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chrisbwy

GTI - Air Con not working

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Hi All,

I've searched on here and lots of other VW forums for advice on why my Air Con no longer engauges the compresssor pump. Radiator fan doesn't come on either. The A/C switch does light up. (not sure if the rad fan comes on when engine hot, I need to check that out too)

VW garage read fault codes and replaced the gas low pressure switch, but still not working.

System has been re-gased and is holding pressure.

Golf MK4 forums speak of a fuse 16 that feeds the Fan Control Unit "1J0 919 506 K" located just behind the n/s headlight.

Any ideas which fuse this is in the Lupo GTI?

I've checked the small fuse box in the engine bay (near washer bottle) - all ok.

I suspect at the moment the FCU is faulty/corroded.

What's the best way to get at this unit? From the top or bottom? And is there enough slack on the loom to remove it from its mounting bracket to get at the terminals easier?

Unless you have other ideas why the A/C isn't engauging.

Thanks all,

Chris

 

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I have the same problem with mine.

Compressor was changed and engages when the button is pressed. System holds pressure and the light comes on, but no cold air. Rad fan doesn't run.

I changed the relay you are talking about too. Its under behind the NS head lamp, but is easier to remove the wheel arch liner and get at it that way.

:-(

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Main VW dealer only found low air pressure switch fail code, replaced switch but still no clutch pull in on compressor.

Next is to look at fan relay module.

 

inide - i'll do as you suggest and get in through wheel arch, removing liner. Did you get yours working again?

 

Regards

 

Chris

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Sorry for the delayed reply.

Sadly not, mine is still not functional :-/

I've not changed the switch in my case. Do you know if that is something that can be done without dropping the refrigerant gas etc.

Do we know if the radiator fan is supposed to run when the air con is switched on? Mine definitely isn't doing that.

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The VW dealer definitely had to re-gas after changing the pressure switch. They wouldn't look at any other cause for the system not working until they'd changed the switch and removed the fault code. So they did the switch change, it removed the fault code but sadly still no clutch engaugement.

My system is holding gas pressure ok - they confirmed that.

My next job is to look at the fan control module - I want to double check the rad fan runs if the engine gets too hot, since I understand this module controls that as well as running the fan if the A/C is enabled. This module also engauges the A/C compressor clutch - which is not happening on my car.

Does your A/C compressor clutch engauge? Did it do that before you changed the fan control module?

Thanks

Chris

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My story is a little boring, but I'll give you the gory details ^_^

Ended up being seriously f*cked around by Volksline (Broadoak road) in Canterbury (horrific customer service and I don't mind publicly saying that) - they have a bit of a rep for it.

The car went in for a simple aircon recharge, but I was told the compressor had packed up and was definitely the cause. Of course 500 quid later, still no cold air. Couldn't get a straight answer if the part had actually been changed, wasn't allowed my old unit back. I suppose I trusted them to solve the issue because they are a VW specialists and the system had been working perfectly until the end of that summer.

As a next step they said that the fan control module might need changing, but I declined their extortionate (£300) offer to replace the part.

The situation was all the more frustrating because I'm handy with spanners, but aware that air conditioning is not all that easy to work on at home.

Unfortunately after also changing the fan module the air conditioning remains in a none functional state, which is really frustrating. Double checked I had the right part as well.

All I can tell you is that my compressor does indeed engage and the rad definitely runs when the car gets warm in traffic.

Beyond this I lost interest in solving the problem as it had frankly cost far too much already!

So I suppose the next step would be to try the switch, although I'm sure that'll come at some significant cost too.

Out of interest what fault code did yours throw up? I assume the EML didn't come on, this was just visible when using the VAGCOM system.

Edited by indie

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I share your pain but not yet your cost! Sorry to hear that.

I can't recall the specific VW fault code for low pressure switch fault, but that's what they said it was and went ahead to drain, change switch and re-fill gas. No EML on. I would assume that a faulty switch would act like being in low pressure and stop the compressor from being enabled in the first place. Yours does enable so I doubt the low pressure switch is faulty. Also surely Volksline would have checked the A/C system on your using VAGCOM first.

Your system is performing "better" than mine, in that you do have clutch engaugement and rad fan running when you press the A/C switch - if I understand your notes correctly. If your system is full of gas then how come it's not cold? Don't undetstand that, particularly after a new compressor. Any ideas?

Did changing the fan control relay make any difference to the system?

Where did you get the replacement from and what part number?

I'm making space in the garage for the car to try and diagnose further so will update this thread with any news - it could be weeks, but I will report back.

Interesting reading...

http://www.gti-vr6.net/wiki/index.php?title=Fault_diagnosis_in_the_Fan_Control_Module

Hopefully we might be able to give each other clues!

Best of luck.

Thanks

Chris

Edited by chrisbwy

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I had the exact same problem on a mk4. My first step was to prove the system still physically functioned. I made up a lead so I could power the compressor solenoid, using an old fuel injector cap (they have the same plug). With the engine idling, I powered the compressor for max 30 seconds which duly clicked in and then started running. Inside I had the fan on plain fresh air and simply felt the air being blown out of the vents. Yup, icy cold, which told me the system did indeed work just fine. So it was an electrical problem.

If you try this, don't run it for too long as the system can over pressurise. There is a dump valve on the back of the compressor which will vent refridgerant if the pressure goes too high to save blowing any pipes or downstream components.

Vagcom messages were all useless.

Everything else on the car worked just fine.

So it had to be the fan control relay thing. Regular engine cooling fan control worked ok; no engine overheating or anything.

Bought a used, 'working' unit and tried that. No change. Hmmmm.

Might be the over/under pressure switch, or connection. So unclip and measure the output. All fine. I've never ever seen one of these fail.

At this point I started to think the same as previous posters. I read the other forums about the fuse near the battery connection, but it was just fine. That lead me to think that if just one fuse can give rise to all those symptoms, it could be a +12V supply problem from the fuse to the fan relay thing.

Found it...! There is a little plug that has wires hanging down vertically from the battery mounted fuse pack. In non ac cars, it has just one wire which I think is for the radio. On ac cars there is a fat wire which is for the ac.

Somehow when working on the car I must have bumped it and the plug was not fully clicked in. I clicked it back in and sure enough, the ac started working again. :)

 

 

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On 11/08/2016 at 10:37 AM, chrisbwy said:

The VW dealer definitely had to re-gas after changing the pressure switch.

That's rubbish. There's a shut off valve in the pipe. When you unscrew the switch, the valve in the pipe shuts off the gas. It's like a car tyre valve. You might get a little "ptssss" sound for a second, but not enough gas escapes to need a regas.

Reading this just makes me mad at those stealership mechanics.

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On 8/11/2016 at 3:46 PM, indie said:

All I can tell you is that my compressor does indeed engage and the rad definitely runs when the car gets warm in traffic.

Mine was doing the same.

VAGCOM threw up a code for the pressure switch, but changing it didn't solve the thing. I have a friend who works for an aircon company (industrial) and offered to lend me a hand checking what could be wrong with mine. Turns out it was the compressor, which engaged but didn't seem to compress.

We fit a used compressor, recharged the gas and it's working perfectly now :)

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Thanks mk2 for your comprehensive comments. I will check the lead/connector you mention.

Dealer didn't charge me for the new presure switch nor supposed re-gas. But I am loosing confidence in this main dealer now.

I need engineers who diagnose and fix - not technicians who just read fault codes and change parts, fingers crossed.

If I find anything I'll update you all.

Regards

Chris

 

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