MACS Monthly Newsletter - 2019 - FEB2

Dave Hobbs
Dave Hobbs

Figures 1 and 2: CPS supplies a set of Bluetooth, battery powered thermometers that pair to your smart phone (iOS or Android) to read out temperatures via a non-contact method. Simply extend the head from the rubber coated, spring loaded clip
to turn the units on. Blue LEDs will flash telling you the units are active and the batteries in each are good.

A Word on Variable Displacement Compressors & Test
Equipment

Figure 3: The CPS
Bluetooth
thermometers display right on
your phone. Advanced
information such as humidity and dew point
are included, as are options to store files on
your phone in order to
review or share with
customers. More than
two thermometers can
be linked to your smart
phone. Simply pair and
scroll down to review
the temperatures you
are measuring. In this
photo, my TS-100 Blue
is in the center dash outlet and the TS-100 Red
is out in front on the grill. No complaints with the vehicle
(2018 Ford Escape) cooling on a moderate day, even though
the classic ambient to center duct temp drop of 30°F is not
achieved. If it's not broke . . . don't fix it!

eVDCs (electronically controlled variable displacement compressors) have been around for many years
and are not going away any time soon. While some
scan tools allow you to activate the compressor's solenoid to observe for a change in both test port pressures
with your manifold gauge set / RRR machine, there are
many others that do not. This includes some OEM scan
tools such as the Ford IDS.
* Techno Tools - For this reason Ford has even opted
to purchase an aftermarket tool from Techno Tools
(Figure 4) that has a connector designed just for Ford
compressors. Considering the current factory procedure (Ford pin point test) where you watch for a pressure change while moving the temp controls from
cold to hot, this was a smart move by Ford to pick
up this tool for their dealers. The tool plugs into the
compressor and the vehicle harness to allow for the
vehicle to do normal solenoid control or allow you to
control the solenoid while watching the gauges.
* Four Seasons is marketing a universal eVDC tester
(Figure 5) with a bunch of popular adapters that plug
into the more common connectors out there. Find the
correct pigtail for both the compressor and the vehicle
harness that you're working on, and you can not only
avoid setting a DTC by disconnecting the compressor's solenoid, you can also test the solenoid's resistance, allow the vehicle to do its own thing, or manually run the variable displacement duty cycle up and
down while watching gauge pressures react. The tool
appears to be similar to the unit also marketed by
GPD (Global Parts Distributors).
* AirSept has been an innovative technology leader
in just about anything A/C related for decades. Their
latest variable displacement compressor solenoid tester (EVC-2 w/temperature sensor) goes above and
beyond the call of duty by allowing you to do everything the other tools do PLUS monitor temperatures
on both the high side and low side (Figure 6). Since going beyond the gauges is what we are talking about,
this makes a ton of sense. On the down side you have
universal leads (alligator clips that you'll then need
to connect to your own male and female test terminal
collection). My Murphy's Law experience has proven
that no matter how many connectors a tool maker

Updated Findings: Temp Drops at Bulkhead Inlet / Outlet
Evaporator inlet / outlet access? Which vehicles have
accessible evaporator inlet AND outlet lines today? A very
large portion of late model vehicles have an H-Block style
expansion valve mounted right at the bulkhead where the
refrigerant lines go into the passenger's compartment to
connect to the evaporator core. Therefore, the high side of
the system will be on the line going into the expansion valve
and the low side coming out of the expansion valve. This
means the only way you could truly even get to the inlet of
the evaporator core is to access the evaporator case inside
the vehicle, which of course is much easier said than done.
* TXV Inlet vs. Outlet Observations
* 100°F diﬀerences are quite common when
measuring the two lines entering the TXV.
* 30°F diﬀerences are quite common when measuring the two lines entering the TXV.
* What makes the variation so high? Three little
words . . . Variable Displacement Compressor!

February 2019

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MACS Monthly Newsletter - 2019

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