I have a question about the a/c on our 1997 Mercury Tracer. When we
started using the a/c this year, we noticed that the air wasn't as cold
as it normally is. We also noticed that the idle of our car would flip
back and forth when we would have the a/c on and were stopped at a
traffic light. So, we took our Tracer in and were told that it needed
freon and the compressor would need to be replaced relatively soon.
They added freon and the a/c works great. Also, the idle flip doesn't
happen anymore, but there have been issues lately with a weak idle when
the a/c is not on. Here is my question. Would an air
compressor/clutch affect the idle or performance of an engine if the
a/c is not on and the compressor has not locked? I'm asking this
because it would cost us approximately $700.00 to replace the
compressor and I'm worried about getting our car back from the shop and
having a more urgent problem. Any information would be greatly
The idle w/o the a/c being on has nothing to do with the compressor,
unless it's making a terrible screaming noise because it's about to
seize up. You probably need to look at one of the standard things
that go wrong with these engines as they age: spark plugs, plug
wires, idle air control valve, pcv valve, pcv/vacuum hose leaks.
The engine computer is designed to increase the idle speed when
the a/c is on, which masks the idle problem you have. A low a/c
refrigerant charge means the compressor will cycle on and off
more frequently, because the low pressure cut-off is reached
more often (low side pressure drops when the compressor is
running, and rises again when it cycles off).
Also, R-134 (not freon) costs less than US$10 a can (don't use the
stuff with stop leak, ever!), and if this recharge lasts a month or two,
you can buy an awful lot cans for $700. I'd continue recharge the
system as needed (at least once a year, as often as once a month)
until the compressor actually needs to be replaced. You can actually
buy a recharge hose & gauge and learn to fill it yourself fairly easily.
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