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gilessav
Monza
Joined: 04 Jan 2013
Posts: 240
Location: Oxford UK
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 Posted: Sun Feb 03, 2019 12:17 pm Post subject: C4S whine
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Afternoon all,
Just a quick one that I've been experiencing a whine from my C4S more recently (not that it's been our much with the salt and snow around).
This is more pronounced at lower speeds (or more audible) but resolves when the aircon is turned off. Reading around with the fact that the aircon switched off removes the noise, it is reasonable to assume it's either in need of a regas and the pump is noisy as a result or something like the aircon compressor is on the way?
Aircon does still blow cold but tough to tell this time of year, but not as icy as I remember. Last regas with new rads was early 2014 so maybe points this way?
cheers,
Giles.
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Previously LHD 964
Currently 2004 C4S
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Alex
Le Mans
Joined: 06 Mar 2014
Posts: 15757
Location: The Ribble Valley, Lancashire
2000 Porsche 996 Carrera 4
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| Posted: Sun Feb 03, 2019 12:22 pm Post subject:
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Whining aircon pump is mostly due to starting to run low on gas (and lubricant). Suggest you get the system regased (and pressure tested).
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2000 Manual 996 C4 Arctic Silver Convertible
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gilessav
Monza
Joined: 04 Jan 2013
Posts: 240
Location: Oxford UK
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| Posted: Sun Feb 03, 2019 12:33 pm Post subject:
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Cheers Alex,
Service due in late Feb/March so will get my Indy to check and as you say pressure test/re-gas...not sure she'll get out much unless there as some dry days before then, do try and typically use every 7-10 days to keep the fluids moving usually!
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Previously LHD 964
Currently 2004 C4S
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Alex
Le Mans
Joined: 06 Mar 2014
Posts: 15757
Location: The Ribble Valley, Lancashire
2000 Porsche 996 Carrera 4
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| Posted: Sun Feb 03, 2019 12:38 pm Post subject:
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For a seconds there I got excited as I read it your mechanic is a 'she' 
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2000 Manual 996 C4 Arctic Silver Convertible
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Ghianightmare
Spa-Francorchamps
Joined: 25 Apr 2017
Posts: 270
Location: Dublin
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| Posted: Sun Feb 03, 2019 3:04 pm Post subject:
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I have this also - comes in at around 2,000 RPM. I had it checked and pressure was too high, so it was bled and noise went away for a day and then came back... haven’t taken it back since. I just turn off the A/C if I’m in traffic and there isn’t much moisture in the air.
In thinking it needs lube in it as mentioned above.
If you solve your prob, please advize what it was!
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2002 Seal Grey C4S
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deMort
Long Beach
Joined: 21 Mar 2015
Posts: 6312
Location: Brighton
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| Posted: Sun Feb 03, 2019 5:26 pm Post subject:
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| Ghianightmare wrote: | I have this also - comes in at around 2,000 RPM. I had it checked and pressure was too high, so it was bled and noise went away for a day and then came back... haven’t taken it back since. I just turn off the A/C if I’m in traffic and there isn’t much moisture in the air.
In thinking it needs lube in it as mentioned above.
If you solve your prob, please advize what it was! |
Alex has already answered the OP question but im interested in your fault ..
Low gass is the normally cause of noises that go away with the a/c being turned off ..
To have a pressure thats too high .. strange .. it would happen when refilling and too much gass had been added if they bled some out .
The usual running pressures are 2bar low side and 10 plus on the high side .. ive seen the high side go upto 20 bar and i belive the dump for over pressure is 38 bar .
Im curious as to how your garage checked this .. i would normally remove all the gass then refill to the correct amount , then check the pressures whilst running to confirm operation ..
More details please young man !
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My Daughter's Crowdfunding page Here
7pm - 9pm
Now At An Indy.
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Ghianightmare
Spa-Francorchamps
Joined: 25 Apr 2017
Posts: 270
Location: Dublin
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| Posted: Sun Feb 03, 2019 11:45 pm Post subject:
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My non technical translation of what happened - the air conditioning man connected pressure gauge - said it’s too high (showed me what it was and told me what it should be) and something along the lines of they didn’t do something right the last time it was serviced and that was why it was too high - I think there was air in the system?? - so he went and got his bottles of refrigerant and charged/bled the system and made sure the pressure was correct - and the noise was gone and I drove off and the noise was still gone, but it was back the next day, and I just never went back as I used all of my spare time over last summer to do the suspension!!!
That is the best I can offer. It was 8 months ago and I wasn’t really paying too much attention...he only charged me €20 as it was Friday evening and we were both in a hurry!
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2002 Seal Grey C4S
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deMort
Long Beach
Joined: 21 Mar 2015
Posts: 6312
Location: Brighton
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| Posted: Mon Feb 04, 2019 7:31 pm Post subject:
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Thats a very old school way of doing it .. reading off the pressures to get the correct amount of gass in it ..
Fine if you know the pressure values i guess ... but the high side does vary .. i could go into a long winded explaination but suffice to say the point at which it changes from a vapour to a gass is in the wrong place and causes noises with an incorrect amount of gass in the system .
i would tend to say .. have it regassed and put 900 grams in .. halfords etc will do this pretty cheap ..
After that if you still have a whine then its a bit unusual but it also may well fix the problem ... i think it will anyways .
With reguards to " lub " its Pag oil and its not possible to remove it from a system and then refill with the correct amount .. its not possible to find out how much is in the system ..
All we can do is add the correct amount thats listed for each item that is changed .
I know it has been mentioned in the past as possible .. not without replacing the entire a/c system im afraid .
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Ghianightmare
Spa-Francorchamps
Joined: 25 Apr 2017
Posts: 270
Location: Dublin
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| Posted: Mon Feb 04, 2019 9:54 pm Post subject:
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Thanks Demort - I haven’t ever read up on A/C - I didn’t need to during my 18 years of Land Rover can classic car ownership  - so I wasn’t in a position to question what the guy was talking about.
He did say it would be a quick fix as he was about to close so I’m not feeling hard done by.
When you say put 900 grams in - is that the weight of the gas I should add to what is there already?
Apologies to OP for thread hijack
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2002 Seal Grey C4S
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Alex
Le Mans
Joined: 06 Mar 2014
Posts: 15757
Location: The Ribble Valley, Lancashire
2000 Porsche 996 Carrera 4
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| Posted: Mon Feb 04, 2019 10:04 pm Post subject:
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No, it's the amount that should go in an empty vac'd down system. and then there's the amount of lubricant (195cc) that needs to go in with it.
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2000 Manual 996 C4 Arctic Silver Convertible
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gilessav
Monza
Joined: 04 Jan 2013
Posts: 240
Location: Oxford UK
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| Posted: Mon Feb 04, 2019 10:15 pm Post subject:
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Thanks guys for the answers and I'll report back once I get checked in the spring, also seems to have generated some more air-con related points so I'm always learning 
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Previously LHD 964
Currently 2004 C4S
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deMort
Long Beach
Joined: 21 Mar 2015
Posts: 6312
Location: Brighton
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| Posted: Tue Feb 05, 2019 7:36 pm Post subject:
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Can i just add .. dont put 195 of oil in the system ( Sorry Alex ) .. thats for a totally empty system and is the total amount thats in the car ... ill explain in detail if needed .
Too much oil will destroy the compressor .
900 grams of gass .. the machines are set so you just punch in the numbers then add what oil amount .. for a stand alone gass replacement i would add 5 mls oil and 5 mls dye depending on what the machine took out .
For a condensor i would add 15 mls per side (book amount is 20 but its better to be under than over on the oil.. plus i add when regassing) .. and so on for each component .
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My Daughter's Crowdfunding page Here
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GMG
Spa-Francorchamps
Joined: 07 Jan 2018
Posts: 346
Location: Devon
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| Posted: Tue Feb 05, 2019 7:56 pm Post subject:
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...so Iain as you know I am replacing the drier and both condensers after which I will get it regassed...do I pour pag oil into each condenser and an amount to the drier or ask the garage to add an extra amount to the system when it's regassed?
Thanks buddy.
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deMort
Long Beach
Joined: 21 Mar 2015
Posts: 6312
Location: Brighton
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| Posted: Tue Feb 05, 2019 8:11 pm Post subject:
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Get them to add 30 mls for both condensors ... dont add it yourself ... you can in theory but you will need an exact amount and the a/c machine will do just that .
The book amount .. well the rough guide they give us states 40 but i personnely dont like to push my chances .. you have no idea what people have added in the past .. and ive added this amount for many years now .
When replacing an entire a/c system then you have to add oil this way .. ive done it twice in my life .. a little nerve racking i can tell you .. you cant just get an a/c machine to dump 150 plus of oil in .. its a large slug of oil that will hit the compressor and kill it .
Just for info .. water / moisture will boil in a vacuum and can be drawn out with an a/c machine .. oil doesnt boil and cant be drawn out this way .
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GMG
Spa-Francorchamps
Joined: 07 Jan 2018
Posts: 346
Location: Devon
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| Posted: Tue Feb 05, 2019 8:18 pm Post subject:
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Thanks Iain...Will follow your advice, or rather I will instruct the garage to...
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Ghianightmare
Spa-Francorchamps
Joined: 25 Apr 2017
Posts: 270
Location: Dublin
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| Posted: Fri Feb 08, 2019 8:03 pm Post subject:
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Spurred on by this thread, I decided to address my whining a/c.
I had a look at all of the options here in Dublin and decided to go to a place near me where they had a machine that drains cleans checks and re gasses the a/c system. I googled the machine make and model before I called them (they referred to it by name on the website) and by all accounts it seems to be a comprehensive bit of kit.
When I spoke to the service manager (who is contemplating buying a 996.2) he was able to talk about a/c in a very informed manner. When I asked about replacing the drier and the whine, he said if there is moisture in the system and the drier is overwhelmed, it can cause resonance as the refrigerant is being pumped through, but the wouldn’t know for sure. He also advises that the machine would dry out the system and restore the existing drier if it wasn’t too bad.
He could do it immediately as there isn’t much manpower required so I bit the bullet.
The process took about 90 min. The hook up said machine and it measures the refrigerant in the system. 290g in mine - so that was the first problem. Then it extracts the oil - it was low too. Then it puts in dye and checks for leaks. Then it extracts any moisture - which in my case took a while. Finally it replaces the oil and the gas. All without any human input. The dye is similar to the oil and is left in there for future reference and leak tracing.
Cost €146. Result - silence restored, air noticeably colder, and a happy owner. Confidence that it is done properly.
So if you have a whine, I reccommend a similar comprehensive restoration of the system as opposed to a quick recharge at Halfords.
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2002 Seal Grey C4S
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deMort
Long Beach
Joined: 21 Mar 2015
Posts: 6312
Location: Brighton
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| Posted: Fri Feb 08, 2019 8:28 pm Post subject:
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Young man thats excellent .. the gass was far too low , there should be 900 in it not 290 ... spurred on was a good call i think!
A vacuum which is what the machine does will suck out moisture .. but to be honest its a 24 hour type of thing to be fully effective if a system is badly contaminated .
replaceing a dryer .. its normally done when the system has been open to atmosphere for a while ... or a totally empty system as if the gass leaks out then mositure can get in .
Noise from the dryer .. yup possible i guess .. new one on me but im not going to doubt it .
I would argue about the oil lvl .. you can measure whats comes out but not whats actually in the system .. long depth answer if needed so ill leave it at that but as long as they added some .. which i know full well they have then you are fine .
Modern machines are far .. far better than the old ways and you have no noise and a good a/c .. result
Edit ..
Ill also add thats an mot ramp and the geo kit in the back ground isnt cheap , again the a/c machine is not going to be cheap either .. any garage that invests in equipment is worth useing .
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My Daughter's Crowdfunding page Here
7pm - 9pm
Now At An Indy.
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Ghianightmare
Spa-Francorchamps
Joined: 25 Apr 2017
Posts: 270
Location: Dublin
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| Posted: Fri Feb 08, 2019 9:11 pm Post subject:
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Eagle eyes deMort!
They have a wheel straightening machine, several types of scopes, many types of code readers, 5 Other bays with lifts of some
Kind in all. A pretty comprehensive set up!
Here is the info on the a/c servicing and the machine they used.
http://www.greenautoservice.ie/air-conditioning.html
I won’t burden you to explain re the moisture, all I know is that it works good now!
They have a second machine for the newer gas (post 2012 Porsches) but that gas costs about 3 times the price. I think he said the machine was circa €6k
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2002 Seal Grey C4S
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Robertb
Long Beach
Joined: 01 Sep 2003
Posts: 6890
Location: South Oxfordshire
2002 Porsche 996 Carrera 4S
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| Posted: Sat Feb 09, 2019 12:20 am Post subject:
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Great thread, very informative. I’ve had a ‘grumbly’ compressor for ages, had an air con recharge and it helped, but not perfect. Clearly I need to find a specialist.
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"911- the guilt-free supercar"
Current: 2003 C4S Coupe, seal/black
Ex: '02 C4S Coupe, '96 993 Targa, '88 Carrera Sport Coupe
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Alex
Le Mans
Joined: 06 Mar 2014
Posts: 15757
Location: The Ribble Valley, Lancashire
2000 Porsche 996 Carrera 4
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| Posted: Sat Feb 09, 2019 9:35 am Post subject:
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| Ghianightmare wrote: |
So if you have a whine, I recommend a similar comprehensive restoration of the system as opposed to a quick recharge at Halfords. |
Don't Halfords do the same process with their Air Con service:
https://www.halfords.com/advice/motoring/service/halfords-car-air-conditioning-services
To quote:
Air Con Recharge and Clean Service
For the ultimate air con service, our experts can recharge your air con and clean the system at the same time for only £60 (€65).
Included within the recharge and clean service is the air con cleaner product.
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2000 Manual 996 C4 Arctic Silver Convertible
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