"moaning" when ac is turned on '98 qx4

[clarosa]

So when I turn on my ac there is a "moaning" type of noise and the air doesn't come out quite as cold as it should be. Does anyone know what this could be?

[Towncivilian]

Turn A/C off and use only the fan, is the noise still there?

Change the in-cabin air filter too.

[clarosa]

The the moaning sound is when the compressor comes on. When my coolant was too low for the compressor to kick in, it didn't make the noise.

[Towncivilian]

Your compressor may be low on oil, or the drive belt for the compressor is worn or loose. I'd replace the belt first with an OEM one (about $20 @ dealer) and be sure it's tightened at proper torque specs. If that doesn't help, get the A/C system evacuated and recharged.

[clarosa]

As you can tell, I am not very familiar with AC systems so bare with me, but to me it almost sounds more like an oil problem when I listen to it. Is there a way to refill the oil? I think I will change the belt as well. How difficult is it to change the belt and or oil?

[clarosa]

i did put leak seal which had oil in it which made my compressor start working again, but it is kind of noisey tho.

[Towncivilian]

If you attempt to recharge the system yourself using the cans of refrigerant/oil with gauges on them, you have the possibility of both introducing contaminants into the system as well as overfilling. Best to leave it up to the pros - and not the shop on the corner who tout experts just because summer rolled around; someone more reputable (dealer charges $150 for evac/fill I believe). "Leak stop" crap also has the potential to worsen things further if you use too much of it. As for the drive belt, I don't have any first-hand experience with it, but you can glance at the service manual on page MA-13.

[clarosa]

Yea, I am selling the vehicle so I was trying to do a quick fix and not dump more money into it. I already had to replace the starter and vavle gaskets. If all it costs is $150 that would be doable for me. I appreciate the advice though and this helps me a lot.

[yeldogt]

It is best not to mess around with the refrigerant system. The best one can do is to make sure the belts are correct and that the compressor is cycling correctly. The AC system does not have "coolant" it has "refrigerant" .

Most likely your problem was the system was too low or completely out of refrigerant and you added enough for the "low refrigerant" sensor to be satisfied -- the compressor would then work. What people don't understand is that you don't want to add extra oil or sealers into the system -- too much oil is very bad for the compressor and some shops will not work on systems that have sealers in them. The noise could be from the oil being sucked into the compressor? You should always take your car to an AC shop for proper diagnosis -- that way you know what is up. Lots of things can be wrong and many don't cost much to fix correctly. Doing the incorrect thing --- like overfilling the system -- can kill it.

One of my old cars that I use in the summer looses refrigerant somehow -- we have tried to find it. Sometimes, it works from year to year other times it is not cold enough -- but we know that the problem is a simple loss of a small amount of refrigerant -- so we add a bit using the correct tools and that is that. Now, if it stopped working completely then that would tell me the leak is larger and possibly I have another problem.

When you have a system not working at all -- the system is normally empty are close to it. If you refill it without finding the leak -- it will just leak out and you will be doing it again. Many times the leak can be quickly found and fixed -- then the system is properly evacuated of all air and moisture and refilled correctly. It can then work correctly for many years without any problems.

You only use sealers as a last resort - and never add oil unless it is indicated. If you don't properly evacuate the system the moisture will attack the inner--workings of the system -- it may work fine that year and then completely fail the next summer.

People often add refrigerant -- say to themselves two years later when the system fails that they got two extra years out of it ........when actually they killed it and should have had it properly fixed when the problem first started.

[ARKQX33V6]

Yeldogt has it right. AC compressors work similar to air compressors but they need it very clean. Freon and there are many types must be pristine, no moisture and adding oil or lubrication without knowing the contents of the compressor is disaster. A trained person with years of experience should work on these system, not back yard mechanics, DIY can and do save a lot but there are times to back away and this is one of them.

An electrically driven compressor is a bit easier to diagnose because amperage can be read, but a 3.3. or 3.5 engine produces hp and torque that most of us cannot read. A compressor under compression needs a gas to be compressed and during that time amps x voltage are readily acquired and an understanding of HP can be determined and an electrically operated compressor has a name plate to offer and compare readings.

Auto compressors are big units offering 2-5 tons of cooling. With multi cylinder swash plate design they are complex and pricy to replace.

Finding a reputable repair depot is as easy as going to your Nissan dealer, because certain things need expertise and this is an area not to be a cheap so and so.

Selling a crapped out car leaves a bad taste in my mouth, I think it would be to both the seller's and buyer's advantage to know the compressor is failing and that you have not mickey moused with it. Being up front may not get you the most out of a used car but it may keep you out of a court room

[mo21]

I have a similar problem. when its really hot out and my car is not moving but the ac on its starting to overheat but when i drive its OK. sometimes when i stop its good too only when its over 85 outside then i get this issue. any idea as of what will cause this?

[ARKQX33V6]

MO21. That car is exhibiting a dirty rad or a partial plugged up rad at the very least.

[ARKQX33V6]

There is not enough cooling air via the fan at stopped times. With the A/C on your idle goes up, confirm this.

[mo21]

correct...