A.c. compressor


Asked by Jun 11, 2017 at 10:02 AM about the 1997 Ford F-350 2 Dr XLT 4WD Standard Cab LB

Question type: Maintenance & Repair

The a.c. compressor in my truck is continuously
engaging and disengaging while the a.c. is turned
on. The a.c. that is blowing is not cold. My initial
thought was to buy a.c. pro, check the pressure,
and add that to the system to achieve cold a.c.
Once I realized that the a.c. compressor was
turning on and off repeatedly (every few seconds) I
decided NOT to add the a.c. pro just yet. When I
hooked up the gauge to the low side hose the
reading was normal when the a.c. compressor was
turning and very low when not turning. I've read a
million forums on this problem but cannot seem to
find a general answer to it. Summer is coming and
I would just like to have cold a.c. for those 100+
degree days. Any idea on steps to Take? Is it safe
to add the a.c. pro? I know too much is a bad

1 Answer


Your high and low pressure readings will vary due to ambient temperature. Mastercool has a download chart so there is no guesswork. You will need a manifold set to do this properly. They can be rented sometimes or just buy one. I suspect you might have more than one issue due to the age of the vehicle such as a leak, clog, and most likely low on freon. Not a big fan of leak dye but sometimes it's necessary to pinpoint a problem. On older compressors a common issue is that the center shaft O-ring develops a leak which can be tough to diagnose if it's in a early stage of failure. On many fords there also is an inline filter called an oriface tube that can get clogged up over time. This would require capturing the freon and pumping down with a suitable vacuum pump. Other items to replace during this time is the receiver drier. If there is a leak and you don't find it you will be back in there again. Good Luck!

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