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I need to decide on an R4

Dave5701 on Fri February 25, 2011 12:50 PM User is offlineView users profile

Year: 79
Make: vette
Engine Size: 350
Refrigerant Type: R134
Country of Origin: United States

I am taking an Auto AC class at a Jr. College so I can fix this and have some help. I am ready to pull the trigger and I dont want to jump off a cliff -- at least in a wrong direction. The car has the complete AC system there. It does not work. It is not charged so I am anticipating a leak. Compressor Clutch does come on. It is R12 or was. I know the condenser needs replacing to a parallel flow and I will do that. Now. What about the compressor?? I am assuming it is the original one. It may work, may not. SHould I just go ahead and get another R4 (I hope I am using the right working here, it is the short fat one, like a pancake type) just because the original is old. Or should I bite the bullet and get another better quality one, (Ihave been told Sanden??) and put it in. If I get a completely different model, I may have bracket issues and working on this car is already enough of a PITA!!!!. SO whats the scoop on if I change out orfice tube, flush system, put in new R4, new parallel flow condenser, convert to R134. Would this be about as good as doing the same with a different type of compressor. I would like to say with the R4 just because all the mounting stuff is there.

Cussboy on Fri February 25, 2011 4:46 PM User is offline

I believe changing to Sanden requires new brackets and new hoses/hose ends/adapters. And that adds to the cost as well.

I put a brand new R4 in my 1994 Suburban about 10 months ago. I've read a lot that say to stay away from rebuilt R4 compressors, that they're crap. See board sponsor or AutoZone for brand new R4, under $250 I believe.

GM Tech on Fri February 25, 2011 7:05 PM User is offline

Impress your instructor and reseal that leaky old R-4. Test it first to may sure it is not knocking- then put a new shaft seal and o-rings in it- they are available on-line..

The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

mk378 on Fri February 25, 2011 9:43 PM User is offline

While the system is still put together, leak check it to identify what will need repair or replacement. A static charge of a small amount of R-134a can be used for that purpose. Do not run the compressor without a full charge of refrigerant and the proper oil for that refrigerant.

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