Just started having some strange problems with my AC in a 1990 Miata. It will be running fine then the idle goes up to around 2000 and no cold air. Dose this for a few minutes, maybe 5-10, then comes back. Is it low on freon or some other issue. Thanks.
I'd look for a bad relay.
My a/c has just decided to stop working altogether (haven't used it all winter and only tried turning it on for the first time yesterday). When turning it on the idle speed goes up BUT the engine doesn't lose any power the way it used to do when the a/c came on. No cold air at all. Should I look in the same place - the relay - or is it likely to be the coolant?
Eric
I believe that there is a low pressure limit sensor that is tripping. This is usually because of low freon. Or, if a high side sensor is present, high pressure. (I don't remember what was used on a 90.) This can also happen on many cars if the cooling coil gets too cold. The high Idle says that the A/C is told to turn on. You may find that the additional cooling fan is also running. The behavior you mention is actually sort of normal for a 90 Mazda MPV van. (As long as the A/C cools the van properly)
Most likely low freon or a compressor problem. Does the compressor clutch engage?
How would I know whether the compressor clutch engages?
Eric
"Eric Baber" wrote in news: snipped-for-privacy@individual.net:
You should be able to see it. It's tucked away where it's not as easy to see as some cars but it is visible. When the compressor is not engaged, the outer part of the pulley turns but the center part doesn't. Turn the AC off and take a look, then turn the AC on and you should see the center part of the compressor pulley turning with the outer part.
Is there a way to test this high side relay?? Checked the freon and it looks like the proper amount, going by the site glass.
Mac
Witht the A/C on and cycling, you should see some bubbles. This is normal. If there are no bubbles, or an excessive amount of bubbles(foam) the charge is respectively too high or too low. A worn compressor can also cause an abnormal bubble appearance. Since this is a 90, it's really past time to hang a set of gauges on it, and see whats going on. If this is (As I suspect) a car with the classic freon in it (not 134a), the freon is expensive.
Some of the things that can cause cycling-- Low or high freon pressures (depends on type of sensors installed) Clogged evaporator orfices Clogged filter A worn compressor does not normally cause cycling. In forty or so years, I did run across one A/C clutch that intermittently kicked off, and caused a compressor to cycle. (The clutch coil was opening when it got hot, cooled off, and would then work for a few minutes, and repeat the cycle.)
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