b9box
12-07-2012, 08:40 PM
I've been rebuilding/servicing my automotive AC systems for 30 years, up to this point only R-12 on many different Chevy trucks. My background is electronics engineer, but I have a reasonable understanding of refrigeration, lost count how many I've built/recharged over the years. Perhaps just short on some of the little details (which is everything as we all know.) This is first R134a though.
I completely rebuilt the AC system on this 1995 Chevy truck. The only original parts are the evaporator and the bottom line going from it to the condenser. I flushed these both with a full can of flush, blew out with dry air for :mad:at least an hour. It's all new, Condenser, even main hose, Delphi R4 style compressor, of course new accumulator and orifice tube. I don't monkey around with questionable parts!
Before bolting hose onto compressor, I added 2.5 oz PAG-150 (per manufacturer and dealer) to compressor input port, and 5.5oz balance of 8oz bottle PAG to receiver/dryer. I connected everything, drew a vacuum to about 29.5 inches (or better. it's a very serious 1hp vacuum pump..) It held for an hour, so I ran vacuum pump again to evacuate for 45 minutes.
As I added the first can of R134a, I started engine, AC on high/fan hi, and got about 80% of "first can" into system when low pressure side began climbing fairly quickly (1 to 2 minutes.. 30psi, 40, then 50, then 75.. Compressor was cycling off and on and was loud, then began to strain the engine.. the hi side went to about 400 psi!! ..so I shut it down out of fear of the can exploding in my hand! With everything turned off, pressure equalized (both sides) to about 80 psi! I disconnected the can for fear of it exploding!
I am stumped. No matter what I do, the pressure on both sides was wildly high. So, I bled off some of the pressure, got it so high side is about normal (300psi) but low is still at 60+ when running: but mind you, it's less than one 12oz can of charge! Not getting cold at all. Adding more R134 will surely only increase both sides again, right? This is a simple A/C system, no fancy controls other than 3 pressure switches, which all seem to have activated at one time or another, cutting power to the clutch intermittently. The condenser never got significantly hot either.. so not a shortage of airflow up front..
I suspect I either have too much oil in the wrong place, got liquid R134a into the system (I did not need to move the can much, as some people do.. as it is very hot here, a bit over 100F outside temp..)
I've never had a problem like this. Any suggestions will be appreciated. For now I have had to move onto other things, so I thought I'd post this and see if I am doing something stupid.
I completely rebuilt the AC system on this 1995 Chevy truck. The only original parts are the evaporator and the bottom line going from it to the condenser. I flushed these both with a full can of flush, blew out with dry air for :mad:at least an hour. It's all new, Condenser, even main hose, Delphi R4 style compressor, of course new accumulator and orifice tube. I don't monkey around with questionable parts!
Before bolting hose onto compressor, I added 2.5 oz PAG-150 (per manufacturer and dealer) to compressor input port, and 5.5oz balance of 8oz bottle PAG to receiver/dryer. I connected everything, drew a vacuum to about 29.5 inches (or better. it's a very serious 1hp vacuum pump..) It held for an hour, so I ran vacuum pump again to evacuate for 45 minutes.
As I added the first can of R134a, I started engine, AC on high/fan hi, and got about 80% of "first can" into system when low pressure side began climbing fairly quickly (1 to 2 minutes.. 30psi, 40, then 50, then 75.. Compressor was cycling off and on and was loud, then began to strain the engine.. the hi side went to about 400 psi!! ..so I shut it down out of fear of the can exploding in my hand! With everything turned off, pressure equalized (both sides) to about 80 psi! I disconnected the can for fear of it exploding!
I am stumped. No matter what I do, the pressure on both sides was wildly high. So, I bled off some of the pressure, got it so high side is about normal (300psi) but low is still at 60+ when running: but mind you, it's less than one 12oz can of charge! Not getting cold at all. Adding more R134 will surely only increase both sides again, right? This is a simple A/C system, no fancy controls other than 3 pressure switches, which all seem to have activated at one time or another, cutting power to the clutch intermittently. The condenser never got significantly hot either.. so not a shortage of airflow up front..
I suspect I either have too much oil in the wrong place, got liquid R134a into the system (I did not need to move the can much, as some people do.. as it is very hot here, a bit over 100F outside temp..)
I've never had a problem like this. Any suggestions will be appreciated. For now I have had to move onto other things, so I thought I'd post this and see if I am doing something stupid.