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A/C questions

Mondof

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I’m new to here and decided to join after going through some of the threads. I bought a 1994 gmc burb 2500 with a 454 and rear air. I was wondering if anyone had thoughts on the gdp compressor w/ condenser packages. A r4 vs scroll compressor and if anyone has installed the AC Delco inline filter. Any help would appreciated.
 

WarWagon

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A r4 vs scroll compressor
Wrong question. That's going from bad to worse. The scroll just doesn't get enough RPM at idle to work well in the R4 package. You need a shorter belt as they even try and spin it faster. Note the rear air R4 is a larger ~11 cu compressor.

Rather get like a Sanden 508 compressor, bracket kit, and have the hoses made to fit. I believe some are using the Flex 7 Series to get the compressor to match up to hoses better.


You can order a compressor direct from the source as cheaply as the China knock off brands.


I have had nothing but trouble with the inline filter as they get so hot here the seals melt and they leak bad. The rear air TXV screen is a nasty job and a real small screen: enough to use the inline filter. You install them on the high pressure line as the compressor is the source of the debris. Before the condenser would protect it. But IMO too hot on compressor discharge so use it on the liquid line to the rear TXV to save that screen replacement job.

Do you know the age of the fan clutch? 5 years is their max life as they loose 200 RPM a year. Replace with a ACDelco fan clutch. Wire the aux fan via a relay to come on with the compressor.
 

Mondof

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I I’m not sure how old the ac system is it didn’t work when I bought it. Then I popped a hole in the lines going to the compressor. I recently replaced those along with the accumulator and orifice. It looked like someone replaced the txv. Charged the system and everything was working great until I noticed dye coming out of the ac delco compressor. I’m on a budget as I got three little kids and this is my wife’s shuttle for now.
 

Mondof

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Thanks one day when the wife can go back to work aka kids are grown i plan on putting in a diesel of some sort.
 

WarWagon

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Than simply replace the R4 with another R4. Wire the aux fan to come on with the compressor to help the POS R4 live a little longer.

Word: Just pour the gas down the 454 and drive it! The 454 easily outlives the 6.2 and 6.5 diesels. It was one of the most stupid simple and reliable engines out there. By the time you put a diesel of any kind in you can buy a tanker truck of gasoline. Further the EPA crackdowns really don't allow one to drop a diesel in place of a gas engine.

Buy a diesel rig and learn MPG is not TCO.
 

Mondof

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Is gdp a better pos or should I go with ac delco or does it not matter
 

WarWagon

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If your compressor was just leaking - just replace the compressor o-tube and accumulator. (generally required for warranty) Was it noisy? How did the orface tube look for catching debris? There may not be a need to replace the condenser and hunt down debris in the system.

GPD has a good rep on here. That or AC Delco are known as not the worst. For example the local parts store Murray R4 blew it's seals in the battery tray with an engine removed and similar bad reviews. Make sure it's the 11 CU rear air version as front only systems have a smaller displacement R4. IMO Odds favor an AC Delco part being the proper displacement.
 

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GPD makes a good product, they're all I installed. AC Delco R4's are rebadged four seasons units. The scroll compressor is nice for a single air unit, but it's not big enough for a dual air. Replace the condenser with a modern parallel flow design, I would replace the evap for the front as it is most likely half plugged or worse, a severe duty fan clutch as dual air units have alot of heat to pull out of the condenser, put a 99 expansion valve in the rear AC to prevent slugging and/or the rear lines filling up with oil, and put in a 99 .062 orifice tube in the front AC to improve idle AC performance.

I would run a new GPD compressor, or if you want to get fancy with it, Dirty Dingo sells brackets to install a 508 Sanden compressor(not sure if there is enough room for the 709), but it will not have as good of performance at idle as the Sanden compressors are not real efficient at lower RPM's, and the 508 is only available in up to a 9 cfm displacement.
 
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