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?
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
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)
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
Some of the things that can cause cycling--
Low or high freon pressures (depends on type of sensors installed)
Clogged evaporator orfices
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.)
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.