MACS Service Reports - 2016 - SEP2

A/C Compressor and Clutch Assembly

The compressor is the other big one. We've gotten away
from doing much in the area of shaft seal replacement.
Clutch replacement is for when you can do the job on the
car, and when you replace the compressor, you often have
to change over switches to a new compressor. But as we've
noted in the May 2015 edition, there are two additional jobs
you likely can do, often on car: replacing an external solenoid valve after testing with one of the new control valve testers, or replacing the General Motors V5/V7 internal control
valve after a performance/pressure test.
And if you're lucky, here are two others we came across:
One is the HU6 axial six-cylinder compressor's high-pressure
cutout switch on 2003-05 Chevy and GMC vans and 2000-02
3500 series trucks. The switch was available as a detail part at
one time, but on vehicles more than 10 years old, not so much
anymore unless you find one on a dusty shelf at the dealership.
However, Four Seasons still offers a replacement for ones with
the purple or orange plastic housing, as Part No. 20055. (Fig. 2)

NOTE: Internal A/C compressor components are not serviced separately. The variable scroll compressor is serviced
only as an assembly. The A/C clutch, A/C clutch pulley and
the A/C clutch field coil are serviceable.
The variable scroll A/C compressor has the following
characteristics:
* A variable capacity function controlled by a suction pressure sensing device.
* A fixed and orbiting scroll to provide refrigerant
compression.
* A non-serviceable shaft seal.
* The A/C compressor uses PAG Refrigerant
Compressor Oil YN-12-D WSH-M1C231-B. This
oil contains special additives necessary for the
A/C compressor.
The A/C compressor contains a thermal cutout
switch which senses the compressor housing temperature. The switch will disengage the A/C compressor
clutch if the housing temperature exceeds 120°C (247°F).

Four Seasons

However, there are remanufacturers selling "reman" scrolls.
Okay, we recognize that if there's damage to a bearing that results in contact between the fixed and orbiting scrolls that the
compressor core may not be worth salvaging.
However, notice that the Sanden variable scroll has a "suction
pressure sensing device." That's the control valve and it can be
replaced. Ford doesn't supply it, but you can order it from Santech (santech.com) and one technician found it on the Autozone
site (it's on other sites too) and was able to pick it up at an Autozone store. Part No. is MT2270. (Fig. 3)
The thermal cutout switch is used on many scrolls and it's in
the compressor clutch circuit, although you usually will not see
it called out separately. If it opens (at above 247 degrees F.), the
compressor is probably trash, but we've heard some remanufacturers have found cases where the switch itself failed, so they can
salvage the compressor itself.
We've long been surprised that the thermal switch is not available as a detail part, but the compressor manufacturers seem to
feel (and they probably know) that the failure rate is so low that
when a thermal switch opens, it's an internal compressor issue
and they want the compressor
replaced.
That thermal switch does
take some time to open in many
cases. Example from a 2006
Honda Civic: turn on the A/C,
system blows cold air briefly,
then stops. Fans even stop. Turn
off the A/C, wait a few minutes
and try again. Same problem.
This is often mistaken for an
Figure 3: New control valve for
evaporator temperature sena range of Sanden variable output scroll compressors is availsor issue, or even an outside air
able to correct many poor cooling
temperature sensor, but if it's a
problems, available from Santech
scroll it surely has that switch
and also found by technicians at
and if you can bypass it for a
Autozone stores, among other
outlets.
test, that should confirm it. ■

Figure 2: Switch in back head of HU-6 General Motors compressor is available
as a detail part from Four Seasons.

September 2016

Santech

Second is the Sanden variable-output scroll used on a
range of Ford products from 2000-2008, primarily the Ford
500, Mercury Montego, Ford Freestyle, Jaguar S-type, Jaguar
X-type, Lincoln LS (a Jaguar S-type twin) and some Chevy
Equinox.
A variable output scroll compressor is one with a bypass
valve that controls output according to engine rpm and basic
cooling load. In that respect it does what the internal control
valve does on a V5/V7 compressor, except there's no swashplate and pistons to make displacement changes. As a result,
the output control is only modestly effective at improving
efficiency in a scroll. Truth be told, the internal control valve
isn't all that much better on a piston compressor. Which is
why many piston compressors have externally-regulated
solenoid valves and scrolls are most efficiently controlled
where powered by electric motors, as in hybrids and electric
vehicles.
It is not uncommon for that scroll compressor valve to
stick and create a poor/no cooling condition. However, OE
suppliers, both at the car maker level and at their suppliers,
have never recommended any service of a scroll compressor
beyond replacement of a clutch assembly or the pressure relief valve if it's part of the compressor. Here's a direct quote
from the Ford service information system (www.motorcraftservice.com).

MACS Service Reports

http://www.santech.com http://www.motor http://www.craftservice.com

Table of Contents for the Digital Edition of MACS Service Reports - 2016