Check your radiator/condenser fan operation NOW

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MKIV_TDI

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2002 Jetta TDI, 2002 Golf TDI, '89 Audi 200 Wagon Quattro 2.5 AEL TDI
MKIV_TDI said:
My poor aunt just bought a 'new to her' 2002 NB with 160k miles and just as she was pulling into my driveway to show me her new car, the serpentine belt snapped!
In fact, she almost hit my mailbox because she lost power steering!
After a quick peek underneath, I looked at all the pulleys. Long story short, the AC pulley was totally seized. It took two hands and a tremendous amount of force to make it spin.
I removed the AC unit and it was some Chinese knockoff POS that the previous owner installed, and I was fortunate enough to have a genuine known working one one in my garage off of an engine with 100K miles.
After sending her to a garage to swap her condensers and refill, there's still no COLD air. Just barely "cool".
Then I came across this thread and I did the "AC On + Fan On + Ignition" test, and neither of the radiator fans are spinning.
I'm going to try and follow these steps to try and pinpoint her issue.
The fuses on top of the battery look great. No sign of damage/corrosion/melting. Her fuse #15 (red 10a) was burnt.
I'm going away this weekend, so hopefully it doesn't make anything worse till I can take it all apart...
Click to expand...


Following up! So I cleaned both fans, and all speeds are up and running.
But still, there's got to be something with the compressor itself?

I can put my hand on the AC pipe and it's not cold.

My '03 TDI's pipe is ICE COLD to the touch after about 20 seconds of running, by comparison.

Not sure where to go from here...
 
dremd

dremd

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06 sprinter. 03 jetta wagon premium with 6 speed ALH swap, 14 JSW
Sounds like you need to change the RCV in the compressor. (Refrigerant Control Valve).
 
B

Brkbeatsci

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DanG144 said:
It is ok to unplug the compressor, typically. The FCM will sense an improper resistance on the compressor line, and stop feeding power down the line. It may still have leakage current which will produce a voltage, if it is only loaded by a high impedance voltmeter.

I would look really hard at your main power supply fuses, and ensure that they are providing power without too much voltage drop when fully loaded.

I would also do a good visual check on your T14 wiring, for corrosion on the back and internally.

Good luck.
Click to expand...

Update.

I left the new pressure transducer in there, reinforced the ground to the t14 harmess and replaced the fan control again with a brand new streibel (sp?) Unit. The fans came on low no problem but the compressor still didn't engage. After further checks I found that during my testing I must have pushed the female receptors in the two pin clutch harness far enough apart that they weren't engaging the male pins. I adjusted them back closer together and everything is firing up normally.

DanG...thanks so much for putting this thread together and for your quick replies. It saved me a ton of money. Next time you're in Philadelphia there's a cheese steak and s beer waiting for you.
 
M

MKIV_TDI

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Location
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2002 Jetta TDI, 2002 Golf TDI, '89 Audi 200 Wagon Quattro 2.5 AEL TDI
Question -- when removing an old compressor, black "ooze" dripped out of one of the lines and started bubbling. About a teaspoon's worth. Any idea as to what that may say about the integrity of the system?

In a previous post I had mentioned that the old knockoff A/C had seized up and wouldn't spin by hand unless you really manhandled it. Could it have contaminated the system and sent garbage everywhere?
 
A

AnotherPerson

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1999 Beetle
MKIV_TDI said:
Question -- when removing an old compressor, black "ooze" dripped out of one of the lines and started bubbling. About a teaspoon's worth. Any idea as to what that may say about the integrity of the system?

In a previous post I had mentioned that the old knockoff A/C had seized up and wouldn't spin by hand unless you really manhandled it. Could it have contaminated the system and sent garbage everywhere?
Click to expand...


There is flush products that can clean out the system. After you use them most of the time you have to add oil to the system though. Also remember to always change the dryer.
 
D

DanG144

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Chapin, South Carolina, USA
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2005 A4 Jetta 5spd
Yes, black ooze is know to AC professionals as "the black death". It means a complete flush of the system, new compressor, new filter drier at a minimum. It means gross overheating or aluminum particle oxidation due to oxygen ingress or both.

A pro would almost insist on a new condenser because it is almost impossible to flush it properly.

A new TCV may be in order as well.

This is about the worst news you can get on an AC system.
 
Sooch

Sooch

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Des Moines, IA
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2005 Golf
Hey Dan,
Been a long time since I posted!

My AC is on the blink in my 2005 Golf TDI. As hard as I look, I can't find an AC clutch relay. The reason I am looking is because I have checked the pressures, the fans work right, the AC clutch is engaging and it sorta of works. The compressor cuts in and out at anything over idle rpms. It is behaving exactly like the 2005 Passats with the relay 384 issue...but I don't have one of those.

Can you tell me where this elusive relay would be? Or do I have a sensor issue?
 
D

DanG144

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2005 A4 Jetta 5spd
You may be having an HP sensor issue.
The system will shut off the compressor if it THINKS it has high pressure (or low), sometimes these sensors start failing with a sawtooth type waveform- ramp up from low to high, drop and start over. "Low" for the ramp can be any pressure from zero to 500 psi.

It can also be a heat induced open circuit of your clutch coil, but the fact that it happens with high rams suggests a bad HP sensor.

To really tell for sure, you need to put a set of gauges on it and compare the duty cycle output from the HP sensor to the actual pressure.

The details are in the PDFs in the first post.
 
V

vti-chris

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Golf IV
Hi guys problem with fans here as well. I have a golf TDi 2000 model. A few months ago my michanic noticed that the big radiator fan was not working and suggested replacing. After following the repair thread from the forum i managed to fix the fan motor and while it was a bit noisy it seemed to work fine. The summer has kicked in now and i used the A/C. When the car is traveling at low speeds the air is just below ambient temp...when i pick up speed the air is close to normal as it used to. I then checked the fans and none of them works. I first checked the fuse above the battery but that didn't cut it although i here a click whenever i insert the fuse back in.
Car temp did't rise at all even on heavy traffic and this was weird?
Any guidelines on where and how to check/fix this??
 
A

AnotherPerson

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Noisy fan means it was dying. Pulling more amps than it should have. It's time to replace them now. The clicking is a good sign tho as it means your fan control module is still working and didn't melt.
 
V

vti-chris

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If i remove the fans and use a small Lipo 11.1v that i have to confirm if they work would it be safe or it will spin very fast and risk injury??
 
A

AnotherPerson

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There is a procedure listed at the beginning of this post how to jump out the sensors and turn the fans on. I wouldn't power them up off the car myself. It's not hard to jump them out on the car. But you said the big fan was making noise. That means it was going out way back than.
 
D

DanG144

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2005 A4 Jetta 5spd
Any 14.5 volt DC source or less is safe to power the fans (in the MK IV), even reverse polarity does not hurt them.

By doing it in the car you can also check voltage drop from the fuses and circuitry, which is often a problem in these cars. But I check my repairs using a spare battery in the shop.
 
A

AnotherPerson

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DanG144 said:
Any 14.5 volt DC source or less is safe to power the fans (in the MK IV), even reverse polarity does not hurt them.

By doing it in the car you can also check voltage drop from the fuses and circuitry, which is often a problem in these cars. But I check my repairs using a spare battery in the shop.
Click to expand...

I have a voltage drop to 11.7v off and around 13.7v when on. Is this OK?

Exiting the fuses I have battery voltage or 0.1v less. Its dropping somewhere else.
 
C

CrustyOreo

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Hanover, Mass
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2011 Golf 2 Door 6MT
Troubleshooting a/c here quick question:
I turn the a/c button on with key ON and only the fan on the driver's side comes on. Is it possible that the second fan has gone bad? I assume the FCM sends the same signal to turn both on
 
A

AnotherPerson

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CrustyOreo said:
Troubleshooting a/c here quick question:
I turn the a/c button on with key ON and only the fan on the driver's side comes on. Is it possible that the second fan has gone bad? I assume the FCM sends the same signal to turn both on
Click to expand...


Correct. Sounds like low speed is bad on that one. Double check that fans connector also. You never know if road debris could have gotten to it somehow
 
C

CrustyOreo

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I'll take a look.
This a/c system has been giving me grief for a couple years. Had it vacuumed and recharged 2 days ago. Nothing from the compressor. Yesterday the compressor turned on and I had cold air for about 15 minutes. Then nothing. Then today I had cold air for around 15 minutes again
 
C

CrustyOreo

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DanG144 said:
Definitely check out your wiring. Look for hot spots, corroded spots. Look down in the fuse base on top of the battery.

Intermittent issues are most often electrical.
Click to expand...
Fuse panel has seen better days but I checked the fuse receptacles and they were clean. Will check wiring,.

AnotherPerson said:
Sporadic ac operation can also be caused by the pressure switch. Mine wouldn't always turn on at car start so I replaced it.
Click to expand...
Is this the one right in front of the firewall? I have the old 4 pin style. Is there a way to jump it?
 
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D

DanG144

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AnotherPerson said:
I have a voltage drop to 11.7v off and around 13.7v when on. Is this OK?
Exiting the fuses I have battery voltage or 0.1v less. Its dropping somewhere else.
Click to expand...
While 11.7 volts is enough to run the fans, you are losing 2 volts - a 15% voltage drop. Power is equal to current times voltage. Power is 2 volts x 20 amps (two fans in slow speed or more in fast speed), you are losing 40 watts of power somewhere along the way. Ever tried to put your hand on a 40 watt bulb? Something somewhere is getting pretty hot.

Was the 2 volt drop in slow or fast speed?
 
A

AnotherPerson

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DanG144 said:
While 11.7 volts is enough to run the fans, you are losing 2 volts - a 15% voltage drop. Power is equal to current times voltage. Power is 2 volts x 20 amps (two fans in slow speed or more in fast speed), you are losing 40 watts of power somewhere along the way. Ever tried to put your hand on a 40 watt bulb? Something somewhere is getting pretty hot.
Was the 2 volt drop in slow or fast speed?
Click to expand...

1v drop. 11.7 was engine off. 12.7 at battery when tested.
 
D

DanG144

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CrustyOreo said:
Welp I think my problem was the a/c clutch. It's now making some bad noises!
Click to expand...
Ensure it is the clutch and not the carrier bearing.

If it is the clutch it will stop making noise when you turn the AC off. If it is the carrier bearing it will not.

When the carrier bearing fails, it quickly gets to the point that it gets hot enough to cause a fire, and burn your serpentine belt. It can also just cause it to break.
 
B

BettyWhite

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Detroit
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2003 Jetta GLS
New to the forum and I just started troubleshooting my VW's fan operation. I wanted to share some observations while I dig through this thorough thread.

The AC doesn't operate at any of the fan speed settings. Driver side fan is non-operational regardless of if the manual AC button is engaged or disengaged. At key on, the passenger side fan kicks on (I'm not sure if it's low or high speed operation yet). At key off, the passenger side fan stays on for 5 minutes (again, I'm not sure if this is low or high speed operation yet). Thanks in advance for anyone's help.
 
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A

AnotherPerson

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BettyWhite said:
New to the forum and I just started troubleshooting my VW's fan operation. I wanted to share some observations while I dig through this thorough thread.



The AC doesn't operate at any of the fan speed settings. Driver side fan is non-operational regardless of if the manual AC button is engaged or disengaged. At key on, the passenger side fan kicks on (I'm not sure if it's low or high speed operation yet). At key off, the passenger side fan stays on for 5 minutes (again, I'm not sure if this is low or high speed operation yet). Thanks in advance for anyone's help.
Click to expand...


I would say bad wires or fan on the drivers side. Leaning towards a bad fan. When the engine is cool with the air turned off does key on make the fan come on right away?
 
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