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1979-1993 & 94 Conv [Subscribe to Daily Digest] |
David,
Here are a few things to look at to narrow down the possibilities:
1) Freon low. Steady, slow leak somewhere in the system has depleted the freon, causing the A/C low pressure switch to keep the a/c compressor clutch from engaging. This will probably take a skilled a/c mechanic to find leak (special dye treated refrigerant to trace leak, I believe) and fix.
To test for freon loss being culprit, you simply (temporarily) bridge the low pressure switch wires together, then push the a/c dash button on. This is located on the receiver/dryer, which has the sight glass in the top of it (it's next to the washer fluid bottle under passenger side of hood in fenderwell). If compressor kicks in with wires bridged, then freon is low, and you've got a leak to find & fix. I'll try to post my photo of switch & receiver/dryer below.
2) Anti-frost switch faulty. This thermostatic switch cycles the a/c compressor off when the temperature of the cooling coils (evaporator?) which air going to the cabin passes through to be cooled reaches 38 degrees F or so. It keeps the coils from icing over, which would happen, especially in humid weather, effectively blocking the airflow into the cabin. (This switch can go bad one of 2 ways: "stuck off," where the a/c never cycles off and coils may ice over; or "stuck on," in which the a/c compressor will not turn on--a possibility for you.
I had the "stuck on" problem with my previous 900. I never knew clutch on compressor was supposed to cycle on the 900s until I asked my mechanic once. He told me the anti-frost switch was the culprit and I had the better of its two "deaths," i.e. being able to use the A/C!
3) Compressor clutch faulty. (I don't know how to test that).
4) A/C relay faulty. (See below link to Swedish Wrench website.)
5) Dash switch faulty. (Ditto.)
For more information on testing the a/c system, I suggest the Swedish Wrench website. I'll link to it below.
Hope this helps!
Micah in NC
'84 900S, 214K mi.
'90 900, 65K mi. (Mom's)
posted by 216.77.233...
Click here for A/C diagnosis page on Swedish Wrench site.
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