I have the carb model 5 speed. The AC light comes on in the dash, but the
compressor doesn't turn on. I traced wires and when I checked for power to
the compressor, it ran when the test light probe touched the wire. It also
works by direct power to it. I assume there are relays for it. I also
noticed a switch on the line, assuming it's for low coolant pressure. My
question is, will low coolant prevent the compressor from activating? I
need to switch it over to 134, but don't want to waste time and coolant
until I trace the problem down. My repair manual doesn't mention anything
about this other than taking it to a qualified technician...
Thanks for your help.
Ah, I love those cop-outs in the manuals. The funny thing is that there is
often some troubleshooting you can do yourself.
I'd definitely check out the low pressure cutout switch. Usually you will
get a long period of excessive compressor cycling before it refuses to work
at all, but a large leak or a long time without using the A/C can skip you
past that. Anyway, pull the connector off the switch (with the engine off)
and measure the switch. It should have continuity. Alternatively, you can
put a jumper in the connector to see if the compressor pulls in (engine and
A/C on), but don't do that for more than a moment to avoid damage to the
compressor... or replace the compressor connection with your test light.
I am ambivalent about R-134a conversions. R-12 is outrageously expensive
these days, but converted systems just don't work as well as unconverted
systems of either type.
Either way, if the pressure switch is what is holding the compressor off you
will need to go to a pro - either to get the R-12 charge (you can't buy the
stuff) or for a proper conversion. If it's not the problem, come on back and
we can go deeper.
I found and jumped the low pressure switch and it seemed to work. I did the
134 conversion myself with new o-rings, oil, and the refrigerant. Cooled to
48 degrees. It could probably take another small can, but it's working. At
least for now. Leaks may show in a day or so...
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