Very Frustrating aircon problem that specialists have tried

[X-UFO]

As per the title: very frustrating aircon problem that a few specialists can't resolve

Here's the story.

2001 996 3.4 C2

The aircon initially wasn't working when I drove the car 5 weeks ago. Garage said it would be fixed. Two days later regassed

it and it worked fine.

I picked it up a week later (4 weeks ago) and it was working but had a droning, bearing type noise mainly on tickover and up to 1,200rpm

with the noise changing slighlty with engine revs. Since, I have noted that it is noisier when the weather is warmer outside. However the aircon always works

well and is cold enough. The noise seems to be coming from the front of the car around the bulkhead area but listening to the metal pipes it can be heard more. It sounds worse inside the car than on the outside.

Spoke to dealer who gave me a letter saying that he would pay for any problems with aircon for next three months in case it was leaking gas etc.

So, next day, called a specialist aircon person who came out regassed the system (again), changed the expansion valve and gave the system a thorough checking over and put gye in. He reckoned the compressor was fine. The noise seemed to be better but not completely gone. Next day was a very hot day and the noise was worse than ever.

A week later the specialist came out and checked the gas level, pressure etc etc and couldn't find any leaks and couldn't imagone what was wrong unless it was vibration in the pipes. He noted that the compressor seemed to be on all the time when the aircon was on and didn't seem to switch in and out. However, the pressure in the system went up and then down as it should (seemed regulated). Didn't seem to be any leaks but the fan wasn't working on one of the front rads/condensor.

A week later I took it to an independant Porsche Ferrari specialist who spent 4 hours investigating and rang some aircon experts they use who basically said they hadn't heard anything like it before. So, 4 hours labour was charged and the fault is still there.

The series resistor has been changed on one of the fans and it now works along with the other fan when the aircon is on.

Still this fault is there and on a hot day it's really annoying. It has cost £200 initially for the expansion valve and regass. Then £200 for investigation that didn't deduce anything and another £250 for the series resistor change. Total so far £650 and the only difference is the fan now works.

If anyone has had a similar experience I really would appreciate any pointers.

Thanks in advance.

Edited August 29, 2008 by X-UFO

[PTEC]

So has anyone actually replaced any parts/seals or do they just keep recharging it? Does the noise occur when the ac is off?

Edited August 30, 2008 by PTEC

[X-UFO]

So has anyone actually replaced any parts/seals or do they just keep recharging it? Does the noise occur when the ac is off?

The noise starts as soon as the aircon button on the dash is pressed. Seems to be coming from behind the dash or on the other side of the bulkhead.

The noise stops as soon as the aircon is switched off on the dash.

Only thing changed so far is the expansion valve.

Compressor clicks in and you can see the clutch on it operate but seems not noisy at all in engine bay. Howver, it does seem to be working all the time

not kicking in and out. Would be interesting to know if others compressor kicks in and out on it's own or whether constantly engaged like mine.

[X-UFO]

Edited post.

Edited August 30, 2008 by X-UFO

[wwest]

Pressure going up and down as if regulated but compressor clutch always engaged seems improbable. Some newer systems use a variable displacement compressor so the clutch, if any, is always engaged. But I don't think the '01 used that system.

A good test would be to disconnect the A/C clutch electrical connection at the compressor and see if the sound changes.

You may have a defective refrigerant pressure switch which doesn't turn off the compressor when it should, that would certainly result in some very strange noises as the liquid refrigernat reaches the compressor intake.

[wvicary]

Does the noise change when the cabin fan changes speed at all?

[KevinMac]

Does the noise change when the cabin fan changes speed at all?

Check the dryer. Run the Ac and pull the plastice cowl/battery covers off and see if you can hear the noise.

Edited September 3, 2008 by KevinMac

[X-UFO]

Does the noise change when the cabin fan changes speed at all?

Check the dryer. Run the Ac and pull the plastice cowl/battery covers off and see if you can hear the noise.

Thanks to both for the replies. After taking it to a proper specialist he diagnosed it within minutes. It's a leak in the pipework going up the rear

arch to the compressor.

It seems the leak causes the vibration to travel through the pipes and the noise appears to be from the front of the car.

Just goes to show that the first so called ripoff 'specialists' don't know what they are doing and wasted 4 hours not looking further than watching time clock up in labour per hour.

Then after clocking some time up they gave it back and charged for telling me they didn't know what was wrong with it.

I need to book it in and get it done.

When this is sorted I'll post on here a new thread praising the new proper 'specialist' who knows porsche inside out. Credit where credit is due.

Thanks to those who replied to this thread.

[KevinMac]

Does the noise change when the cabin fan changes speed at all?

Check the dryer. Run the Ac and pull the plastice cowl/battery covers off and see if you can hear the noise.

Thanks to both for the replies. After taking it to a proper specialist he diagnosed it within minutes. It's a leak in the pipework going up the rear

arch to the compressor.

It seems the leak causes the vibration to travel through the pipes and the noise appears to be from the front of the car.

Just goes to show that the first so called ripoff 'specialists' don't know what they are doing and wasted 4 hours not looking further than watching time clock up in labour per hour.

Then after clocking some time up they gave it back and charged for telling me they didn't know what was wrong with it.

I need to book it in and get it done.

When this is sorted I'll post on here a new thread praising the new proper 'specialist' who knows porsche inside out. Credit where credit is due.

Thanks to those who replied to this thread.

Great good news!

[X-UFO]

Great good news!

Thanks matey :D :D :D

Edited September 3, 2008 by X-UFO