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Guide to A/C system and faults .

I can't believe I missed this post. Mine started doing this whining noise last year, turn off AC and it stops. Been driving me mad. Thanks Demort!
 
@ NedHan79

Its a bit fiddly shall we say .. the rear bolt is accessed down through the inlet manifold , i think you remove the engine bay temp sensor and get at it that way ... i'm afraid i just do it and dont think about which bits i remove .

A wobbly type extension of about 4 inches and a 13mm socket .. when undone its a case of holding it up to get the compressor forward .. either fingers or a telescopic magnet .

Under this bolt and with the compressor out you will see a spacer .. its just pushed into the hole .. don't loose this or knock it out as it has to be there when refitting .

You don't undo the pipe at that allen key .. follow the pipe to the o/s/r and above the main wiring plugs .. disconnect it there .

video for you ..

https://www.youtube.com/watch?v=-5YrhwxPgMs

@ JTT
Check condensers for leaks and the rear pipes .. if nothing obvious then just get it regassed .. they do loose gas over time so its not always a leak .
 
Good helpful post!!

I have an issue with the AC in my car. It was re-gassed last year after i repaired a leak. It now gets down to temperature and is fine for a period of time (say 3hrs) but after then, it stops running cold and warms up.

The next time i drive the car, its cold again.

Any ideas on issues?
 
I've got a couple of hunches here ..

Down side .. the only chance you have of proving them is with a tester that can see the actual values of the sensors and you need to be looking at it when the fault is there .. in other words the a/c doesn't seem to be working .

First one .. a/c pressure sensor , fitted next to the dryer .. im wondering if over a period of time its seeing an over pressure and shutting down .. may be a sensor fault or an actual fault due to a restriction .. cant say .

Second would be an interior temp sensor is faulty .. if the sensor incorrectly reads then the a/c thinks the car is at 4 degrees for example when its actually 18 .. a/c will act on what the sensor says so will shut down a/c until it sees this sensor read higher than the specified temp .

I think .. if the fault happens .. switch it to Low temp and see if the a/c kicks back in again .. if it doesn't i would lean towards my first answer .
 
I have a general question about the AC. I guess this is as good a place to ask it....

What temperature should the air be (at the vents) when it's on low? I realise that a 996 isn't going to be as great at chilling the car as a more modern vehicle, but my AC doesn't seem that cold.

I could measure the temp with a meat thermometer in the vent, but I don't know what to expect as a reasonable temperature.
 
Mine feels pretty cold, if it doesn't you may need a re-gas?
 
heed said:
I have a general question about the AC. I guess this is as good a place to ask it....

What temperature should the air be (at the vents) when it's on low? I realise that a 996 isn't going to be as great at chilling the car as a more modern vehicle, but my AC doesn't seem that cold.

I could measure the temp with a meat thermometer in the vent, but I don't know what to expect as a reasonable temperature.

You would be looking in the region of 6 degrees Celsius .

Rule of thumb .. measure with a/c off and on low setting then the same with a/c on ...

Compare the difference between the 2 .
 
So, the plot thickens....

This is current situation:

LO, max power, no AC (no frost flake), running engine (car warm) temp is ~19C.

Same settings but press the snow flake: temp stays the same. No change at all - 19C.

No noise at all when pressing snowflake, though the AC condensers do come on at front of car.

OK, so I go to Halfords for a "free check"; I just wanted to see if there was anything in the system. Chap has one of those cans with the PSI gauge on it. Not a good start. Anyway, he puts it on and the pressure is low/none existent.

So I'm thinking leak or it never got refreshed after some work...

I explain it needs 900g along with the correct oil but he's like "er this is PSI and has coloured regions on the dial". We figure it's worth putting some in to see if it holds. At least I'll know if there is a gaping leak anywhere.

So he fills it so it's in the green zone. I believe somewhere between 25-40 PSI . (it was about 17C today).

With the car running and AC on the pressure seems to hold in that zone but still no AC.... Temp at vents doesn't change...

He doesn't charge me (I should hope not!) and I ***** off.

On drive back when I have the AC on it now produces a very strange noise...

https://youtu.be/ylLLgnCUfow

It's coming from very near the refill valves and battery in the frunk. It comes on when AC is activated and stops when AC turned off. The fan speed does not affect the noise.

This is the history:


  • - 2012 AC condensers replaced
    - 2018 TVR101 did an AC service. I rang them today and they confirmed that they drained and refilled system. No problems

What should be my next steps?


  • - What's that noise!? Is it because there is a non-zero but not enough amount of gas in the system?
    - I have an Autel 805. It has a lot of 996 info. Is there anything I can check that would help identify an issue? It has live reporting too if there is a test I could do with the AC on/off?
    - Should I take it to somewhere with a proper machine and get it gassed?
    - Should I just wait a week and take it to see if all the gas has gone?
    - Should I check the compressor?

The fact there is no gas says to me that there was a leak, but that doesn't explain why the system didn't work when it was gassed and under pressure?
 
I listened to about 5 seconds of that video .. its low a/c gass basically .

Regassing via pressure gauges is pretty old school .. its that old i've never learnt it !

the car needs to have 900 grams of gas put in the system .. modern machines do a leak check .. if that fails then there is an obvious leak but it won't detect a small leak.

In other words you regas a system and it makes that noise or stops working in 3 months .. that's a slow leak .

You can have other faults ..

IE .. if the car sees the interior temp as 10 degrees .. faulty sensor then it will shut down the a/c as it thinks the car is already cold .. it may even start blowing hot air to get to then temp you have selected .. say 18 .

For me and the first thing is to make sure you have the correct amount of gas in the system ... so get it regassed and go from there .
 
To add to this thread, I have a slight clicking noise coming from under the passenger side of the dash that changes with the speed of the fan setting on the climate control.

I think it could be the fan under the pollen filter, I'm going to take a look and see if something is catching but wondered if there was something common I'm missing first?
 
pop the pollen filter out and have a look at the fan for leaves .. nuts .. mice debris .. i've seen various things in there before thanks to our furry friends .

Spin the fan by hand .

This on a 997 / 987 would be a flap motor sticking and not reaching its end stop .
 
Will check it out tomorrow and report back, thanks.
 
A thin section of the insulation on the recirc flap had come off and was catching on the fan - now removed and normal service resumed. :thumb:
 

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