MACS Monthly Newsletter - 2017 - FEB1

Total Vehicle Climate and Thermal ManagementTM

February 2017

By Paul Weissler - MACS Senior Correspondent

ONCE MORE: IS REREPROGAMMING FOR YOU?
descriptions of the effects of the calibrations are rarely so
detailed that you can be absolutely positively sure.
Here's a case from a 12-year-old Saturn Relay, a minivan built on the same platform as the Chevy Uplander
and Pontiac Montana, but with the 3.5-liter V6. This engine, FYI, is not the Honda engine used in the Vue; it's
a General Motors engine with a cast-iron block that was
shared with a longer-stroke 3.9-liter V6 edition. Problem is no front heat, plenty of heat from the rear system.
There were codes, but interestingly only for the rear system controls, which the technician cleared (and on which
he performed a system recalibration, to no effect). However, the rear system is controllable from both the front
control panel and the rear DVD panel, which houses the
rear HVAC knobs.
The rear system, housed behind the left rear quarter
panel trim, includes an evaporator, heater core, blower,
mode and temperature control actuators. The mode actuator is in the ductwork assembly built. There were
two codes, P0428 (rear heat temperature control) and B
3532 (rear mode control of airflow). So why are there
codes for the functioning rear system and none for the
malfunctioning (no heat) front system? There's no simple answer, because these could be history codes, logged
during odd-cycle events, but that have not yet erased (it
takes 100 cycles in this system to erase a code that has not
reappeared). Or it could be a simple software anomaly in
a module that affects both front and rear systems. That
module is the front HVAC module.
The technician disconnected a front actuator and

Paul Weissler

We still hear HVAC (and other) technicians saying
there just isn't enough aftermarket business in reflashing
modules (FIG. 1), that most of what they have to do is
just reinitializing actuators. When we look at the service
bulletins, we'd say they're just missing a lot of opportunities. And just because a customer never has had a longlisted reflash doesn't mean it doesn't apply now. It may
involve a previous owner (or even the present owner)
who just never encountered the situation. Perhaps the
issue covered by the new software is the car is in the shop
now, it isn't an easy decision, because unless there's an
accompanying service bulletin, with many makes, the

Figure 1: Reprogramming may not be a certain, total fix, but if the software
lists the car, the procedure is becoming straightforward, using an SAE J2534
Pass-Thru reprogrammer and a cable to the under-dash OBD2 connector and
software from a personal computer tied to an internet connection, plus a specific
battery charger that maintains a "clean" state of charge for the car battery.

ALSO INSIDE THIS ISSUE:
Repeat heater core failures............................................................................................................................................... 2
As we say, look at the wiring diagram ............................................................................................................................. 3
Refrigerant identification, now another choice .............................................................................................................. 4
When there's more than one............................................................................................................................................. 5
No A/C-Ambient/outside temperature sensor reading................................................................................................. 6
Dead battery or very-low voltage ..................................................................................................................................... 8
MACS Service Reports is the official technical publication of the
Mobile Air Conditioning Society Worldwide, Inc., P.O. Box 88,
Lansdale, PA 19446. The material published in MACS Service
Reports expresses the views of the contributors and not necessarily that of MACS. Every attempt has been made to ensure

February 2017

the accuracy of the content of MACS Service Reports. MACS,
however, will not be responsible for the accuracy of the information published nor will MACS Worldwide be liable in any way for
injury, labor, parts or other expenses resulting from the use of
information appearing in MACS Service Reports.

MACS Service Reports

Table of Contents for the Digital Edition of MACS Monthly Newsletter - 2017