Check your radiator/condenser fan operation NOW

P2B

Top Post Dawg
Joined
Jan 11, 2006
Location
Toronto & Muskoka, Canada
TDI
2002 Jetta, 2003 Jetta, 2003 Jetta Wagon
I'm probably just going to try and bypass the fuse with an inline fuse holder. I did try and squeeze the contacts back together but that didn't seem to help much.
I would take it as early warning of an impending fuse box meltdown (common on these cars), and swap out the whole thing with a new or junkyard replacement.
 

Richy_T

Veteran Member
Joined
Apr 18, 2007
Location
Dickson, TN
TDI
2000 Jetta
@Richy_T, what about "tinning" the spades of the fuse before bypassing all together? Not sure if you can build up enough solder to account for the relaxed socket.

I am no expert, and do not wanna give bad information, just a thought before you go cutting the factory harness.
That's a good idea actually. I was wondering about thickening them with some copper foil or something but a little solder might work fine. Though it might backfire if the fuse gets hot enough to melt the solder :D
 

Richy_T

Veteran Member
Joined
Apr 18, 2007
Location
Dickson, TN
TDI
2000 Jetta
I would take it as early warning of an impending fuse box meltdown (common on these cars), and swap out the whole thing with a new or junkyard replacement.
I think it's fine. I had a good look when I had the whole thing apart. I may just try tinning the fuse connectors as CantWrite suggested.
 

ray holland

New member
Joined
Jun 23, 2022
Location
falkville,ala
TDI
2003 vw jetta sedan and 2003vw jetta wagon
Th A/C in my 03 Jetta sedan started acting up last year. When I would come to a stop or slow down it seemed to start blowing warm air, until I accelerated down the road, and it would cool off. I figured it needed freon and winter was coming anyways. This year it was working the same as last year so I got a can of freon to put in it. The freon was not going in very fast when I noticed the fuse box on top of the battery smoking and melting. I disconnected the freon, turned the car off and discovered this message forum. Immediately I learned to turn the key to the on position, push the a/c button and turn on the blower motor. That should turn both fans on. I checked that and only the passenger side was working. Then I checked the same thing on my wagon (a/c works and no melting at the fuse box). It had the same 1 broke fan. I quit using the a/c till i could get to the parts store, bought a dual fan unit for the wagon at autozone ($144.00) and went to work. I removed the old fans from the car fairly easily. I then learned that the new shroud and fans could only be used together. The new fans would not fit the old shroud. So, with difficulty I removed the shroud by only taking off the upper radiator hose. Difficult, but doable. Then I squeezed in the new shroud only to find out that one of the bolts for the fan was positioned at a hard a/c line. It was hard to get in but it is in and works fine.
Which puts me back at the sedan. From reading this forum, I'm certain I had the classic signs leading up to compressor fail. I just ordered an a/c kit and another set of fans, but really am interested in suggestions on the melting (alternator?) wire at the fuse box. Could it all be related to my fans and a/c problems? could replacing the fans and compressor fix it?
 

Nuje

Top Post Dawg
Joined
Feb 11, 2005
Location
Island near Vancouver
TDI
2015 Sportwagen; Golf GLS 2002 (swap from 2L gas); 2016 A3 e-tron
2.5L is a Mk5, right?
I'd do a bit more reading before coming to that conclusion, but I gotta think that both fans should be running with the A/C switched on (for all the reasons laid out in the first few posts).
 

norbert77

Veteran Member
Joined
Feb 2, 2022
Location
Petrolia
TDI
01 beetle
I plugged in the vcds and in output activated testing the fan comes on. Just one fan by the look of it.

Is here check to see when fan speed is called for?

Nevermind, I started the car and turned on the AC, fan runs on low
 

Wingnut

Top Post Dawg
Joined
Oct 10, 2002
Location
Toronto & Whitby
TDI
Silver 2003 Jetta Wagon
Hi Everyone. Looking for help with a MKIV Golf that has a A/C system that no longer works.

My daughter came to me and told me her car no longer blows cold. First step, check fuses. All 3 in the left side of dash are good (5, 16 & 25). Then checked fuses on top of battery. Bingo, #3 strip fuse is blown. So to find out why it blew, I check the fans. Large fan was toast. Did not spin freely and must have overheated the circuit to blow the fuse. So easy fix right? New fan and new fuse and should be good to go. Well, not so fast. Still no A/C.

I read Dan's writeup and when I have more time to dig into all the testing, I will check all the pins on the fan control module plugs. In the mean time, I thought I would post here in case someone else had a similar issue and if there is something obvious I am missing.

Things I have done so far:

Changed large fan
Replaced blown fuse
Tested slow speed operation by jumping pins 1 & 2 on temp sensor plug (both fans spin on low)
Swapped out FCM with one from a junk yard in case the old one got fried by the same thing that blew the fuse.
Checked resistance on the A/C clutch - 4 ohms as it should be.
Checked for voltage at the clutch plug. Only 4v (should be 9v IIRC)

I've given up for today as I need to get some sleep, but will dig back into it tomorrow.

Thanks for reading.
 

SilverGhost

Veteran Member
Joined
Mar 25, 2005
Location
Back in So Flo - St Lucie
TDI
'05 Golf - totaled :(, wife's '13 Beetle - buy back, TDIless
I would hazard a guess that the system over pressured with the blown fan and released Freon. If it kept working for a while like this its also possible the compressor is worn/shot. At the very least once the pressure relief valve triggers it needs to be replaced.

Jason
 

P2B

Top Post Dawg
Joined
Jan 11, 2006
Location
Toronto & Muskoka, Canada
TDI
2002 Jetta, 2003 Jetta, 2003 Jetta Wagon
I will check all the pins on the fan control module plugs. In the mean time, I thought I would post here in case someone else had a similar issue and if there is something obvious I am missing.
If the fans run with ignition and AC switch on, but the compressor clutch doesn't engage, next thing to check is FCM inputs. Pressure sensor input should read about 2.5v AC if the system has a full charge. Don't assume you have fan power to the FCM just because the fuses are good, my issue was a bad crimp at the FCM power input pin
 

Wingnut

Top Post Dawg
Joined
Oct 10, 2002
Location
Toronto & Whitby
TDI
Silver 2003 Jetta Wagon
I would hazard a guess that the system over pressured with the blown fan and released Freon. If it kept working for a while like this its also possible the compressor is worn/shot. At the very least once the pressure relief valve triggers it needs to be replaced.

Jason
This is the logical diagnosis. Fans work when bypassed jumping pins on temp sensor plug. They do not work when ignition is on and AC button pushed. I checked voltage at G65 and only got 0.6v. According to Dan's Guide, it should be over 2v. So looks like low refrigerant pressure.

If the pressure got too high and the pressure relief valve dumped it, is it a fail and replace type of valve, or does it reset? Is this the valve on the back of the compressor?

Valve.jpg
 

Leadbettr

Member
Joined
May 20, 2022
Location
Tucson
TDI
Golf 03 TDI
I'm looking for some confirmation. I've followed DanG's fan mechanics guide "A4_Coolant_Fan_testing_Rev_7" and I'm not getting slow speed from my fans. When I jump at the thermo 1&2 I get nothing. 2&3 gives me high speed.
There's a new fuse box on top of the battery (they old one melted), all fuses inside and out are good and clean, there's a new FCM, new fans, the ac button lights up, the compressor clutch engages when I toggle the ac button. New cabin filter. Interior fan blows strong warm air, I replaced the interior blower fan a while back when it failed. There's no cold air even on the freeway. I don't struggle with engine overheating.

The history of the ac system; it was working fine. Then the s180 fuse melted. I replaced the fuse, then the box and all fuses. The passenger fan smoked and smelled at some point and I replaced them both. The ac continued to run then sometime after, then it unceremoniously didn't. Then I replaced the FCM with one from Idparts.

I've been reading a bunch of forums on this and my head is spinning, so I'm reaching out for some guidance if you'd have me.

I was advised extremely off hand from a vw mechanic at Top Shop that the refrig pressure sensor /could/ be the issue. I haven't walked down the ac side of the system (A4_Air_Conditioning_Troubleshooting_Rev_7) since it seems to be a fan mechanism issue based on what can gather from "A4_Coolant_Fan_testing_Rev_7" with no slow fan.

My next step is to try and dye the refrigerant and look for leaks and check voltages at the four plug coming into the new FCM.

I'd very much appreciate some input, positive and productive preferred. I'm already aware I'm an idiot. Thank you.
 

Nuje

Top Post Dawg
Joined
Feb 11, 2005
Location
Island near Vancouver
TDI
2015 Sportwagen; Golf GLS 2002 (swap from 2L gas); 2016 A3 e-tron
I got a set of gauges ("manifold") last year trying to chase down similar problem. I don't trust my understanding of the actual refrigeration process to actually fill it and whatnot, but for just testing whether or not I have refrigerant pressure....does the trick.
(Having had to replace the compressor, it was obviously empty. $200 later at VW, they did a vacuum test and re-filled. All good.
Until a week later and I had no A/C again (and no spinning fans). Hooked up the manifold gauges and read zeroes across the board.
$500 more at VW.....all good. For fewer than five days. Same thing again. And thus explains why I eschew dealer servicing if in any way possible).
 

P2B

Top Post Dawg
Joined
Jan 11, 2006
Location
Toronto & Muskoka, Canada
TDI
2002 Jetta, 2003 Jetta, 2003 Jetta Wagon
My next step is to try and dye the refrigerant and look for leaks and check voltages at the four plug coming into the new FCM.
I'd say you are on the right track. I assume you have verified the fans work on low when powered directly, but they don't when jumpered at the thermoswitch. Fuse is good so power is going missing somewhere in the harness, and the 4 pin power plug at the FCM is the next place to check.

Compressor is engaging, so there is enough pressure in the system to produce at least some cooling.
 

Genesis

Top Post Dawg
Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
Note that if there is no refrigerant in the system the compressor will not engage and the fans will not run. If the compressor comes on then the pressure sensor is telling the ECU that there is pressure in the system and thus that is eliminated as a cause.

Be warned that if you put gauges on the service ports and they haven't been checked in a while you better have two more service ports standing by. It is NOT uncommon for the little ball that seals in there to disintegrate when you check it after many years, and if that happens you will lose everything in the system immediately. That now means a dryer replacement is required UNLESS you have new ports you can immediately replace the dead ones with, draw a vacuum and recharge.

Check the low speed terminals on the fans by directly putting 12V power on them (Fused! They can be shorted!) at the plug that goes to each fan. The low-speed side of these fans almost always fails first because its simply a dropping resistor (I guess a PWM drive circuit cost too much) and they burn up.
 

Leadbettr

Member
Joined
May 20, 2022
Location
Tucson
TDI
Golf 03 TDI
I'd say you are on the right track. I assume you have verified the fans work on low when powered directly, but they don't when jumpered at the thermoswitch. Fuse is good so power is going missing somewhere in the harness, and the 4 pin power plug at the FCM is the next place to check.

Compressor is engaging, so there is enough pressure in the system to produce at least some cooling.
I actually didn't directly test the fans. I was too preoccupied with testing the FCM. I'll do that first thing.
Yeah I can see the clutch on the compressor starting when I press the AC button. But I see no cooling from the air coming out of the vents, even at highway speeds.

Note that if there is no refrigerant in the system the compressor will not engage and the fans will not run. If the compressor comes on then the pressure sensor is telling the ECU that there is pressure in the system and thus that is eliminated as a cause.

Be warned that if you put gauges on the service ports and they haven't been checked in a while you better have two more service ports standing by. It is NOT uncommon for the little ball that seals in there to disintegrate when you check it after many years, and if that happens you will lose everything in the system immediately. That now means a dryer replacement is required UNLESS you have new ports you can immediately replace the dead ones with, draw a vacuum and recharge.

Check the low speed terminals on the fans by directly putting 12V power on them (Fused! They can be shorted!) at the plug that goes to each fan. The low-speed side of these fans almost always fails first because its simply a dropping resistor (I guess a PWM drive circuit cost too much) and they burn up.
Like I said above I'll check out the fans directly, thanks. How much would you fuse it, 30 amp?

The mechanic did a super short "test" to see if there was any gas in the system by tapping the low pressure port. Nothing came out. That's when he suggested what he did, sensor, etc... I soon after this moment I checked the low side with a can filler gauge and saw zero. Here's the controversial part, I used a can of gas to recharge the system. Just a small amount. The assumption was at 350k mostly in AZ this has been done before. Here we are. The gauge will read 30 psi on the low port when the compressor is on and 50+ when it off post recharge. Then zero some time later.

None of ac system side (vs the fan/FCM) was touched when it went warm initially.

So I should replace both ports and the drier. Then recharge the system?

Thanks for your time.
 

Genesis

Top Post Dawg
Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
Well, zero is zero..... Above 30psi or so on the low side (there is only ONE pressure sensor, on the high side, so then the system is not running it reads the equalized pressure) the system should come on. If the compressor runs the low speed fan enable circuit is also on. High speed is engaged either from the thermoswitch or the ECU seeing high pressure on the refrigerant pressure sensor.

30A inline fuse for test leads is fine. I'd also test the leads with an ohmmeter first; quite low is normal (motors read very low when not turning) but a dead short is not. I have a bench power supply that is current-limited that I use for things like this; it will fold back and complain rather than blow something up if there's a short.

If refrigerant is leaking out then you have to find and fix the leak. I'd put a can of refrigerant in there with dye in it, run it a few minutes and then go look with a black light. Wherever its leaking will likely glow like a Christmas tree. Don't be surprised if its the condenser or evaporator, although the shaft seal on the compressor can leak as well -- or the service ports IF DISTURBED, and you have, are fairly common too. The hoses and O-rings, unless disturbed or the hoses are damaged, are quite a bit less-common. In any event the UV dyed refrigerant and a black light (or a refrigerant sniffer if you have one) will show you where it is. If the unit is at atmospheric pressure you must assume that the drier is toast. Beware not taking care of that; moisture + the refrigerant and oil makes an acid over time which will eat everything, including the evaporator and then you're ripping the dashboard out to get to it for replacement. NOT fun.

Note that the service ports are a bit tricky to replace only because its not obvious if you haven't changed them before. If they're not leaking leave them alone, but DO have a set in your toolbox -- they're cheap and if you have 'em and need 'em, well, you need 'em. The hex on the port and that on the pipe ARE DISTINCT but don't look that way if you're not careful, and you have to counterhold the pipe hex because its aluminum and will snap if you don't. The ports are NOT in tightly; the seal around the bore is made with an O-ring, not from being cranked down.

The drier must NOT be allowed to be exposed to the atmosphere until it is installed and then immediately evacuated. It will be ruined by atmospheric moisture in less than a half-hour if the ports are uncovered so it takes some finesse to change it as you have to be prepared to immediately pull vacuum (and being able to flush with moisture-free gas, usually nitrogen although a tank of scuba air works too since that's a -50F or better dew point, if you have the regulator for it, is a really good idea.)
 
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Leadbettr

Member
Joined
May 20, 2022
Location
Tucson
TDI
Golf 03 TDI
Well, zero is zero..... Above 30psi or so on the low side (there is only ONE pressure sensor, on the high side, so then the system is not running it reads the equalized pressure) the system should come on. If the compressor runs the low speed fan enable circuit is also on. High speed is engaged either from the thermoswitch or the ECU seeing high pressure on the refrigerant pressure sensor.

30A inline fuse for test leads is fine. I'd also test the leads with an ohmmeter first; quite low is normal (motors read very low when not turning) but a dead short is not. I have a bench power supply that is current-limited that I use for things like this; it will fold back and complain rather than blow something up if there's a short.

If refrigerant is leaking out then you have to find and fix the leak. I'd put a can of refrigerant in there with dye in it, run it a few minutes and then go look with a black light. Wherever its leaking will likely glow like a Christmas tree. Don't be surprised if its the condenser or evaporator, although the shaft seal on the compressor can leak as well -- or the service ports IF DISTURBED, and you have, are fairly common too. The hoses and O-rings, unless disturbed or the hoses are damaged, are quite a bit less-common. In any event the UV dyed refrigerant and a black light (or a refrigerant sniffer if you have one) will show you where it is. If the unit is at atmospheric pressure you must assume that the drier is toast. Beware not taking care of that; moisture + the refrigerant and oil makes an acid over time which will eat everything, including the evaporator and then you're ripping the dashboard out to get to it for replacement. NOT fun.

Note that the service ports are a bit tricky to replace only because its not obvious if you haven't changed them before. If they're not leaking leave them alone, but DO have a set in your toolbox -- they're cheap and if you have 'em and need 'em, well, you need 'em. The hex on the port and that on the pipe ARE DISTINCT but don't look that way if you're not careful, and you have to counterhold the pipe hex because its aluminum and will snap if you don't. The ports are NOT in tightly; the seal around the bore is made with an O-ring, not from being cranked down.

The drier must NOT be allowed to be exposed to the atmosphere until it is installed and then immediately evacuated. It will be ruined by atmospheric moisture in less than a half-hour if the ports are uncovered so it takes some finesse to change it as you have to be prepared to immediately pull vacuum (and being able to flush with moisture-free gas, usually nitrogen although a tank of scuba air works too since that's a -50F or better dew point, if you have the regulator for it, is a really good idea.)
Fantastic information. Exactly the level of help I'm looking for. Thank you.

I just put in dye and heard a massive hiss coming from near the drier. So I guess that's my issue. I don't know why I didn't hear it before. It'll won't be dark enough for the uv light here for 5 or so more hours, until then any speculation on what failed?
Despite, I assume I'll need to order a new drier. I'll do that now. The new high pressure sensor is here but I haven't installed it yet. Nor have I had a moment to check the voltages or fans directly. Hopefully this evening when I'm looking for the dye.
I haven't checked with VCDS yet. Are there any tests or info I can get from that end?
 

Genesis

Top Post Dawg
Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
Well, don't bet on it being the drier, although it could be. Its right near the condenser on that side and that may be what's leaking, or the hard pipes. The drier is just a hunk of metal with two ports and a couple O-rings for seals on the pipes that go into it.
 

norbert77

Veteran Member
Joined
Feb 2, 2022
Location
Petrolia
TDI
01 beetle
My GMC duramax Van was just in an AC shop, They said the shredder valve was was leaking leaking. If you gotta hiss, you probably have an Orange that gave up the ghost
 

Leadbettr

Member
Joined
May 20, 2022
Location
Tucson
TDI
Golf 03 TDI
Note that if there is no refrigerant in the system the compressor will not engage and the fans will not run. If the compressor comes on then the pressure sensor is telling the ECU that there is pressure in the system and thus that is eliminated as a cause.

Be warned that if you put gauges on the service ports and they haven't been checked in a while you better have two more service ports standing by. It is NOT uncommon for the little ball that seals in there to disintegrate when you check it after many years, and if that happens you will lose everything in the system immediately. That now means a dryer replacement is required UNLESS you have new ports you can immediately replace the dead ones with, draw a vacuum and recharge.

Check the low speed terminals on the fans by directly putting 12V power on them (Fused! They can be shorted!) at the plug that goes to each fan. The low-speed side of these fans almost always fails first because its simply a dropping resistor (I guess a PWM drive circuit cost too much) and they burn up.
Egg on my face. Could it be that simple?

Nothing....when I directly power the middle wire on both fans (#2&3?) and Ol on my multimeter (overload) when I check the resistance.
High fans when I power the wire on the flat side (#1&3?) and zero resistance. This whole time...I've just had blown resistors?

Then where's that hiss coming from then? There was no dye except on the low pressure valve nipple when I checked with the black light this evening.

Should I just replace the fans then?
Ya'll think they'll burn out again? What's the move?
 

Leadbettr

Member
Joined
May 20, 2022
Location
Tucson
TDI
Golf 03 TDI
Egg on my face. Could it be that simple?

Nothing....when I directly power the middle wire on both fans (#2&3?) and Ol on my multimeter (overload) when I check the resistance.
High fans when I power the wire on the flat side (#1&3?) and zero resistance. This whole time...I've just had blown resistors?

Then where's that hiss coming from then? There was no dye except on the low pressure valve nipple when I checked with the black light this evening.

Should I just replace the fans then?
Ya'll think they'll burn out again? What's the move?
So out of curiosity I wired the middle (low speed) wire of the small fan to the high speed wire of the small fan. That caused both fans to run when I jump the plug from the thermo. Actually jumping both low and high speeds work in this modification at the thermo plug. But the fans don't run on low when everything is assembled and the key/ac button is switched on. And I ran the engine/ac and got no cold air.

Update;
I then proceeded to attempt to top off the gas and it won't take anymore than 30 psi running and 50psi stopped at the low pressure valve.
But now the slow fans come on, both with the engine/ac on and when the engine is off but key/ac is on. Though it's not blowing cold air.

The compressor is kicking on and off clearly when I toggle the ac button.

I don't hear anymore hissing. Still no christmas trees under the hood. Just a false positive from the slight corrosion on the alternator.
 
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Leadbettr

Member
Joined
May 20, 2022
Location
Tucson
TDI
Golf 03 TDI
So out of curiosity I wired the middle (low speed) wire of the small fan to the high speed wire of the small fan. That caused both fans to run when I jump the plug from the thermo. Actually jumping both low and high speeds work in this modification at the thermo plug. But the fans don't run on low when everything is assembled and the key/ac button is switched on. And I ran the engine/ac and got no cold air.

Update;
I then proceeded to attempt to top off the gas and it won't take anymore than 30 psi running and 50psi stopped at the low pressure valve.
But now the slow fans come on, both with the engine/ac on and when the engine is off but key/ac is on. Though it's not blowing cold air.

The compressor is kicking on and off clearly when I toggle the ac button.

I don't hear anymore hissing. Still no christmas trees under the hood. Just a false positive from the slight corrosion on the alternator.
So.
I found the hissing.
Perhaps the gas can I was using previously was too low to get enough pressure to show the crack.
The condenser is leaking from inside the radiator sandwich on one of what perhaps is called a "Reservoir" (the thick tubes where the coils would be making their u-turns). I can't get a photo until after I replace it. I have a new Nissens (is back ordered) TYC condenser and drier from idparts in the mail.
Any idea how I could get a leak/crack in such a protected area?

On a separate note the slow speed fan issue seems to be fixed by my wiring bypass? When the system pressure was high enough the slow speed fans would come on key/ac button on, engine off.

Should I swap out the high pressure sensor for the new one or leave the old one?

When the ac was pressured and leaking the ac never got cold even by a degree, is there something else that's failed or am I thinking too far ahead. I do remember the MK4 ac cools pretty quickly...
 
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Genesis

Top Post Dawg
Joined
Feb 26, 2003
Location
Sevier County TN
TDI
'03 Jetta Wagon
Age, or someone recharged the unit after a complete loss of pressure without purging and replacing the drier -- in which case you have acid damage everywhere and more trouble to come.
 
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