MACS Service Reports - 2015 - OCT7

THERE'S ALWAYS ANOTHER CAUSE: COMPRESSOR CLUTCH
no refrigerant in the system, so there's apparently a leak. The system is recharged, with trace dye added. The system then works
for a couple of days, then stops. Must be a big leak, right? The
A/C specialist has a new R/R/R machine, so he does a diagnostic-intent recovery. The system may have had a leak, but no
sign of one now, as the machine pulls out a full charge, and puts
it right back in. All the fuses are good, there's a 12-volt reading
at the clutch coil and the test light goes on to indicate a good
ground. The technician replaces the clutch relay, which is a common cause of intermittent operation To no real surprise, following the recharge, the system starts working again.
The technician next checks the clutch air gap. We've encountered lots of these and it doesn't take much for a clutch gap that's
borderline to cause an intermittent. It's .020" and the OE spec is
.014" - .026" which is just at the midpoint.
Next, a perusal of the wiring diagram (Figure 12) raises the
possibility of the thermal switch being defective. The technician
tries a wiggle test on the harness and nothing seems to be indicated. This is one of the few thermal switches that not only
is replaceable (Figure 13), but to an extent is serviceable. So the
technician removes it and although it looks okay, and the compressor body had not been running unusually warm, he replac

techinfo.honda.com

So long as there's a compressor with a clutch, we suspect there
will be new causes of clutch misbehavior. Sure, we'll still have
most of the familiar ones, and sometimes we'll put so-called new
causes into familiar categories. Perhaps the always something
new area is caused by the fact that manufacturers keep revising
the wiring circuits. So long as the electrical/electronic architectures are updated, why would you expect only the same old
stuff?
Intermittents are naturally the toughest ones, because you
have to be able to duplicate the problem, and that isn't always
easy. Circuits won't always cooperate.
This time we're looking at a not so new car; a 2007 Honda
Civic with the 1.8-liter four cylinder. A pretty basic car, probably
a pretty familiar system, or so you might think.
What makes this less common is that it came from another repair shop; not an A/C shop, but still one that can be expected to
provide reliable information. It comes into the specialist's place
with a report that even when it stops working, the radiator-condenser fans are spinning, and apparently at normal speed.
However, at the time of arrival, nothing was working. There's

techinfo.honda.com

Figure 13: Thermal switch is held in compressor by retaining bracket with
screw.

Figure 14: If the thermal switch must be replaced, apply a dollop of silicone
grease to the base of the new switch, then spread.

Figure 12: Honda Civic wiring diagram shows use of thermal switch in
clutch circuit.

October 2015

MACS Service Reports

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Table of Contents for the Digital Edition of MACS Service Reports - 2015