C4S whine

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.

Whining aircon pump is mostly due to starting to run low on gas (and lubricant). Suggest you get the system regased (and pressure tested).

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!

For a seconds there I got excited as I read it your mechanic is a 'she' :grin:

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 !

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!

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 .

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

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.

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 :thumb:

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 .

...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.

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 .

Thanks Iain...Will follow your advice, or rather I will instruct the garage to...