Automotive Air Conditioning Information Forum (Archives)

RockyMtnMan on Mon July 04, 2011 6:07 PM

Year: 1991
Make: GMC
Model: Suburban
Engine Size: 5.7l
Refrigerant Type: R134a
Country of Origin: United States

I got this GMC Suburban (V2500 with 350) about 10 years ago, and it came to me with a marbles
rattling compressor, dual A/C with R12. The owner had recharged the A/C the previous week,
but it had already leaked out by the time I test drove it (and doomed myself to it).

My then-mechanic in CA said it was a good time to convert to R134, since the compressor was
getting swapped out for a new unit; he did a minimal flush job (probably didn't pull the expansion
valve in back, nor the oriffice tube in front), and the resulting A/C performance was underwhelming.

He did screw on the retrofit charging adapters; is that a reversible change?

A few weeks later, the charge had leaked out, and he swapped out the larger of the two rear
A/C lines for a fresh factory hose; he did not change O-rings elsewhere, nor convert to "barrier"
hoses. Now the 'Burb will hold a charge for about a summer, so there's either a very slow leak
somewhere, or I'm dealing with porous hoses, or some other gotcha. I have the system
discharged now (rear motor fan is shot), so I could dig in and do some serious flushing,
then recharge with R134a and look for leaks.

Questions for the forum:

Does this seem like a reasonable plan? I'm wondering if the conversion simply wasn't done to the
standards recommended by this forum (especially the flushing). Maybe I should replace the stock
hoses with "barrier hoses" and replace all O-rings on principle, are these even available for a vehicle
this old (aside from a custom hose fabrication effort)?

Should I consider converting back to R12? Seems these 'Big as a House' vehicles don't do well with
the retrofit. I'd want to be sure I was leak-free before taking the $$$ plunge. I'm very happy with my
other vehicles I've left at R12 (1983 Mercedes, 1987 Shelby CSX).

Should I convert to a parallel flow condensor? Even with R12, my older Big Block Suburban didn't do
well at idle, even after I replaced the fan clutch.

Any pointers to a GOOD A/C shop in the Denver/Boulder area of Colorado?

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'91 Suburban with dueling AC

TRB on Mon July 04, 2011 7:33 PM

Max-Air in Denver has been around a while.

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When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

chris142 on Thu July 07, 2011 12:11 AM

I've had no luck with making an older Suburban work on R134a. They just wont work. The thing is going to hold 5.25 lbs of R12 though.