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deMort
Long Beach


Joined: 21 Mar 2015
Posts: 6155
Location: Brighton


PostPosted: Sat Feb 23, 2019 7:43 pm    Post subject: Guide to A/C system and faults . Reply with quote

If your car is making a whineing noise .. a rumble .. a noise like a worn bearing then try switching off the a/c .

If the noise goes then the fault is probably low a/c gass .

To test your car i find a temp of 19.5 with a fan speed of 3 .. give it a few mins on idle .. if you then hear a noise that stops when you switch off the a/c then its low gass .

A/c gass .. which on these cars is R134a will have an annual loss of 10% per year .. you dont have a leak as such but its the normal escape of gass from the system.

If your car hasent been regassed in several years then you can see it is already low and you have probably gotten used to any noises .

Leak areas .. obviously it can leak from any part of the system but the main 2 places are the front condensors and the o/s/r pipe connections .. just im front of the o/s/r wheel and under the panel .

Condensors and you have to replace them .. see the image below for " damp spots " these are small leaks and will have an oilly / dirty look to them .. if you are lucky you will see sighs of green .. thats the dye used to show leaks .

Rear pipes and its corrosion thats causes leaks .. if you are lucky and can get the bolts out then clean the surfaces .. scotch brite , new seals and refit .

Its not uncommon for these pipes to have pin hole corrosion at this joint though .. new seals wont help there .. your looking for a black spot on the pipe .. the more you dig at it the more white powder will come out .. thats ally corrosion .

You also use this test on any a/c pipe in a bracket .

The system holds 900 grams of R134a and 195 cm3 of oil .. ml .

The oil coats the inside of all the components .. its like a mist and is used to lubricate the compressor .

When degassing a system you will get some out but you will never get it all out hence we add oil as per the chart when items have been replaced .

A vacuum to the system will make moisture boil .. this can then be sucked out .. oil doesnt boil in a vacuum .

Fans will run at low speed when the a/c is turned on reguardless of wether the system is working or not .

Fan info can be found here ..

http://911uk.com/viewtopic.php?t=127681&highlight=

If the car has been left open to atmosphere or has been empty for a while then its wise to replace the dryer along with what ever work you are doing .

A/C rubber seals on the pipes .. these are designed to swell on contact with Pag oil .. always replace them when undertaking any work .

oil used is pag oil 46 .

When replaceing a compressor .. the new one will come pre filled with the entire amount of oil for the system .

You drain this out of the new compressor , you drain out the oil from the old compressor and measure it .. you then refill that amount of oil into the new compressor and fit it.

Never .. ever just fit a new compressor out of the box .. it will hydo lock it and destroy it ... this is for every car .. not just Porsche .

Images below show the system , the amount of oil per component that needs adding as a percentage of 195 cm3 , condensor leak and a few that i feel might be usefull .

Image from Pelican and the black / red arrow shows the rear pipe connection although LHD .

Gratitude to Pelican for their image and a well respected site that i think we all refer to .

I did say i would do a write up on a/c in the past .. sorry it took me a year .. i have a back log of things to do Very Happy
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maldren
Suzuka


Joined: 07 Oct 2016
Posts: 1001



PostPosted: Sun Feb 24, 2019 9:15 am    Post subject: Reply with quote

Brilliant, many thanks Iain. We really need a Wicki for things like this.
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Mike
2003 996.2 C2 Coupe Arctic Silver
 
  
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uk996
Silverstone


Joined: 09 Jan 2018
Posts: 110
Location: Home Counties


PostPosted: Sun Feb 24, 2019 10:25 am    Post subject: Reply with quote

Great info, thanks demort.
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77szymon
Monza


Joined: 14 Mar 2018
Posts: 219
Location: UK

2003 Porsche 996 Carrera 4S

PostPosted: Sun Feb 24, 2019 10:37 am    Post subject: Reply with quote

Nice info, funny as my compressor develop loud noise I was thinking it is bearing but it is or should I say was compressor as my car is off road and yesterday before pulling compressor out I have spin wheel and no funny noise at all could be gas/oil refill back compressor when I was jacking a car? From your instruction it is look like I'm running low on oil/gas.


How I can top up oil to compressor or this is something that shop will do?
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uk996
Silverstone


Joined: 09 Jan 2018
Posts: 110
Location: Home Counties


PostPosted: Sun Feb 24, 2019 1:17 pm    Post subject: Reply with quote

The system is evacuated, then the correct volume of oil and refrigerant added back in.

Take it to your nearest car AC maintenance people.
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Ghianightmare
Spa-Francorchamps


Joined: 25 Apr 2017
Posts: 261
Location: Dublin


PostPosted: Sun Feb 24, 2019 3:58 pm    Post subject: Reply with quote

Agree

See the recent thread on Air con whine. There are special air con servicing machines that some garages have that do the whole job.

Solved my whine.
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Ghianightmare
Spa-Francorchamps


Joined: 25 Apr 2017
Posts: 261
Location: Dublin


PostPosted: Sun Feb 24, 2019 3:58 pm    Post subject: Reply with quote

Forgot to say Thanks DeMort Thumb
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NedHan79
Spa-Francorchamps


Joined: 08 Nov 2018
Posts: 363



PostPosted: Sun Feb 24, 2019 5:10 pm    Post subject: Reply with quote

Great write up demort. I’d say that’ll stop a few boys scratching their heads.

A bit off topic but is there much to removing the air con all together?
Is it simply remove the pump and get a smaller belt?
Then just remove the pipes and condensers?
Mine dosnt work and I’d never use it anyway.
 
  
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deMort
Long Beach


Joined: 21 Mar 2015
Posts: 6155
Location: Brighton


PostPosted: Sun Feb 24, 2019 5:37 pm    Post subject: Reply with quote

NedHan79 wrote:
Great write up demort. I’d say that’ll stop a few boys scratching their heads.

A bit off topic but is there much to removing the air con all together?
Is it simply remove the pump and get a smaller belt?
Then just remove the pipes and condensers?
Mine dosnt work and I’d never use it anyway.


Not really .. i wouldn,t bother with the evaporator though .. dash out and not a huge weight saving.

Compressor is the biggest weight saveing as the rest is ally .
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NedHan79
Spa-Francorchamps


Joined: 08 Nov 2018
Posts: 363



PostPosted: Sun Feb 24, 2019 6:23 pm    Post subject: Reply with quote

I like the idea of removing the condensers for air flow though. Not really a weight saving issue. Just more on dumping what I don’t use
 
  
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deMort
Long Beach


Joined: 21 Mar 2015
Posts: 6155
Location: Brighton


PostPosted: Sun Feb 24, 2019 6:56 pm    Post subject: Reply with quote

Dont forget .. the conensors take the stone damage .. if removeing them then fit some sort of grill as protection if you havent already .

Only problem i see is getting the right sized belt .. perhaps the GT3 non a/c one would do Dont know
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deMort
Long Beach


Joined: 21 Mar 2015
Posts: 6155
Location: Brighton


PostPosted: Sun Feb 24, 2019 6:57 pm    Post subject: Reply with quote

Ref noisy compressors then a video here ..

https://www.youtube.com/watch?v=0exTwmhNtiE

You will see its only noisy in operation and not when just idleing .
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NedHan79
Spa-Francorchamps


Joined: 08 Nov 2018
Posts: 363



PostPosted: Sun Feb 24, 2019 7:16 pm    Post subject: Reply with quote

deMort wrote:
Dont forget .. the conensors take the stone damage .. if removeing them then fit some sort of grill as protection if you havent already .

Only problem i see is getting the right sized belt .. perhaps the GT3 non a/c one would do Dont know


I’ll start a new thread and see if anyone has been down that road.
You’ve been helpful as always
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deMort
Long Beach


Joined: 21 Mar 2015
Posts: 6155
Location: Brighton


PostPosted: Sun Feb 24, 2019 8:46 pm    Post subject: Reply with quote

Ill just clarify things ..

you will get some oil out of the system on a regass ..

Its normally in the region of 5-10 mils ... with 195 on these cars being the total amount .

You can not get all of the oil out .. this would involve removeing each component and letting them drain out for several hours .. again oil coats the inside of every component so removeing it is just not possible .

We can get an idea of what oil is in the system .. if nothing comes out then it will logically be low .. we would add more oil .

On a standard regass then i would add 10 mils oil and 10 mils of dye .

Moisture will come out of a system with a vacuum .. oil wont .

A vacuum test is also designed to check for leaks .. if you have one then the vacuum in the system will drop .. tha a/c machine knows this and will flag it as a fault ...

This is rather important to us guys .. if we refill a known leaking system then we could well be fined or possibly imprisoned if the authoritys find out ...

Saying the boss told me to do this is no excuse .. we are responsible for the save the planet stuff and we WILL be sent to prision for this .. i kid you not ... boss says regass .. i have to say no .. he says your sacked if not ... then im sacked .. thats how it goes .

If i even suspect there is a leak then i am duty bound not to refill the system .

current legislation .
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