Climate Control
A/C Compressor Runs Constantly
Symptom: Regardless of whether the "AC" switch is pressed in or not, the A/C compress runs
constantly.
>> The only time I don't have power to the compressor is when I have the selector
>> switch on the heater control to "off". At all other times the compressor turns.
>> I should mention that I have a manual system. When I press the "AC" switch,
>> the light comes on but as far as I can see it makes no difference whatsoever
>> since there is always power going to the compressor.
The only things that will cause the compressor to stay on are the relay (if it's stuck closed) or
the dash panel AC switch if it's holding the relay closed. The AC switch has two contacts-- one
pair goes to the relay, while the other illuminates the lamp within the switch itself. The switch
on my car is part of a panel between the the controller and the radio. There's a reset switch for
the electronic display (not a problem for pre-'89 cars), and the central lock button. The AC
switch has its own little plug-in connector, and can be easily checked with a meter after it is
loosed but not removed from the dash. If the switch is bad, replacement of the little panel
assembly is the only practical solution. Give 928 Int'l or David Roberts a call to get the part you
need.
The relay has two contacts also, which can be checked by removing the controller and the
covers. The relay itself is that little [blue on my car] cube on the controller, about 13mm wide,
20mm long, maybe 10mm thick on the board. The contacts are screened on the cover, so it's
just a matter of tracing a few connections with the ohmmemter to find if it's stuck. If it is stuck
and you don't want to play electrical surgeon, I'm sure replacement controllers are available
from Mark or David. I found the substitute relay at a store just minutes from 928 Int'l. I figured
that if I buggered the old unit I have a fallback local to me; you may not have that option so
handy, so getting a replacement controller may be the best option for you.