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AC Compressor vibration

95 k1500

By 95 k1500
in Ask A GM Technician

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95 k1500 New Member

95 k1500

Posted
Posted

I have a 1995 K1500 with a 5.7

 

A couple of years ago, the bearings in my ac compressor went to pot. I (stupidly) bought a used compressor and had it put on my truck. The bearings were fine, but the seals were bad and it wouldn't hold charge.

 

Fast forward to yesterday, I bought a new compressor from Autozone and, since the system had no charge, I replaced the compressor myself and this morning took it to a shop to have the system vacuumed and recharged.

 

When I got the truck back, the air is ice cold, however there is an incredibly loud hum in the cab of the truck when the air is running and the truck is at idle. At speed, everything is fine, but coming to a stop at a light 5-10 mph) or sitting at idle causes the noise.

 

I popped the hood and had my wife press the button to engage the a/c. The clutch engages and the noise starts.

 

Any thoughts on what the problem could be? Would the system be charged to too high of pressure? I am really hoping it isn't the compressor because I'm not really in the mood to remove it again :banghead:

gmtech4 Senior Enthusiast

gmtech4

Posted
Posted

The machine puts in what the truck sticker says so over charge is not the problem,

 

It's mounted to the engine with no rubber mounts , if it's vibrating it's the compressor and nothing more , but have a real tech look at it before you have it recovered and warranty it ,

 

Do you see a sticker on the truck and the receipt with matching recharge #s?

 

Did he put oil in the system ? .

95 k1500 New Member

95 k1500

Posted
  • Author
Posted

The machine puts in what the truck sticker says so over charge is not the problem,

 

It's mounted to the engine with no rubber mounts , if it's vibrating it's the compressor and nothing more , but have a real tech look at it before you have it recovered and warranty it ,

 

Do you see a sticker on the truck and the receipt with matching recharge #s?

 

Did he put oil in the system ? .

The receipt says that I was billed for was evacuate & recharge a/c system and for 2lbs of R134a refrigerant.

 

I would hope they'd remember to add some oil to the system, especially after vacuuming everything out.

 

The only sticker that is on the truck is on top of the accumulator. It says to use #12345922 or equivalent synthetic oil and 2.0 lbs of R134a refrigerant or the system will be damaged.

 

I will have to call on Monday to get some more details about what was done. I didn't take it to a dealership to have this service work done. I took it to a Goodyear service center about a mile down the road.

 

Thanks for the reply

gmtech4 Senior Enthusiast

gmtech4

Posted
Posted

Oil is always a guess IMO , each component holds so much . Adding during a recharge is about 2oz ., or what came out during a recovery(some machines ),

 

Take it back but you supplied the compressor so idk what they'll do for ya

 

Good luck

Doug_Scott Senior Enthusiast

Doug_Scott

Posted
Posted

Common misconception that vacuum is for cleaning out the system. All the vacuum does is lower the pressure inside the system to cause any moisture to boil at room temperature, and the vacuum will pull the "steam" out. It takes a while for it all to get pulled out. Oil will not be removed by vacuum. When you got the compressor it should have come with some papers. One of those papers should tell you how much you need to add to the compressor before installing it. Some of the older compressors even had dipsticks to check(after system discharged). Back in the day when recovering refrigerant had not been invented yet, I would discharge the system though a trap to see how much oil came out. Usually drained it slow enough to not lose any oil. The shop that did the work should have at least asked you about if you added any oil.

 

Since you did the labour yourself, double check all the lines and make sure they are all securely attached to the various body mounts on the way to condenser and evaporator. You don't say, so I assume you did not change receiver dryer and fixed orifice tube. The receiver dryer (also called accumulator by some) will be useless now. the desiccant bag is not reusable, and once it has absorbed its capacity of moisture, any moisture that appears will stop the a/c pretty quick(will plug fixed orifice tube).

95 k1500 New Member

95 k1500

Posted
  • Author
Posted

The only work I did was to replace the compressor. The instructions that came in the box said that there was oil in the compressor.

 

I drove the truck this morning approx. 50 miles on a round trip and the only issue I found was braking to a stop (from 10 down to 5 mph) there was a sound like an airplane turbine powering down (if that makes sense)

 

Is it possible that there is a break-in period for this type of part that I am not aware of? The noise seemed to be more prominent yesterday especially when the truck was idling in gear and idling in park.

Doug_Scott Senior Enthusiast

Doug_Scott

Posted
Posted

Even though you did not touch anything else in the system does not mean it is in the correct location, with the correct hold down/guide parts. I have found that when replacing a compressor the high and low side hoses are not always in the exact same location and angle on replacement compressor. You could also check the evaporator to make sure it is still tight inside the heater box. The way you describe the vibration really sounds like something in the a/c system is touching something on the body of vehicle and is creating a drone.

  • 5 years later...
RanDmaN75 New Member

RanDmaN75

Posted
Posted

I am having the same issue. On my second compressor and both were oiled properly. Both compressors vibrate at idle. I recharged my system and the vibration didn’t start until I added the R134. And got worse the closer i got to max fill.

  • 3 years later...
Jheberer93 New Member

Jheberer93

Posted
Posted

I have the exact truck and issue at idle except it’s a 4.3. Harsh vibration at ide and it almost sounds like the transmission is growling but when I turn the ac off it runs fine. Did you ever sort out the issue? 

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