MACS Service Reports - 2016 - JUN8

tional orifice tube, so for most shops the "by the book" and the
practical field fix are the same -- new OE liquid line.
The inlet end of the VOV has the nylon mesh filter screen,
which filters the refrigerant and helps to reduce the potential
for blockage of the metering orifices by refrigerant system contaminants. The outlet end of the tube has a nylon mesh diffuser
screen. The O-rings on the plastic body of the VOV seal the tube
to the inside of the liquid line and prevent the refrigerant from
bypassing the fixed metering orifices. A thermostatic bimetal
coil wrapped around the valve body serves as a refrigerant flow
regulator for the variable orifice during temperature changes.
The VOV varies the flow of refrigerant in response to the refrigerant temperature exiting the condenser. As condenser discharge refrigerant temperature increases, the variable port is
progressively closed. A higher temperature (while idling) equals
more restriction. A lower temperature (at road speed) will have
less restriction. There's a diffuser screen at the outlet of the two
orifices.
There is no standard diagnostic for a VOV with a non-responsive variable orifice. But if the complaint is that the cooling is
normal except at hot idle or in very hot ambients (typically over
100 F), that's when the VOV is suspect.
The VOV was used on a number of Chrysler products
through the mid-2000s, with the PT Cruiser among the highvolume applications.

agnosis and saw no cooling improvement, but there were other
problem areas that had to be solved first, and now that they
were, he could return to that check, which seemed to be a promising one-- what else was left? He operated the HVAC controls
and could both see some movement and hear the doors moving. But he couldn't definitely determine how the blend-air door
was moving, and when he decided it had to be the issue, he
expended the effort for a definitive answer. The door indeed
was moving, but not all the way and the fix was a new blend-air
door assembly, which Chrysler has long supplied as a repair section. You do have to remove the heater-A/C housing from the
vehicle, but the blend-air door section is held by just two screws
and is easily removed for replacement. The new section goes in
nicely - just be sure to align the door pivot pins with the pivot
holes in the housing. FIG. 16.
Although replacing the recirc door vacuum actuator is a major job that requires removing the instrument panel, the temperature (blend-air) door actuator (used on both manual and ATC
systems) isn't so tough. Once the under-dash surround panel
and glovebox are out, and the harness unplugged, you can get
the door motor (two screws). The mode actuator is tougher -
center instrument panel support bracket has to come out. However, if the problem is with the door assembly and you have to
install a blend-air door section, the heater-A/C housing has to
come out -- bigger job, but that was what was called for in this
case.
A new section was installed and the A/C register temperatures got down into the 40's F. Job done. ■

Now back to the cooling problem

techauthority.com

The technician sold orifice tube inspection (some debris) and
following that a new receiver-dryer. Still poor A/C cooling.
So the technician charged the system to specifications and
very prudently installed a dose of trace dye. This is sound procedure on new systems of course, which have oil separators that
minimize the amount of oil in circulation for energy conservation. But it's even more important on very old systems where
you can't find a leak, hope that the refrigerant loss is normal
but really can't be totally sure. This way if you've missed a rubthrough in a hard-to-check location, or wherever a leak may be
hiding, a dye trace may help you if the car comes back.
Unfortunately although the cooling was better, it still was subpar and the gauge readings were high (67 psi low side, 250 psi
high side). Still some debris in the system? Likely, so the technician flushed the system and the pressures came down to 47 psi
and 210 psi. For the ambient, that seemed okay, but the cooling
still wasn't good enough -- A/C register temperatures around
60 F.
What now? He could recheck the charge, but the recycling
machine was new and had recently passed a scale calibration
check.
The technician had pinched the heater hoses early in his di-

Figure 16: This blend-air (temperature) door assembly is supplied by
Chrysler as a repair section. Although it's held by just two screws that
hold it to the heater-A/C housing, you do have to remove the housing to
install it.

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.

June 2016

MACS Service Reports

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

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