Check your radiator/condenser fan operation NOW

Doug71

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Just wanted to say thank you for this post.. I was able to trouble shoot my AC issues.. It was the 30amp on the battery that was blown.. Now my AC is Ice Cold which has not been true for over a year.. YAY.. Thank you again for this great post.. Now for the climatronic AC upgrade.
 

GD

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DanG144 said:
I understand that the voltage to your AC clutch is pulsating.

Assuming the fans are operating in slow, not fast, that would seem to rule out the High pressure sensor or thrust sensor.

It could still be the FCM, or the FCM responding to a cutoff signal from the ECU, or a clutch coil that is too low in resistance (shorted) and drawing too much power.

What voltage are you seeing to your compressor? And are you measuring it with the clutch coil hooked up? Or with some other resistive load on the circuit?
Just checked the voltage with the AC unit switched on nothing else. Didn't measure volts just hooked up a light/power tester. Fans seemed to run fast will have to check that they are running at both speeds is there a way to check what speed they are running at? Will the old large fan seizing up and the small one losing one of its speeds and the strip fuse being replaced have caused any malfunction to other parts of the AC system? These components were replaced but this problem persists.

Thx
 

DanG144

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If the fans are running in fast, then we are back to potentially having a bad High pressure sensor/switch (AC thrust transducer.) Do the fans come on in fast as soon as you turn the key on? Or do you have to turn on the AC?

The only way I know to tell fast from slow is by ear; even if I had a strobotach I do not know the rpm. You can use the thermoswitch jumpering test from one of the pdf's in post #1 to run them in both speeds to test your ear.
 

andrewvanh

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I followed through your guides and ran into one problem. My fans don't kick on when the system is turned on. I jumped them with the radiator temp switch and they both turn on at low and high speeds. I checked all voltages from the fuses and they are good. S180 is good. T4/3 doesn't have any power on it. I have tried to measure it multiple places. The wire coming out of S180 has voltage on it. Everything I read says that S180 runs directly to T4/3. The wire coming out of S180 is solid red. The wire going to T4/3 has a black stripe. It is the same guage and color as the wire on T4/1. Any help would be appreciated. I am having problems with ebahn and can't pull up the wiring diagram for this. Thanks.


Can someone tell me how the wiring makes it from S180 to the T4/3 on the FCM? This is where my problem is.
 
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Flatliner

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DanG144 said:
There is no switch on the low pressure side of the system, you are correct.

On your car, there is no high pressure switch either. There is a pressure sensor on the high side that sends a duty cycle signal proportional to pressure to the Fan Control Module. I have to wonder how your mechanic checked out the high pressure switch...The way the sensor should be checked is to read the output of the sensor and compare it to the system pressure. They should correspond. A table is provided in one of the links at the bottom of post #1.

Can you tell if your fans are running in fast speed or slow speed? Can you compare them to someone elses?

If your pressure sensor is sending a low signal, the FCM would lock out your fans and the clutch.

(If your pressure signal is in the normal range the FCM runs the slow speed fans and allows the clutch to engage. If it gets to a high pressure condition the FCM should shift the fans to fast and still allow clutch engagement.)

If your pressure sensor is sending a HI-HI pressure signal the FCM leaves your fans in fast and locks out the clutch.

If your ECR senses high coolant temperature it will turn the fans on high and turn off your clutch (via the FCM).

If your ECR senses heavy engine load (full throttle) it will turn off the clutch via the FCM.

So, yes the FCM can fail in such a fashion that it does not energize your clutch, but it could also be working properly.

If I were you, I would test my fans response to the thermoswitch, then go through the AC troubleshooting guide. If your fans work normally from the thermoswitch, I would be more likely to suspect a clutch or wiring issue than the FCM.

But there are really no shortcuts to the troubleshooting.


Here I am almost a year later and still no A/C shame on me! I finally had it last week when it was way too hot for me. I had stopped trouble shooting because I didn't have a way to test the duty cycle on the G65 sensor. So this morning, I just picked one up and put it on the car and crossed my fingers... but still nothing:(

As I continued through the pdf, this is where I got a little more confused. Step 5 through the end, does the car have to be running still or just in ignition on, a/c on and fan on first setting?

So here is where I am at tonight, car is cold, but car is running, radiator fans on low with A/C on and cabin fan on first setting, no clutch engagement. I disconnected the plug to the compressor and measured voltage. I read 4.18V... then it would double to a lil over 8 and go back to 4.18V, but never made it to 9.5V. Question 1: do I still need to measure with load or is it safe to say, there is just not enough voltage to turn compressor clutch on? After checking the voltage, I shut the car off and even at my lowest setting, unplugged, measuring compressor side, I get 1 for the resistance, you stated 4 ohms, so is mine broken lol? Question 2: should this be done with car on? I don't think it matters because we are measuring resistance using multimeter, right?


Steps 6 through the end I checked with the car not running disconnected the harness for T14, then put key in ignition, AC button on and fan on 1st setting, Question 3: is this correct or should the car be running this whole time?

T14-8, had a little less than 12V, 11.75
T14-9, had 12V
T14-4, had 12V
T14-6, had trouble reading resistance, maybe because of my ground, but eventually got .5 ohm
T14-14 and T14-5, i had beep for continuity
T14-2, here we go again with the duty cycle... I can't measure, do I need a new multimeter :confused:

T14-3 is where I stopped... it's getting late and I need to get some sleep, but part of the reason, is I was starting to not understand at this point. When I check for the pulsing voltage, what should it be... or am I just looking for on/off to see if FCM is not allowing it to turn on? More duty cycle talk :( then you mention "throttle basic settings" what is this and why would I lose what was orignally there?

Last thing you mention is that I can provide voltage on pin 1 while grounding pin 2 to test a/c clutch, this is on the compressor plug correct?

Dan, thanks in advance for the help and patience with all of us. If I can't figure this out in the next few days, I may just have to bite the bullet and take to dealer :(
 

DanG144

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Flatliner said:
Here I am almost a year later and still no A/C shame on me! I finally had it last week when it was way too hot for me. I had stopped trouble shooting because I didn't have a way to test the duty cycle on the G65 sensor. So this morning, I just picked one up and put it on the car and crossed my fingers... but still nothing:(

As I continued through the pdf, this is where I got a little more confused. Step 5 through the end, does the car have to be running still or just in ignition on, a/c on and fan on first setting?

So here is where I am at tonight, car is cold, but car is running, radiator fans on low with A/C on and cabin fan on first setting, no clutch engagement. I disconnected the plug to the compressor and measured voltage. I read 4.18V... then it would double to a lil over 8 and go back to 4.18V, but never made it to 9.5V. Question 1: do I still need to measure with load or is it safe to say, there is just not enough voltage to turn compressor clutch on? After checking the voltage, I shut the car off and even at my lowest setting, unplugged, measuring compressor side, I get 1 for the resistance, you stated 4 ohms, so is mine broken lol? Question 2: should this be done with car on? I don't think it matters because we are measuring resistance using multimeter, right?


Steps 6 through the end I checked with the car not running disconnected the harness for T14, then put key in ignition, AC button on and fan on 1st setting, Question 3: is this correct or should the car be running this whole time?

T14-8, had a little less than 12V, 11.75
T14-9, had 12V
T14-4, had 12V
T14-6, had trouble reading resistance, maybe because of my ground, but eventually got .5 ohm
T14-14 and T14-5, i had beep for continuity
T14-2, here we go again with the duty cycle... I can't measure, do I need a new multimeter :confused:

T14-3 is where I stopped... it's getting late and I need to get some sleep, but part of the reason, is I was starting to not understand at this point. When I check for the pulsing voltage, what should it be... or am I just looking for on/off to see if FCM is not allowing it to turn on? More duty cycle talk :( then you mention "throttle basic settings" what is this and why would I lose what was orignally there?

Last thing you mention is that I can provide voltage on pin 1 while grounding pin 2 to test a/c clutch, this is on the compressor plug correct?

Dan, thanks in advance for the help and patience with all of us. If I can't figure this out in the next few days, I may just have to bite the bullet and take to dealer :(
answer 1. You do not need to measure with a load, that is not enough voltage for the clutch. 1 ohm across the pins for the compressor clutch is too low. It should be 4 ohms. Inaccurate readings at low resistance is a common problem with some meters. Touch the ends of your leads together on the lowest resistance scale. Take that reading (if it is above zero) and add it to what ever you read. If the reading is below zero with the leads touching, try another ohmmeter. If your resistance is really 1 ohm, you may have also damaged your FCM from over current.
Answer 2, Check clutch resistance with the car off.
Answer 3, check from step 6 on with engine off, key on, cabin fan in slow, AC on. EXCEPT when checking the ground resistance; that must be done with the key off. Thanks for pointing this out. Rev 8 coming up.

So concentrate on the seemingly bad clutch coil. Skip on down and check what it does when you put the 12 volts across its two pins, momentarily. Use a fused power source. (Say off of the plug for the radiator thermoswitch, if you have another 30 amp fuse.)

The signals from the ECU are problematic; I would have trouble judging them myself. I really need to check them with an o-scope to see what is normal. All I could do was try to tell you what I got on my own (well running) AC system.

I have yet to find a car that had lost its basic throttle settings, but one person reported that fixed his. I think it a VERY low probability, if your car drives well.

Are your radiator fans running normally in slow speed when the AC is on?
 

andrewvanh

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Could my fans work correctly when jumpering the radiator temp switch but I am still missing the voltage on pin T14/3? I doubt this is possible but tried measuring it multiple times and can't see a voltage. Ebahn isn't showing the wiring diagrams. I keep getting a red x on them.
 

DanG144

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Yes, I suspect so.

That voltage/signal on t14/3 from the ECU is uncertain. I suspect that it could be anything but grounded, and still allow normal operation.

Do your fans work correctly in slow and in fast from the thermoswitch?

Can you tell me your symptoms? What do the fans do when the AC is turned on (with key off, cold car.)
 

andrewvanh

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DanG144 said:
Yes, I suspect so.

That voltage/signal on t14/3 from the ECU is uncertain. I suspect that it could be anything but grounded, and still allow normal operation.

Do your fans work correctly in slow and in fast from the thermoswitch?

Can you tell me your symptoms? What do the fans do when the AC is turned on (with key off, cold car.)
When jumpering the thermoswitch both fans work correctly on slow and fast.

When the AC switch is turned on regardless of the key state the fans do not turn on. I am not getting my cold air. The car is a 2003 ALH. I have voltage going into the compressor clutch but didn't Ohm it out.
 

GD

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DanG144 said:
If the fans are running in fast, then we are back to potentially having a bad High pressure sensor/switch (AC thrust transducer.) Do the fans come on in fast as soon as you turn the key on? Or do you have to turn on the AC?

The only way I know to tell fast from slow is by ear; even if I had a strobotach I do not know the rpm. You can use the thermoswitch jumpering test from one of the pdf's in post #1 to run them in both speeds to test your ear.
I have to switch the AC on for the fans to kick in. Like you say its a bit of a judgement call to see if the fans are running on fast or slow though.
 

Flatliner

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Again thank you.
DanG144 said:
... 1 ohm across the pins for the compressor clutch is too low. It should be 4 ohms. Inaccurate readings at low resistance is a common problem with some meters. Touch the ends of your leads together on the lowest resistance scale. Take that reading (if it is above zero) and add it to what ever you read. If the reading is below zero with the leads touching, try another ohmmeter. If your resistance is really 1 ohm, you may have also damaged your FCM from over current.
Answer 2, Check clutch resistance with the car off.
I must have been exhausted, because I went back to measure this morning before I left for work the resistance on the T14 harness ground again and it read .5 ohms (confirms my multimeter worked), so I checked the compressor again and it reads 1, infinity, not 1 Ohm. I can only assume this is not good news. It seems on my multimeter with the leads not connected to anything, reads infinity. I then measured the ground, it moved to .5, but the compressor measurements had no change from infinity.

...Answer 3, check from step 6 on with engine off, key on, cabin fan in slow, AC on. EXCEPT when checking the ground resistance; that must be done with the key off. Thanks for pointing this out. Rev 8 coming up.
Thanks.

So concentrate on the seemingly bad clutch coil. Skip on down and check what it does when you put the 12 volts across its two pins, momentarily. Use a fused power source. (Say off of the plug for the radiator thermoswitch, if you have another 30 amp fuse.)
I'll have to do this next to see what happens, should this be done with car running or off? If off, won't the pulley try to engage and spin on the belt?

......Are your radiator fans running normally in slow speed when the AC is on?
I believe they were, but something happened today on way to work and wife confirmed it happened to her before. The blue coolant light turned back on after about 15 minutes of driving after it had shut off from the initial warm up, would this effect the A/C system? Wife said when it happened to her, it did this, then flashed for a bit, then it went away.

I have a ROSS VAGCOM, so I will have to check to see if any codes are thrown tonight as well.

At this point, if I were to take it to a dealer, how would they diagnose the A/C, following similar instructions? Just wonder what they would do different if I decide to go that route.

Thanks again, Dan.
 

DanG144

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Check your coolant level, ensure you are not skirting the low limit, and are not losing any coolant.

If you are overheating, or the ECU thinks you are overheating (due to a bad coolant temperature sensor) it can turn off your AC. But I don't think the blue light means overheating, does it? (check your manual.)

Infinite coil resistance means that it will not work.

You can still try to jump power to it; it will not hurt anything to do it momentarily - as long as the center portion of your AC pulley turns with finger pressure. This will just confirm that the coil is bad. This is normally done with the engine on so you can see the center of the pulley start to turn if the clutch latches in.
 

dbhyslop

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I'll post this here because it's one of the more widely followed AC threads.

I usually avoid Harbor Freight like the plague, but I couldn't turn down this price. When I took these out of the box they actually didn't look that bad. Typically you can tell a HF tool is going to fail just by looking at it. While I'm sure neither of these are up to the quality of the professional tools, they seem like they'll do for an occasional DIY'er.
Dan
 

dqa

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My "High Low Pressure Switch" (per Impex), aka part 1h0959139b exploded today, leaving the electrical connector dangling, the 4 metal contacts easily visible on the mount with the system, and lots of greenish refrigerant fluid leaking out.

The part ID label fell off and was on the ground with the broken ring-shaped piece that apparently secured the two parts together; I'm guessing that will need to be replaced. What other steps do I need to take?

Is there any chance that it's just the switch that gave up the ghost after 11 years and 275k miles? I think I know the answer to that. BTW, compresser and drier was replaced ~6 years ago.
 

MAXRPM

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Dan nice write up about A/C, now it's time to check my fans summer is around the corner.
 

DanG144

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dqa said:
My "High Low Pressure Switch" (per Impex), aka part 1h0959139b exploded today, leaving the electrical connector dangling, the 4 metal contacts easily visible on the mount with the system, and lots of greenish refrigerant fluid leaking out.

The part ID label fell off and was on the ground with the broken ring-shaped piece that apparently secured the two parts together; I'm guessing that will need to be replaced. What other steps do I need to take?

Is there any chance that it's just the switch that gave up the ghost after 11 years and 275k miles? I think I know the answer to that. BTW, compresser and drier was replaced ~6 years ago.
Several folks have gotten away with just installing a new switch or hp sensor, evacuating and recharging in similar circumstances.

Others have replaced the drier and switch. If you ever get free air flow into your system, you should replace the drier. If you still have some refrigerant pressure, then you should not need to.

Unscrew your HP sensor as soon as possible. This will let the scrader valve close and prevent air intrusion.

Good luck.
 

DanG144

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dqa said:
My "High Low Pressure Switch" (per Impex), aka part 1h0959139b exploded today, leaving the electrical connector dangling, the 4 metal contacts easily visible on the mount with the system, and lots of greenish refrigerant fluid leaking out.

The part ID label fell off and was on the ground with the broken ring-shaped piece that apparently secured the two parts together; I'm guessing that will need to be replaced. What other steps do I need to take?

Is there any chance that it's just the switch that gave up the ghost after 11 years and 275k miles? I think I know the answer to that. BTW, compresser and drier was replaced ~6 years ago.
Also be darn sure that both of your fans are working, (and run when you have a charge in the system). These switches/sensors usually do not fail like this unless they are seeing much higher than normal pressures - which either means overfill of refrigerant, or much higher than normal temperatures.
 

Mass. Wine Guy

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Both fans in my Golf work, only one in my Jetta. That's because the plastic cap to some jug got sucked up and stuck in the fan blades, burning out the motor and control module. If I use the A.C. while driving at normal speeds, my understanding is that there will be enough air flow through the system to prevent problems. If I got stuck in raffic, I'd turn the A.C. off.

Fixing this is labor intensive and would cost around $500 or more, I'm told. Not worth it for the six or so times a year I use the A.C. in this car.
 

DanG144

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Essentially, you are correct, if by normal speeds you mean on the highway. Running with a single fan in town will result in higher than normal system temperatures and pressures, shortening the life of your AC system.

But a replacement fan is more like $40 to $80 for an A4. Some folks here have spent $110 for a set of two from Advance Auto and some other sources. A5 fans are much more expensive, so far.

And the labor is not so much. Less than 2 hours for a novice on a Jetta.

The downside is that you will have no warning when the last fan fails. Even one stoplight with no fans will result in too high an AC system temperature and pressure.
 

dqa

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DanG144 said:
Also be darn sure that both of your fans are working, (and run when you have a charge in the system). These switches/sensors usually do not fail like this unless they are seeing much higher than normal pressures - which either means overfill of refrigerant, or much higher than normal temperatures.
It's run pretty well the past two years, since I had to replace both fans. I suppose that may have contributed some wear. Yesterday's temp was hot (~95) but by no means out of the ordinary. Would there have been any wear to the switch itself during the few weeks that the fans didn't work, or is the blown switch just a symptom of pressure caused by an aging compressor or whatever?
 

dqa

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dbhyslop said:
I usually avoid Harbor Freight like the plague, but I couldn't turn down this price. When I took these out of the box they actually didn't look that bad. Typically you can tell a HF tool is going to fail just by looking at it. While I'm sure neither of these are up to the quality of the professional tools, they seem like they'll do for an occasional DIY'er.
If I want to replace the drier, will these tools do the trick, along with the drier, refrigerant, and some common sense? I don't have much experience working with the AC system, other than adding refrigerant and replacing the fans. But if it's not too complicated, I'd just as soon pay $100 for the tools and learn a little rather than pay $100 and have to interrupt my schedule.
 

dbhyslop

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I'm still new to AC systems, but it's become my opinion that this is something a consciencious amateur can do if they understand and respect how everything works and what the established procedures are. There are a lot of little gotchas--putting the right amount of oil in a replaced part, closing the system and applying vacuum within minutes of the dryer being installed, etc. Like any wrenching, mistakes can have consequences--expensive components can be damaged, or you could be killed or blinded by opening the discharge valve while refilling refrigerant.

Do a forum search, there's a few really good threads here about having the system open. I can think of two specifically in which the poster made mistakes. In one thread a guru went through point by point exlplaining what was done wrong and why. The other thread the poster thought he did everything right but the system didn't work afterward and he spent a ton of money to have it fixed.

There are forum sites out there devoted to automotive AC. Read everything you can find, but like anything realize that there's just as much misinformation out there and don't touch anything until you feel comfortable reading articles or posts and identifying what is good advice and what is BS.

Dan
 

BIGMIKE1.8T

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I have a 03 jetta 1.8t. i have no low fan speed. The a/c clutch does not kick on. I replaced the fcm with a used one no help. I also tested my old one on another jetta and found out it worked fine. all fues are good inlcuding the ones on the battery. the system is full checked 3 times. i got 27% duty cycle at the high pressure valve. have 9.2 volts at the compressor. 12 volts at the T14 (2,6,9) Have not check the fans by jumping yet. I know they come on at operating temp but not with key on and a/c on. Get 4ohms at the compressor coil at the plug when un hooked. I need help running out of ideas.

thanks
mike
 
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DanG144

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Mike,
Check the resistance of your ambient temperature switch, and ensure no mice have chewed through the wires.
Do you get the 9.2 volts at the coil when the coil is hooked up? You need some current load on the system while measuring that voltage.
 

jdross440

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Arkansas
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2002 Jetta
jdross440 said:
I checked mine and the drivers side was dead on low and high speed. Passenger side was good on low and high speed. Bought the Advance Auto assembly for $129 minus $20 (I had received an a coupon in the mail for $20 off on $100 or more that expired in 2 days). Now all is well.
Was under the hood today and turned the key to run and with the AC on low, only the passenger fan came on. Looks like the new fan assembly drivers side is aleady toast. As soon as I get my cast off my left hand, I'll unplu the drivers fan and jump to battery to make sure that's the problem. Good thing it has a lifetime warranty. Just a pain to change with full skid aluminum skid plate.
 

hotshot

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alabama
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2002 jetta
hey guys, i got fan trouble. anyone know if and where i could buy just the brush holder for the drivers side fan?? mine had a meltdown it seems. I think it got some dirt in it. anyway, i was wondering if i could just buy that part rather then the entire fan.

also, i was kinda using the fan repair tutorial when i realized that i did not have to grind off any tabs. you can also take a sharp chisel and give the tab one whack and it will bend back straight. once i did all the tabs, the back came right off.


just realized my car is not in my sig anymroe. 02 jetta tdi
 
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