Re: O/T 93 Suburban a/c problem

Posted by jdemaris on October 12, 2005 at 05:49:43 from (66.218.24.171):

In Reply to: O/T 93 Suburban a/c problem posted by Gene Davis (Ga.) on October 11, 2005 at 19:33:09:

The frequent cycling is usually an indication of a slow leak and being low on refrigerant. If you temporarily put a jumper-wire on the harness connector to the low-pressure switch, it will probably smooth out. This switch has a screw-slot in it and can be adjusted also. That won't fix a low gas pressure situtation, though. I've got several Suburbans (87, 99, and 91) and I had to convert them all to 134A. It works fine.
Keep a few things in mind. First, many Suburbans have rear AC as well as front, and the long aluminum lines that run front to rear tend to spring leaks where they are clamped. That is caused by GM using steel clamps against aluminum lines which causes an electrolytic reaction (like battery corroision). I've replaced all of mine with rubber AC hoses - but I live in central NY in the rust-belt. Maybe you don't have that problem.
Also keep in mind that AC hoses made for older R12 systems are not suitable for 134A. The molecular structure of 134A is smaller than that of R12 which enables it to pass though the older type rubber AC hoses very slowly, but surely. That's why they were all changed to "barrier" hoses now. The newer hoses have a plastic liner inside of them, thus the name "barrier."
The GM system you have is prone to orifice-tube plugging. You should inspect your system for leaks - you might see it by the presence of oil by a trouble spot. You can also use a professional leak detector (if you have access to one), or, make an adaptor and hook compressed air to your system and listen for leaks. Chances are though, in your case, you've got a very slow leak. Once you find your leak or leaks, and the system is empty, pull the orifice tube and check it - it usually has trash on it. If you have rear AC, the rear unit also needs to come apart for cleaning.

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