Check your radiator/condenser fan operation NOW

[Jesterking]

So the next check is to see if there is voltage on the 4 pin heavy wire connector on the FCM, T4a/3 (supply from S180-30 amp for slow speed - which as you seem to know supplies the pin 2 of the radiator thermoswitch) and T4a/1 (supply from fuse S164-40 amp for fast speed).

It sounds as if you have a wire broken in there somewhere, it will help to know if the conductor is good to the FCM or not. There is a splice -k20- in the wire from S180-30 amp where it splits to go to the two places - FCM T4a/3 and Fan thermoswitch pin 2.

EXACTLY!!!

I unwrapped the wire bundle from thermo switch back towards the battery, and about 3 inches in front of the splice, it is corroded and broken completely through...now to complete a waterproof splice..

THANKS AGAIN!!

 

[GCBUG00]

Strike up the band!

 

[Jesterking]

EXACTLY!!!

I unwrapped the wire bundle from thermo switch back towards the battery, and about 3 inches in front of the splice, it is corroded and broken completely through...now to complete a waterproof splice..

THANKS AGAIN!!

Everything back together, I have AC!!! and both fans are operating!!!

THANK YOU DAN !!!

You saved me a couple of hundred dollars and countless hours of scratching my head!!!

 

[DanG144]

Good Job troubleshooting.

 

[tjsean0308]

Thank you.

Just want to say thank you to this community for saving me time and money. Thanks to the awesome info and circuit theory in this thread I was able to put a Fan Control Module in my car get my A/C back in the game.
I do have one question. What is the difference if any between these two FCMs?

The one on the bottom came out of my car the one on top was the one my local J/Y had and seems to be working correctly. It did come out of a car with the manual climate control. Couldn't really tell if it was a TDI or a gasser.

 

[DanG144]

I believe the only difference is the manufacturer. They are both series K. This does not necessarily mean they are identical in every respect internally, but that they both meet the form, fit and function requirements of VW.

 

[ngng]

I wanted to start by saying, thank you for all of the information!

My 1999 Mk4 Golf 2.0 has been having some issues with AC lately. Up until about a month ago the AC worked just fine. Then randomly it stopped working, generally. After driving for 15-30 minutes the AC would randomly kick on but the AC compressor made a horrible noise. The car has almost 240k miles, so I figured it was time to replace some parts. I started with the FCM, with a used eBay FCM but that didn't remedy the problem. I figured the compressor was dead, since it would kick on randomly. I replaced everything a few days ago and recharged the system at a local shop. After the system was tested and refilled the AC still did not work when I tried to turn it on. While driving home, 10-15 mins in, the AC kicked on randomly. I proceeded to dig in deeper and debug, but I'm stumped!

What I've done so far:
- replaced FCM with a used OEM unit off eBay (though I'm not sure my old FCM was even broken)
- replaced expansion valve, drier, and compressor; the compressor was a reman unit with a new refrigerant control valve, clutch, clutch coil, etc
- replaced AC pressure switch
- flushed the system with compressed air
- flushed the compressor with PAG oil and refilled with 5.0oz
- tested for leaks, put system under vacuum, and refilled with 750g of refrigerant

I've got through the "Mk IV Manual AC electrical & cooling fan troubleshooting and repair" mega thread. Here are the A4 fan troubleshooting tests I've run:

Fan response to Air Conditioner
The car failed when performing the first test:

Remember both fans should come on in slow speed any time the key is on and the AC
is on – if the temperature is above about 32 F (0 C). If one fan runs, so should the other
– they do not sequence on, or anything fancy...

Low refrigerant pressure will lock out both fans and the AC clutch.
High refrigerant pressure will put both fans in Fast speed.

I couldn't find any information what actually causes this failure. I need to double check the pressure, but I JUST had the system filled so I doubt that's the problem.

Next, I continued with some more tests, so I would have more comprehensive data:
- Verified S180 (fuse 8, 30 amps, green plastic, above battery) are OK
- Verified S164 (fuse 3, 40 amps, metal strip, above battery) are OK
- Verified 12V at all the connections and strips on top of the battery
- Verified fuses 5, 16, and 25 in cabin are OK and the FCM has power
- I removed the airbox/battery and checked for frayed wires or shorts and found nothing

Fan Response to Temperature Signals
- Verified slow speed fans from the radiator thermoswitch by shorting pin 1 to pin 2 with the key off; both fans ran at slow speed
- Verified high speed fans from the radiator thermoswitch by shorting pin 2 to pin 3 with the key on; both fans ran at slow speed
- Verified the resistance on both fans were within spec.

Am I missing something really simple? Thanks!

 

[DanG144]

You do need to keep on with the AC troubleshooting. The one for your car is not quite as developed as the later troubleshooting guide - I have just had less hands on experience. But you need to go through it. Can you verify that your car even has the same wiring as the 99.5?

It looks to me as if you either have a wiring issue or bad ambient temperature switch, or bad high temperature cutout switch.

 

[ngng]

You do need to keep on with the AC troubleshooting. The one for your car is not quite as developed as the later troubleshooting guide - I have just had less hands on experience. But you need to go through it. Can you verify that your car even has the same wiring as the 99.5?
It looks to me as if you either have a wiring issue or bad ambient temperature switch, or bad high temperature cutout switch.

When you say "later troubling shooting guide" can you point me to the guide you're talking about? So far, the wiring has been the same, so to the best my knowledge yes it's the same.

Is the ambient temp switch the same as the ambient temp sensor? The only reference material I can find says it's either behind the glovebox (www.vwpartscenter.net/volkswagen/go...-controls-scat/?part_name=ambient-temp-sensor) or next to the wiper motor in the engine bay. I've replaced the coolant temp sensor and I believe the high temp cutout (below the coolant temp sensor closer to the head) a few months ago, so I don't think they are faulty.

Also, would the failure of these two switch/sensors cause both fans to NOT run with the key on/AC on/fan on test?

Thanks!

 

[DanG144]

I am trying to decide if your system is the early one nominally from Sept 1998 through May 1999 (schematic #14) or the later one after May 1999 (schematic 38). The easiest way to tell is the early one has a high temperature cutout switch easily seen in a hard plastic fixture on the top radiator hose, out where it is easily seen. Supposedly you can tell by your build date, but I would not take that to the bank. What is your build date?

In either case the ambient low temperature switch or sensor (F38) will cause the loss of the compressor and fans. The high temperature cutout switch (F163) on the older ones will do the same. That is why I mentioned them as being suspect.

On the later system the high temperature cutout is done by the ECU communicating with the FCM, it cuts out the AC and turns on the fans for high temperature. The source of the temperature signal is from the CTS that feeds the ECU, by the head, driver's side, slid into the backside of the tee off the head. You can read this one from VCDS in the engine module.

You pick the right troubleshooting guide by choosing the proper PDF linked in the first post of this thread, depending upon your system.

The ambient temperature switch for the later systems is in the windshield wiper motor plenum, on the left side of the car. I cannot remember if it is the same for the earlier cars.

It would help me simplify my responses if I know for sure which system you have.

 

[tetragrahamaton]

Hey folks. My a/c system recently shut down completely. A/C button light does come on, but no clutch engagement and no fans running ever. Jumper on thermoswitch has no effect, but at least one of the fans does run when connected directly to battery. Today I found a clue: http://imgur.com/f0XP6mf

Any idea what might have caused this? Or is this likely the root cause; just a spontaneous failure of the fuse holder? The fuse itself appears to be unbroken.

 

[AnotherPerson]

Hey folks. My a/c system recently shut down completely. A/C button light does come on, but no clutch engagement and no fans running ever. Jumper on thermoswitch has no effect, but at least one of the fans does run when connected directly to battery. Today I found a clue: http://imgur.com/f0XP6mf
Any idea what might have caused this? Or is this likely the root cause; just a spontaneous failure of the fuse holder? The fuse itself appears to be unbroken.

That's the low speed fan fuse. One or both of your fans are going out and pulling way more power than it should. There was a design flaw with that box and the box usually melts before the fuse goes. When they start to seize up from age they pull more power.

 

[tetragrahamaton]

That's the low speed fan fuse. One or both of your fans are going out and pulling way more power than it should. There was a design flaw with that box and the box usually melts before the fuse goes. When they start to seize up from age they pull more power.

I see, so would testing the fan resistances be the best way to determine which one is failing?

Edit: And is it likely that there's also damage to the FCU?

 

[AnotherPerson]

You said one of your fans didnt run when connected to the battery. Safe to say that one is dead for sure.

If you havent ever changed any of the fans I would just order both of them and replace them both. Also fixmyvw.com has that fuse box on clearance for a VERY good price if they still have stock.

Im sending you a message in PM that you can get both bilstein fans from for cheaper than most places sell singles. Ive bought alot from them for my beetle and same for my sister with her 2001 jetta. All german quality parts. I just dont know how the rules are here for posting non sponsor vendors.

 

[tetragrahamaton]

Thanks! I actually only tested one of them, but I'm leaning towards replacing both as long as I'm digging around in there.

 

[AnotherPerson]

And don't buy auto parts store fans. Garbage you will be replacing very soon.

 

[Highlander_driver]

Hi Dan,
I have a 2004 Golf with manual a/c. Recently I noticed the a/c blows intermittently ambient at times. Other than that the a/c operation is normal. Ironically, my drivers side fan seized up and started smoking a few days ago. I have replaced both cooling fans now. I have done the fan test and noticed when I put the a/c on low (setting 1) the fans blow full power. I want to proceed with testing the hi & lo a/c pressures but can't seem to find the r134a gauges at local stores. Could you suggest what you think it maybe?

 

[AnotherPerson]

The hi/low switch kicks the compressor off. Also kicks the fans off. I don't believe your problem is with pressures. With the ac switch off do the fans still stay on full speed or turn off?


Sent from my iPhone using Tapatalk

 

[ngng]

I am trying to decide if your system is the early one nominally from Sept 1998 through May 1999 (schematic #14) or the later one after May 1999 (schematic 38). The easiest way to tell is the early one has a high temperature cutout switch easily seen in a hard plastic fixture on the top radiator hose, out where it is easily seen. Supposedly you can tell by your build date, but I would not take that to the bank. What is your build date?

In either case the ambient low temperature switch or sensor (F38) will cause the loss of the compressor and fans. The high temperature cutout switch (F163) on the older ones will do the same. That is why I mentioned them as being suspect.

On the later system the high temperature cutout is done by the ECU communicating with the FCM, it cuts out the AC and turns on the fans for high temperature. The source of the temperature signal is from the CTS that feeds the ECU, by the head, driver's side, slid into the backside of the tee off the head. You can read this one from VCDS in the engine module.

You pick the right troubleshooting guide by choosing the proper PDF linked in the first post of this thread, depending upon your system.

The ambient temperature switch for the later systems is in the windshield wiper motor plenum, on the left side of the car. I cannot remember if it is the same for the earlier cars.

It would help me simplify my responses if I know for sure which system you have.

Verified the build date off the door of April 1999. The high temp cutout switch is also present in hard plastic fixture in the top radiator hose (this switch is new).

 

[AnotherPerson]

Verified the build date off the door of April 1999. The high temp cutout switch is also present in hard plastic fixture in the top radiator hose (this switch is new).

Are you sure you have the correct switch? You should have a "blue" switch. Some of the after markets are considered "green" with blue plastic. No clue why vw did this. It's like the n75 valve connector change and all. Changed its shape but nothing else has changed.

 

[DanG144]

Hi Dan,
I have a 2004 Golf with manual a/c. Recently I noticed the a/c blows intermittently ambient at times. Other than that the a/c operation is normal. Ironically, my drivers side fan seized up and started smoking a few days ago. I have replaced both cooling fans now. I have done the fan test and noticed when I put the a/c on low (setting 1) the fans blow full power. I want to proceed with testing the hi & lo a/c pressures but can't seem to find the r134a gauges at local stores. Could you suggest what you think it maybe?

Your problem is possibly all driven from the issue with your cabin fan switch or wiring. That switch can sometimes be repaired, search for threads on it here. The switch assembly itself is pretty expensive, so folks straighten out copper strips and use epoxy to make a very decent repair.

That is where I would start. Once you have the cabin fans acting normally, then if your AC is still acting up, start on troubleshooting those circuits.

 

[DanG144]

Are you sure you have the correct switch? You should have a "blue" switch. Some of the after markets are considered "green" with blue plastic. No clue why vw did this. It's like the n75 valve connector change and all. Changed its shape but nothing else has changed.

ngng,
I suspect that AnotherPerson is talking about the CTS, coolant temperature sensors, just off the head, not the AC high temperature cutout switch that we are referring to in your early model MKIV.

So you have confirmed that it is the early model, and thus you troubleshoot it with the "Sept 98 - May 99 Build date A4 Manual Air Conditioner Troubleshooting "

My earlier statement was trying to point out that the guide (also a PDF linked in the first post of this thread) for the cars built a month after yours is much more detailed and thorough - simply because I could use my car as a guinea pig and test things out.

If you have not located and tested the F38 low temperature cutout switch (and it is an actual switch for your car, not a thermistor as on later cars) then that is where I would start.

Owners of cars built after April of 99, stop reading, don't jumper anything or you will cause damage.
Since yours is an actual switch, you can simply jumper around it for testing, once you find it. Or You can simply jumper from pin 2 of the F163 high temperature cutout switch to pin 2 of the four wire connector for your AC pressure switch. If your AC starts working when you do this, then it is the wiring, ambient temp switch, or high temp cutout switch. If this does not work, then verify that you are getting 12v at pin 2 of the pressure switch.

Be sure to refer to schematic 14, starting on page 97-152 of your Bentley manual.

Good job troubleshooting so far,

 

[Highlander_driver]

@Anotherperson, When I turn the fan switch off the fans do turn off.

 

[Highlander_driver]

This past winter I did repair the cabin blower fan (behind glove box) and the resistor. Not sure if that would have anything to do with it.

 

[ngng]

Are you sure you have the correct switch? You should have a "blue" switch. Some of the after markets are considered "green" with blue plastic. No clue why vw did this. It's like the n75 valve connector change and all. Changed its shape but nothing else has changed.

Just to ensure we're talking about the same part/location, what I replaced was #9 in the diagram:

I'll need to verify the color, but I believe it's blue; PN 059919501. I checked my order history and this is what I bought:
https://www.amazon.com/gp/product/B00DQCMAFC/

 

[tetragrahamaton]

You said one of your fans didnt run when connected to the battery. Safe to say that one is dead for sure.

If you havent ever changed any of the fans I would just order both of them and replace them both. Also fixmyvw.com has that fuse box on clearance for a VERY good price if they still have stock.

Im sending you a message in PM that you can get both bilstein fans from for cheaper than most places sell singles. Ive bought alot from them for my beetle and same for my sister with her 2001 jetta. All german quality parts. I just dont know how the rules are here for posting non sponsor vendors.

After reinserting that scorched fuse, the A/C system is working fine again, except that the fans seem to only run in high speed mode. I read that this can be caused by high system pressure, but the G65 duty cycle is at 26% with the system running and 22% with the system off, which I believe is on the low side.

The resistances of both fans match the "good" values in the fan troubleshooting guide pretty closely, so I'm feeling hesitant to replace them now. Is it likely that they're bad even though the resistances are normal?

 

[DanG144]

Yes, a G65 duty cycle of 22 or 26% is on the low side - VERY low side for operation in the summer.

Are the fans running continuously in the high speed mode, or cycling off and then to high speed and back to off?

 

[tetragrahamaton]

Continuously high as far as I can tell, any time the key is turned on or the engine is running. They switch off as soon as the key is removed, even if the engine is hot.

 

[ymz]

The compressor should spin very easily. It is basically doing no work, maybe 5 cc of pumping per revolution, and the pressure is the same on both sides, so all you should feel is the friction of the innards.

On our Silver car, that's the case... On our Black car, on which I'm replacing the coil, it's quite stiff... any guesses why?

Yuri

 

[DanG144]

if the compressor is stiff turning, then it may be that the oil was overheated in the past, when the fans were not working.

If it is stiff, it is probably not worth replacing the coil on, or at least plan to do a replacement soon. You probably need to flush it as well. If the oil is thick and black, or has metal flakes in it, you need to replace the condenser coils, the filter drier, the TCV, and flush the hoses and evaporator before installing a new compressor.