI's I've owned have suffered enough from that issue to not cool properly so far and only one of them had that issue at all which resulted in a faint and quick metallic chirp sound as the clutch engaged when I pressed the AC button on while driving or as it apparently allowed the clutch to momentarily slip under load at times during really aggressive shifting while the AC was on. Eventually I snugged the nut down as much as I could and that chirp disappeared but cooling was never an issue.

On my car when the RCV failed it was in the minimum displacement position and the charge on the system was incorrect (low) so the fans would run and the clutch would engage but it wouldn't go into suction to take a proper charge, which was obvious on the gauges as the low side never went low and the high side never went high.
I don't know if there are other positions that it can get stuck in or what behavior of the low and high pressures would be in those positions but on my 2001 Jetta the bad RCV made both the low and high side gauges read the same even with the clutch engaged and the compressor running.
The RCV can be ordered on line from numerous vendors for a few bucks less but it was only about $50 with tax included to order from AutoZone, I picked it up the next day, and never having seen or replaced one before it still only took about 30-45 minutes to install without even having to jack up the car although I'm fairly "skinny".
Finding it on their website or in their system at the store isn't easy because they stuck it in the air compressor parts section instead of the automotive AC section for some stupid reason but they do carry it, sometimes have one in stock, and if not can usually have it in your hands the next day.
If you choose to replace the RCV you must pay close attention to how you take everything apart and be certain that you line it all up correctly as you put it back together or bad things can happen but it's really not a hard job as long as you're paying good attention to detail...

As for the foam bits coming out of the vents, in my 2001 Jetta and my buddy's 2000 Golf, when that happened to us it made the heater useless below about 45F, thank goodness for seat heaters, but both of our AC systems seemed to keep on working normally. Mine on hot sunny >95F days did prefer the yellow circle arrow "recirc" button pressed to drop dash vent temperatures down below about 45F but otherwise at night even in >85F weather that AC system would still get the car's interior so cold I'd have to back the hot/cold knob off within a few minutes of my work commute...
In other words, some may disagree but I wouldn't worry about the foam bits yet.

I have seen the interior AC panel develop issues where the hot/cold knob mechanism/cable fail on a buddy's girlfriend's "2.slow" Mk4 which left her car's system blowing warm or hot air all the time even though the system was operating normally and the evaporator coil inside the dash was cooling properly, but as far as I know that's not a common issue so I wouldn't start with that.

 

[zukikat]

I have a ac issue. the ac works great for about 45 min. its ice cold. it almost seems like snow flakes are coming out of the vents it gets so cold. then the ac will stop blowing out the vents. I can hear the blower still running under the passanger side dash. but nothing out the vents. when I pop the hood the large line has condensation on it closer towards the front of the car but on the firewall where the expansion valve is. its frozen solid and theres a lot of ice on it. the larger line has ice on it as well where its connected to the expansion valve. I have to turn off the ac button and let It blow for about 20 min so It will unfreeze then it will function again. it will blow air then I can press the button and it will turn on until it freezes again.

ive been told by somebody that knows ac is that its a temp sensor on the evaporator or something. its not letting the compressor know its cold enough and its not shutting off the compressor. I do notice that the compressor does not cycle. its constantly runs.

where is that part located and how can I test it. ive been told its under the dash. or do you think its another issue like a bad expansion valve. any insight would be helpful! many thanks.

On a home AC system the coil usually ices over due to a low charge or blockage inside the system (happens to the main unit at my office every spring for over 10 years now until they recharge it each spring because my boss is too cheap to pay for finding/fixing the system leak).
I remember reading other posts on this site a long while ago about that same issue like you're experiencing but I don't recall the details. I'm sure you've already searched but I believe the info you're looking for is on here somewhere.

 

[fyrdog]

Thank you for your response.

The Belt does turn the compressor but the clutch does not engage. The cabin fan works and the door to switch from defrost, floor and vent also work to direct the air but it is either heat or ambient temperature depending on where the dash switch is set.

I didn't get to check the pressures as the guy with the gauges and myself couldn't meet up. More my fault than his.

I forgot to post my Jetta is a 2001 TDI. Right around the age where some parts from the previous parts fit and some from later.

Thank you,
David