AC repair

[wildcatjason]

My AC compressor went out before I did my cummins swap and I was wonder if anyone here has fixed their AC. My AC is all 1/2 ton 1988 suburban with rear AC I have the rear AC it was a 350 before I swapped it. It makes a loud shreal if you turn it on. My question is do I need to replace the compressor, orifice and dryer like I've read or can I just replace the compressor and run it? Is there something I'm missing. I don't wanna dump a bunch of money, but I want if fixed right the first time. Thanks.

 

[austinado16]

A/C repair is spendy. Yes, you'll need a new compressor, receiver-dryer, and the oriface/filter. It's a good idea to replace all the o-rings you can get to, with new viton versions. You'll also need Ester 100 oil to put into the new compressor. Then you'll need to pull a vacuum on the system in order to boil out all the moisture. Once you've done that for about an hour or more, the system can be re-charged with R134a. Fill it so you get about 25" of suction with the engine at about 1,500-2,000rpm. Don't overfill, or it won't make good cold.

 

[wildcatjason]

A/C repair is spendy. Yes, you'll need a new compressor, receiver-dryer, and the oriface/filter. It's a good idea to replace all the o-rings you can get to, with new viton versions. You'll also need Ester 100 oil to put into the new compressor. Then you'll need to pull a vacuum on the system in order to boil out all the moisture. Once you've done that for about an hour or more, the system can be re-charged with R134a. Fill it so you get about 25" of suction with the engine at about 1,500-2,000rpm. Don't overfill, or it won't make good cold.

Do you know if there is a orifice for the rear too?

 

[chengny]

TSB on this (only for model years 85-86, but still may be helpful - espcially the orifice screen info):

NUMBER: 86-B-45

GROUP: 1B-Air Conditioning

DATE: March, 1986
SUBJECT: REAR AIR CONDITIONING

MODELS: 1984-1985 C, K, G MODELS WITH REAR AIR CONDITIONING

You must be registered for see images attach

The thermal expansion valve (Refer to Figure No. 1) used in rear air conditioning units, contains a small "funnel shaped" screen. If this screen becomes plugged, the rear air conditioning unit will not function properly.

You must be registered for see images attach

Harrison Radiator corrected this situation by installing the screen in the opposite direction from the original position. When viewed through the opening in the expansion valve fitting, the screen
should be positioned as it appears in Figure No. 2. This allows any debris in the system to collect around the base of the screen, while permitting the rear air to function properly. Vehicles which are found to have plugged filter screens should have the screen cleaned and the direction reversed so it is the same as the valve shown in Figure No. 2.


Unrelated to your issue:

OEM condenser is not the problem, they are completely compatible with 134-a.

Think about it - if the refrigerant in the front system is flowing/condensing but not the back, there is an obstruction in the rear piping.

Dump the entire system (no way to isolate the rear) and clean the screen as per the TSB.

Close up, evacuate the combined systems and recharge per chart (5lb 4oz):

You must be registered for see images attach

 

[swagger]

Jerry,
Good info!!
didn't know that
Steve

 

[wildcatjason]

My compressor was making a terrible noise and the clutch isnt seized so I am guessing parts got thrown.

 

[chengny]

A failed compressor doesn't squeal (shreal?) - that sound would come from the belt and or clutch.

A seized compressor won't turn. So when the clutch pulls in (and the pulley is mechanically coupled to the locked up compressor rotating assembly) the drive belt scream as it gets dragged across the pulley interface.

But anyway to your original question:

If the compressor was running fine up to the moment it failed - and it seized only once and never rotated again - you may get lucky. The entire system may not have been ruined.

If, on the other hand, the compressor suffered a slow, agonizing death (over a period of days/weeks) every part of the A/C system is most likely contaminated.


The slow destruction and continued use of a failing compressor results in what is known as "black death".

In other words, the entire system is shot (i.e piping, heat exchangers, metering devices, filters/screens, receiver etc.). There will be burnt oil and metal particles throughout.

Without some serious attention it can never be functional again. It will need to be broken up into sections and thoroughly flushed.

If there is still pressure in the system, a quick test:

Release some refrigerant/oil from a service port (push in on the schrader valve). Capture what blasts out into a clean white rag and inspect.

No pressure left? Pull the accumulater/drier and cut it open.

Black death is indicated by very dark oil (almost black - hence the term), visible metal paticles and an obvious burnt smell.

 

[wildcatjason]

A failed compressor doesn't squeal (shreal?) - that sound would come from the belt and or clutch.

A seized compressor won't turn. So when the clutch pulls in (and the pulley is mechanically coupled to the locked up compressor rotating assembly) the drive belt scream as it gets dragged across the pulley interface.

But anyway to your original question:

If the compressor was running fine up to the moment it failed - and it seized only once and never rotated again - you may get lucky. The entire system may not have been ruined.

If, on the other hand, the compressor suffered a slow, agonizing death (over a period of days/weeks) every part of the A/C system is most likely contaminated.


The slow destruction and continued use of a failing compressor results in what is known as "black death".

In other words, the entire system is shot (i.e piping, heat exchangers, metering devices, filters/screens, receiver etc.). There will be burnt oil and metal particles throughout.

Without some serious attention it can never be functional again. It will need to be broken up into sections and thoroughly flushed.

If there is still pressure in the system, a quick test:

Release some refrigerant/oil from a service port (push in on the schrader valve). Capture what blasts out into a clean white rag and inspect.

No pressure left? Pull the accumulater/drier and cut it open.

Black death is indicated by very dark oil (almost black - hence the term), visible metal paticles and an obvious burnt smell.

I'll check it out. It didnt sound like a belt. It is more of a terrible clattering noise. I can spin the clutch with my hand.

 

[wildcatjason]

The oil from the back of the compressor looked okay and didnt smell funny. It was kind of a dark tinted yellow. I didn't see any metal and still spins okay without issue. I will take the accumulator apart before I put a cent into it. Thanks again for the advice.