Air Cond Loud Noise

I have a 2001 EB Suburban.
I have a strange and loud noise when I use my air conditioner.
In idle with the windows open and the air on max it works fine and blows cold with no noise.
If I am driving slow say around 30MPH a loud sound that is hard to describe, but I'll try: It last about 2 seconds they stops and repeats itself in another two seconds. When I turn the air off, the sound stops.
Do I need a new compressor or what could the problem be?

I checked the pressure. It is a little high, just slightly above 45 PSI which puts it into Yellow (caution) on my gauge. Is this too high?

Also when I left it in the garage running for awhile, I expected to see some condinsation on the ground but there was none. The pan was dry also. I searched for the evaporator housing drain tube, but could not find it. Any help here is appreciated.


Thanks, Bill!.

Sounds like the compressor is cycling on and off. You should have the a/c pressures checked with an a/c manifold guage set. It's probably low on 134.

I did check the pressure on the low pressure side and it was above 45 PSI. Is this high?

(..Or did you mean something else?)

45 is not too high but as the compressor is on, the pressure should drop. Eventually, when the pressure is below 21 PSI, the compressor should shut off and wait for the pressure to get above 44 again before coming on again.

See http://autoacrepairs.com/cycleswitchinfo.htm for more details.

It seems like you may have a bad pressure cycling switch and the compressor is cycling too much. The cycling switch can be replaced without evacuating the r134a.

Verify that the compressor goes on and off at the right pressures. If not, replace the switch.

//2000CAYukon

I did check the pressure on the low pressure side and it was above 45 PSI. Is this high?

(..Or did you mean something else?)


What they are telling you is you need one of these.
http://www.ackits.com/merchant2/merchant.mvc?Screen=PROD&Store_Code=AMA&Product_Code=66773

To safe and proper test your air system.
Pitch that one hose stop and go gauge.

You need to check the low and high side readings with compesser running at idle and at 2000 RPM and post back your pressure readings.

Have you added or What kind of freon did you put in it?
MT

I have put 1 12 ounce can of R134a over a year ago.

Even if the low pressure is reading a constant 45 psi which the compressor running, could it still be low?

This evening I will test the pressure when the compressor shuts off and post the results.

I still don't understand what the lout noise could be. It only makes the noise when the air cond is on. I have verified this many times. And it only make the repeated noise when the car is accelerating from stop. Once up to speed or slowing down I have not heard the noise.

The AC belt feels pretty tight.

Thanks for all the help!

I have put 1 12 ounce can of R134a over a year ago.

Even if the low pressure is reading a constant 45 psi which the compressor running, could it still be low?

This evening I will test the pressure when the compressor shuts off and post the results.

I still don't understand what the lout noise could be. It only makes the noise when the air cond is on. I have verified this many times. And it only make the repeated noise when the car is accelerating from stop. Once up to speed or slowing down I have not heard the noise.

The AC belt feels pretty tight.

Thanks for all the help!


How long has it been making the noise?
We need both low and high idle readings at idle and at 2000 RPM with compresser running.
And if noise is on acceleration speed the engine up from idle a few times and watch them gauges.

A constant 45 lbs on low side with compressor running is not quite right.
MT

It just started making the noise a few days ago. It happens about 60% of the time while accelerating.

I toom more reading last night and it stayed at a constant 55 this time. With the doors shut and running for 15 minutes, the compressor did not cycle off.

Another problem I noticed is if I turn the temperature 1/3 warmer, then back to cool the air does not go back to cool. It stays warm. This seems like a heat exchange valve or something is sticking. If I turn the air off then back on it is cool again.

I don't think my gauge can be connected to the high side. I will invest in some gauges and perform the idle up test.

Is it normal for the low side to increase when the air is turned off? My pressure is jumping to 90!

I know this is not right, but any ideas on what needs replaced?

It just started making the noise a few days ago. It happens about 60% of the time while accelerating.

I toom more reading last night and it stayed at a constant 55 this time. With the doors shut and running for 15 minutes, the compressor did not cycle off.

Another problem I noticed is if I turn the temperature 1/3 warmer, then back to cool the air does not go back to cool. It stays warm. This seems like a heat exchange valve or something is sticking. If I turn the air off then back on it is cool again.

I don't think my gauge can be connected to the high side. I will invest in some gauges and perform the idle up test.

Is it normal for the low side to increase when the air is turned off? My pressure is jumping to 90!

I know this is not right, but any ideas on what needs replaced?


With air off it is normal to see the low and high side pressure at underhood temp.
No problem there.
But the 45-55 lbs lbs on low with compresser runing is not right.
There is Problem there.
But we need both the low and high side with compreser running to evaen half way know what is going on.
Post them back when you get them .
MT

Got the gauges. At 92 Degrees in the garage and idling (500 RPM) I got
62 Low and 250 High.

When we tried to idle up to 2000RPM the AC belt broke immediately. It did not burn, but was just a clean rip. Since I could still turn the compressor with my hand I went an bought both belts becuase at 91K it was about time to replace them anyway plus the main belt must come off to replace the ac belt (correct?). (I was also just hoping I had a bad ac belt).

After replacing the belts we slowly revd the engine and got that famous loud sound at 1800RPM, so I quicly backed off the gas pedal to not rip another belt.

I did get readings at 1500 RPM
44 Low and 255 High.

Now what? Replace the compressor?
I'm done for the night but I did not check the compressor bolts to make sure it is secure.

The compressor looks like it is very hard to replace on a Surburban. Can it slide in from the small space behind the front bumper?

Thanks!

Got the gauges. At 92 Degrees in the garage and idling (500 RPM) I got
62 Low and 250 High.

When we tried to idle up to 2000RPM the AC belt broke immediately. It did not burn, but was just a clean rip. Since I could still turn the compressor with my hand I went an bought both belts becuase at 91K it was about time to replace them anyway plus the main belt must come off to replace the ac belt (correct?). (I was also just hoping I had a bad ac belt).

After replacing the belts we slowly revd the engine and got that famous loud sound at 1800RPM, so I quicly backed off the gas pedal to not rip another belt.

I did get readings at 1500 RPM
44 Low and 255 High.

Now what? Replace the compressor?
I'm done for the night but I did not check the compressor bolts to make sure it is secure.

The compressor looks like it is very hard to replace on a Surburban. Can it slide in from the small space behind the front bumper?

Thanks!


Does it have rear air?
High side is good pressure.
But low side if to high for good cooling.
But i am not sure on what the noise is.
Does it act like belt slipping or making noise.
I would evucate system and check orfice tube and oil in the system
And refill with set charge of freon and oil.
If orfice tube is full of plastic or metal replace compresser.
Also here is a good air cond link.
http://www.autoacforum.com/

The car does have rear air (evaporator etc).

I'm not sure if the noise is a slipping belt or something else. I am starting to think it may be the tension pulley. What would the two different sounds make, a slipping belt or a pulley that is bad. I have hear that these are known to go bad in these cars.

Thanks, Bill.

You know, it could be the tensioner bearing or even the alternator bearings. With the increased load on the alternator when the A/C is on, I wouldn't be surprised. If you have a long enough screwdriver you can use it as a stethescope to listen to the bearings in the tensioner or the alternator. I once had an alternator go bad and it sounded like an exhaust leak. I was easily able to narrow it down using a mechanics stethescope.

You know, it could be the tensioner bearing or even the alternator bearings. With the increased load on the alternator when the A/C is on, I wouldn't be surprised. If you have a long enough screwdriver you can use it as a stethescope to listen to the bearings in the tensioner or the alternator. I once had an alternator go bad and it sounded like an exhaust leak. I was easily able to narrow it down using a mechanics stethescope.

The alternator is on a different belt and the noise stops when the AC is off so I have isolated it to the ac belt. It could be the tensioner on the AC belt though.

Replaced the compressor with a new one, the dryer, and the OT. All is well now.

Replaced the compressor with a new one, the dryer, and the OT. All is well now.

Proper testing before shotgunning/throwing parts at it would be in order.
MT