MACS Monthly Newsletter - 2020 - FEB8

A/C CUTS OUT
Sometimes the A/C operates normally when first
turned on, seems okay for a brief period of time,
then cuts out. Turn it off and on again, and it cools
briefly once more. There are probably a dozen or
more possibilities. And the vehicle in this case is a
2001 F-350, so it's about 19 years old with an odometer reading approaching 200K.
The diagnostic thoughts usually are in the area
of well, it's old, has the original compressor, so unless there's an obviously bad connection at one of
the switches in the circuit, let's just put on a new
compressor. Well, the wiring pigtail on the highpressure cutout switch had been replaced not long
ago, the low and high-side pressures both are in
the normal range and the system hasn't been leaking, was recharged some years ago and a recovery/
recycle/recharge machine checkout shows it has a
full charge.
How about the clutch gap? Bingo. It's 0.038-inch,
which is measurably above the spec of 0.014-0.030
inch (Figure 11).
The technician removes the hub and finds the
clutch facings shows signs of wear but basically are
in good condition. However, there's just one shim,
which he carefully measures and finds it's 0.030inch. Reassembly with that shim left out would
reduce the gap to 0.008-inch, which is BELOW the
0.014-inch minimum spec. Quick phone calls confirm there are no shims readily available, and a new
clutch kit will take 1-2 days to obtain. The customer
needs his truck now. So, the technician reassembles
the clutch and finds that the A/C performs normally - no cutting out.
Is this how the story should end? The correct answer is no. When the gap is below the minimum
spec, the clutch may not release properly, and if the

motorcraftservice.com

compressor runs hot as a result, the nose bearing
lubricant could melt and then the vehicle owner
will face a bigger ticket than for a clutch. The technician has these reasonable choices: (1) just warn
the motorist of the likely consequences, including
compressor failure, and write them on the job ticket; (2) tell the motorist that a new clutch has to be
installed and he will leave the clutch coil disconnected, so the A/C is inoperative and to bring the
truck back in a couple of days for a clutch installation; (3) connect the coil so the A/C is operative if
the motorist insists, but have him agree to a clutch
kit and a service appointment. Order the kit and if
possible, get a deposit on the parts. n

Figure 11: Ford F-350 compressor clutch gap should be
between 0.014-0.030-inch. With shim removed however,
it's only 0.008-inch.

MACS Service Reports is published monthly by the Mobile Air Conditioning Society
Worldwide. It is distributed to members of MACS Worldwide and is intended for
the educational use of members of the automotive air conditioning service and
repair industry. Suggestions for articles will be considered for publication, however,
MACS Worldwide reserves the right to choose and edit all submissions.

Editors:
Elvis Hoffpauir, Steve Schaeber
Production Designer:
Laina Forcey
Manager of Service Training:
Steve Schaeber
Mobile Air Conditioning Society Worldwide
P.O. Box 88, Lansdale, PA 19446
Phone: (215) 631-7020 * Fax: (215) 631-7017
Email: membership@macsw.org * Website: www.macsw.org

Unless otherwise noted, all photos/art by author.

February 2020

MACS Service Reports

http://www.motorcraftservice.com http://www.macsw.org

MACS Monthly Newsletter - 2020

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