A/C conversion

Year: 1993
Make: Chevy
Model: Suburban K-1500
Engine Size: 350 in3
Mileage: 235k
Location: Albuquerque, New Mexico
A/C System: Dual A/C, R-4 compressor
Capacity: 5.25 lbs.
Refrigerant: was OEM R-12


I’ve had this Suburban for years, bought it when only 3 years old with 110k of highway miles on it. It has been absolutely trouble free for me. Only problem was an A/C compressor at 180k miles (~6 years ago). I carefully flushed the system and replaced the compressor myself at that time and the A/C worked great ever since. Last winter I crumpled the right front corner (talking on a cell phone - I learned my lesson, now it goes unanswered if I am driving). I replaced the front bumper & supports, the inner and outer front fender and the radiator support, which were the only parts that got bent (had the frame checked at a frame shop). During my repair, I cut a slot to the hole where the condenser tubes went thru the radiator support so I would not have to crack the A/C system (I’m a DIY guy so I don’t have recycling equipment) Had to manipulate the condenser around quite a bit to free it while replacing the radiator support. This spring, the A/C didn’t work. A quick check showed no refrigerant left in the system. I suspect the manipulating the condenser opened a small leak in a connection. I am now faced with fixing the system and I am planning on converting from R-12 to R-134a because of the cost and/or non-availability of R-12. I’ve read lots of articles on converting, ranging from “just put in R-134a and go” to “don’t, you’ll be sorry”. I am a mechanical engineer by trade, so I understand the issues. I plan on thoroughly flushing all the lines and components I can to clear the old oil along with bench flushing the R-4 compressor with new oil. The system was the last year GM used R-12 so the replacement compressor (~ 6 yrs. old) should have compatible seals. The only new parts I plan on installing are new joint seals all around and of course, a new receiver dryer and conversion fittings. Does anybody have any experience with this setup in a ‘93? Are the OEM hoses the barrier type? The condenser is a serpentine fin and tube, which I understand is not ideal for R-134a. Would it be worth the effort and expense to replace the condenser with a parallel tube? I am unemployed right now, so $$ is tight and labor is cheap. I don’t want to spend any more than absolutely necessary. Is there anything else, low cost, I am overlooking that will improve my system? I have a factory service manual which gives the oil capacity of each component separately so I will distribute the new oil during reassembly. In another vein, flushing agents seem to be a bit expensive, does anybody know what they consist of and is there a low cost substitute? I have a really good Welch vacuum pump capable of pulling a base pressure of 10-20 millitorr, so I can suck almost any solvent and all the water clear of the system if I leave the vacuum pump on for a long time.

Thanks in advance for any advice or tips,

Timelord

True, R4 is not a great compressor, especially with a dual-AC system like in most Suburbans. My 994 Sub was sold last year at about 220K miles, went through about 4 of those. Now, my '94 was factory R134a though, and did cool well. As to your issue, it will be easier and cheaper to actually stay R-12, then you don't need to guess about trying to flush everything including refrigeration oil. R-12 is legal in US, and available, there are just few shops which still have the equipment, so you'll need to do yourself. See ackits.com for stuff, and you can get loaner vacuum pump at AutoZone which will have fittings for both. To legally buy R-12, get an online 609 certificate, and also see Ebay.

Unfortunately your system has a large refrigerant capacity.