Fan/Ac issue

TDI4MI

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00 GOLF ALH 1.9 TDI MKIV
MK4 ALH 1.9...

So I was troubleshooting an AC issue. At first it was cycling - which I knew was not right (warm air). Then the compressor stopped all together. The lines show at least over 100 psi. So it has charge. The entire system was replaced a few years ago and worked great last summer. The next thing I realized the fans were not running! So at 190 - no driver or passenger side. No signs of overheating, even idling with it being 70 out today. I had a FCM handy new, and replaced. Still nothing. Unplugged the radiator temp switch, I jumpered the power (red wire) to the low speed terminal (red/white) and got low speed fan operation. I jumpered to the red/yellow wire and could not get high speed to turn on. I tried with both ignition key ON and OFF. So I confirmed the fuses are good, the fan motors are good and wiring. I do not think the water pump is an issue due to the fact that its A) not overheating or needle going past 190. and B) Both hoses are hot...upper and lower. I am running now to get a radiator temp switch - any ideas?
 
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J_dude

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SK Canada
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2003 1.9l “Jedi”
You've gone through this troubleshooting guide?
 

P2B

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I did. This pertains to fan operation at this point only.
The FCM uses a number of inputs to determine when the fans should run and at what speed. Those inputs are discussed in the diagnostic guide linked above, sounds like one of them is not what the FCM wants to see.
 

irvingj

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2005 Jetta Wagon TDI (PD/BEW)
Not sure of pressures with the new refrigerants, but 100 PSI doesn't seem high enough to me -- could that just be residual pressure in a system that's low on refrigerant?
 

oilhammer

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There are just too many to list....
I wouldn't expect an ALH to need its fans to come on at idle on a 70F day, none of mine do. And you've confirmed they can work.

I'd go back to your original problem... which was the A/C not working.

If the system has sufficient static charge, KOEO when you switch the A/C button ON, and the blower speed is not off, both fans should come on low speed. If they do not, either the system does not have enough charge OR the refrigerant pressure sensor is bad (or the signal from it to the fan control module is not right... broken wire, etc.).
 

TDI4MI

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00 GOLF ALH 1.9 TDI MKIV
I wouldn't expect an ALH to need its fans to come on at idle on a 70F day, none of mine do. And you've confirmed they can work.

I'd go back to your original problem... which was the A/C not working.

If the system has sufficient static charge, KOEO when you switch the A/C button ON, and the blower speed is not off, both fans should come on low speed. If they do not, either the system does not have enough charge OR the refrigerant pressure sensor is bad (or the signal from it to the fan control module is not right... broken wire, etc.).

I am stuck at getting the fans to come on during high speed op.

the low speed pin 1-2 works fine. The pin 2-3 with key on does not work. Which should be irrespective of the AC condition. I read 13.8v at battery, S164 and S180 fuse, and at pin 2. We know the motors on the fans work fine - in low mode. Tried another FCM - same condition. Just stumped.
 

oilhammer

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There are just too many to list....
You said in your first post you jumped both circuits of the thermoswitch in the radiator and got both fans to run both speeds:

MK4 ALH 1.9...

So I was troubleshooting an AC issue. At first it was cycling - which I knew was not right (warm air). Then the compressor stopped all together. The lines show at least over 100 psi. So it has charge. The entire system was replaced a few years ago and worked great last summer. The next thing I realized the fans were not running! So at 190 - no driver or passenger side. No signs of overheating, even idling with it being 70 out today. I had a FCM handy new, and replaced. Still nothing. Unplugged the radiator temp switch, and jumpered - through power on/off got low and high fans running both sides. So I confirmed the fuses are good, the fan motors are good and wiring. I do not think the water pump is an issue due to the fact that its A) not overheating or needle going past 190. and B) Both hoses are hot...upper and lower. I am running now to get a radiator temp switch - any ideas?
So which is it? They both work or one doesn't? Difficult to help troubleshoot if your information is unclear or changes.
 

TDI4MI

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00 GOLF ALH 1.9 TDI MKIV
Sorry, I mispoke on initial posting. Low speed works only (pin 1/2), not high speed (pin2/3). Could be still a bad FCM, but ha
 

TDI4MI

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00 GOLF ALH 1.9 TDI MKIV
You said in your first post you jumped both circuits of the thermoswitch in the radiator and got both fans to run both speeds:



So which is it? They both work or one doesn't? Difficult to help troubleshoot if your information is unclear or changes.
Sorry, I mispoke on initial posting. I jumpered the power (red wire) to the low speed terminal (red/white) and got low speed fan operation. I jumped to the red/yellow wire and could not get high speed to turn on. I tried with both ignition key ON and OFF. Could be still a bad FCM, but I did have a spare out of the box.
 

oilhammer

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OK, thanks for clarifying.

Have you tried jumping power to each fan's high speed leg directly to see if they run? The fan motors can lose one speed and not the other.
 

TDI4MI

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00 GOLF ALH 1.9 TDI MKIV
OK, thanks for clarifying.

Have you tried jumping power to each fan's high speed leg directly to see if they run? The fan motors can lose one speed and not the other.
I just did. Both fans run fine - pin 3 and pin 2 speeds are noticable.
 

oilhammer

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There are just too many to list....
I would go back and recheck all the stuff outlined in DanG's giude.

I'm a professional, and obviously have access to all the service literature and diagrams and what not, but even I refer to a printed copy of that guide because he did such a good and thorough job on what all the specifics are to check. I still use it to this day.

It may help to go at it from a couple angles, though, as your original complaint of no A/C clutch operation may not have anything to do directly with your fan operation.

I can tell you if your car came in here, my normal procedure is:

KOEO, turn the A/C on, verify both fans run on low speed. If yes, start the engine and see if the clutch engages. If no, find out why.

I'd also want to verify the system is full by weight, not just what a static gauge reads... although you can certainly put power/ground to the clutch connector to see if it works, and with the engine running see if the low side pulls down enough to make the low line feel cold to touch.
 

Zak99b5

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According to my research, which may be wrong, static pressure should be close to ambient degrees Fahrenheit. So if you got 100 psi on a 60 degree day, it's likely overcharged.
 

oilhammer

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Yes, that's about right... assuming the car was completely devoid of any heat. But if it has been running, even the latent heat from the engine will cause the static pressure to be up some over the ambient outside temperature. The compressor bolted to the engine, the condenser up against the radiator, etc. So 100 psi isn't out of the ballpark, really.
 

TDI4MI

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00 GOLF ALH 1.9 TDI MKIV
Always check wiring... I unraveled the tape on the T4 connector - seemingly wary of prior fix years ago by PO…and it seems that a bluish green corrosion or overheating of the line happened as it separated from the (red line). Furthermore there is some burning and intrusion or open on red/black cable. Figured 12v won’t be hitting that box…
 

oilhammer

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The T4 connector on the bracket above the starter? That's where the compressor clutch wiring goes through. That may be your problem right there, or at least one of them.
 

P2B

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That rings a bell...

 

TDI4MI

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That rings a bell...

Close…yours was reversed. I have good low power on pin 1 and 2, but not high on pin 2 and 3. Apparently, low will still work even though FCM doesn’t. Given that the power to the FCM was non existent - well this did it
 

lost1wing

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I had my pressure switch stick after replacing the condenser. The switch was on, neither fan would run and the compressor clutch would not engage. I put in about 12 oz but wouldn't take any more. One tap of the switch and the compressor clutch engaged and the fans turned on.

I also had a cheap aftermarket fcm not work out of the box.
 

lost1wing

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That's a really odd one, especially considering it's a pressure sensor not a switch.
I realized it wasn't a switch years ago when I tried to jump it to get to compressor on. Either way could have been a bad terminal connection in the switch (sensor) or an oxidized contact that needed a little help. I had another issue with the expansion valve. Twenty five year old cars need a little tlc to wake them up sometimes.
 

oilhammer

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There are just too many to list....
We had some DIYr clown fry a $2k HVAC controller on a Ford Fusion once trying to "jump" a refrigerant pressure sensor, LOL.... good times... :D
 

TDI4MI

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Well, that was it - the red power 12v cable was detached from the FCM and heavily oxidized, probably from overheating at some point in the fuse block. Prob some PO rigged it. Then there was burning and damage to one red/black and sheath damage to another. I cut in some new cabling, and wallah! Pins 2 and 3 work. May have also gotten AC back (will have to wait until its warm out to really check) - as my compressor comes on with both fans and solid light.

I assume my AC and fans worked due to the wires maintaining a limited connection - and then it finally detached at one point, so this was a tough one. Considering I would have had to tap into the wires to check continuity from the FCM - which I was almost about to do.

Moral of the story - check your wiring people. Never know what's going on underneath the wraps.
 

P2B

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Considering I would have had to tap into the wires to check continuity from the FCM - which I was almost about to do.

Moral of the story - check your wiring people. Never know what's going on underneath the wraps.
I found my issue in the same spot by poking a pin through the insulation to check continuity.
 

lost1wing

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We had some DIYr clown fry a $2k HVAC controller on a Ford Fusion once trying to "jump" a refrigerant pressure sensor, LOL.... good times... :D
I never had that misfortune, but it is a good idea to know what you are doing before you start playing with electrical stuff.
 
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