Have a whining noise that happens when I either turn on my ac or heater. It’s noticeable but not obnoxiously loud, but goes away after turning off the ac. Shop said it’s the ac compressor going out. Could it also be another culprit? Ac belt going bad, or pulley and or tensioner?

 

Compressors can get noisier when the refrigerant charge is low. I would describe a low charge noise as a “growl”. When you say “whine” I think of an alternator type noise. Sounds like you are sure though that it is a/c related because you can turn it on and off with the a/c request button.

it would be helpful to know the service history for your a/c system, when you last thought your system was normal, any cooling performance issues you noticed in the hot weather, the weather conditions when you notice the noise.

 

[QUOTE=bookyoh;1602697787]Compressors can get noisier when the refrigerant charge is low. I would describe a low charge noise as a “growl”. When you say “whine” I think of an alternator type noise. Sounds like you are sure though that it is a/c related because you can turn it on and off with the a/c request button.

it would be helpful to know the service history for your a/c system, when you last thought your system was normal, any cooling performance issues you noticed in the hot weather, the weather conditions when you notice the noise.[/QUOT

ac system was flushed and full but noice still there. Just bought car but owner said that sound was never there before. Live in the bay so we have the best driving weather al year round

 

Let me correct myself, it’s not so much a whining noise more lower mid tone that can be heard once ac system is engaged. System needed more refrigerant and serviced but noise still was there after. Just bought car and has be driven in the Bay Area for the part 6 years so weather is really nice.

 

Are you hearing the compressor driving along at 30 mph? If so, that sounds unusual, especially at moderate ambients. On the other hand, if you are trying to hear it sitting at idle, then it is quite normal to hear a difference when cycling it on and off. Sitting in neutral and reving up and down or holding at a couple thousand RPM you will normally hear a difference on versus off too.

 

hmmm. Ok, I’ll drive it and listen to hear anything while going 30 mph

 

so noise comes on only when ac is on, so when I’m using front defroster I hear ac compressor cycling on and hear the noise a lot more when I am driving amd increasing speed to 30 mph and sounds like a low whining noise. If I just have the heater and just have the heat on the vents it doesn’t make any noise from the engine bay

 

I read that you recently had it recharged but it still sounds like it could be low charge noise. Perhaps you have a significant leak and and low again. A perfectly good system with very low a/c compressor noise may get noisy with low charge. Kind of difficult to check for low charge under mild ambient conditions though. If it was my car, I would
1. Take a mechanics stethoscope and listen to the compressor to confirm it is from the compressor.
2. add a half can (about 6 ounces) of r134a and see if the noise changed.

if adding refrigerant had no effect, then at least you know its not low charge noise.

 

so ac was serviced, my mechanic ran ac and noise was still present after the fact flushing and refilling

 

Have you used the stethoscope to verify it is the compressor and not one it the other pulleys?

 

I missed something you had written earlier. You’ve said the system was “flushed”. Do you really mean flushed or evacuated? The reason i ask is because a typical a/c service by a shop (not a do it your selfer like me) when a system is low on charge is to evacuate and then recharge. A flush is not typical unless you have had a compressor fail catastrophically and send bits of metal into the system.

 

let me rephrase that last comment. They said the refrigerant was about a 1 lb low and filled it and the noise still continued.

 

I have no further diagnostic ideas from a key pad and 2500 miles away. Some options to consider.
1. Get a second opinion from another shop.
2. Proactively replace it. The risk is you spend somewhere around $1000 and it is still the same; i.e. your original noise was typical.
3. Do nothing. Unless you set your a/c to auto, you wont use a/c much. See if it gets worse or you get used to it. The risk is your compressor has a mechanical problem and it breaks internally. This type of failure will require more extensive repair and more cost.

I was one of the engineers who worked on the launch of your Delphi V7 compressor back in 1996. Those compressors are pretty robust mechanically. They are tough. Wear out would not be typical in the low mileage lives that so many of our C5’s are subjected to. Extensive use (hundreds of hours of use) under low refrigerant charge can lead to excessive wear and reduced life. The reason for that is insufficient oil returning to the compressor’s crankcase. The refrigerant oil is in constant circulation and it relies on refrigerant flow through the a/c system for that oil to return to the compressor. Without sufficient oil in the crankcase, the bearings and connecting rod joints may wear more rapidly. There is another wear out condition, even with a correct refrigerant charge, that takes hundreds of hours and very high compressor RPM. To achieve this, imagine you drive on the Autobahn in Germany frequently on cool foggy (window defogging) conditions day after day, month after month. This leads to a reverse loading condition internally and more rapid wear. Im sure only a tiny fraction of C5 owners ever see hundreds of hours like this, even if they track their cars in cool conditions running their a/c.

 

having one of my good friends who is a master tech and very mechanically inclined. I’ll will keep you posted after diagnoses