Posted to Technical Discussion Forum on 7/1/2015
GM HVAC Blower Motor Technology Changes
Reading the thread below related to the melted HVAC blower
motor connector, moved me to post about changes to GM blower
motor technology, that at least for GM pickup models was
introduced in the new body style 2014 models.
It seems that the DC brushed electric motor has been around
forever and for whatever reasons, GM engineers have moved to
adopt brush less AC motor technology. We can debate why, but
eliminating the annoying ticking of brushed motors at low
speed is reason enough.
With sensitive electronics susceptible to EMF and HFO-1234yf
refrigerant soon to be widely adopted as just a couple
reasons worthy of consideration, I'm sure that there are
other reasons we might think of other than keeping the
engineers busy! VBG.
So, when a student brought an HVAC blower motor to class
from a 2014-2015 something GM pickup truck that had been
replaced due to submersion in water, we "Curious Georges"
could not resist the temptation to take a look.
The traditional design "squirrel" cage or "hamster" wheel
that was pressed on during manufacture, was removed for
better viewing and the module cover on the back side removed
to reveal the controls board and 3 phase connections. What
remains is the AC motor. The stationary 3 phase windings can
just be seen in this view, Blower Motor 1 along with
the module heat sink. The control module and basic
connections for a simple bench operational test are shown
here. Control Side
Here Blower Control Logic is a "down and dirty"
re-creation of the basic circuit using the bare minimum to
operate the motor through a fused B+ jumper and B- to the
main terminals of the module and connecting our trusty
Kent-Moore signal generator Signal Generator to the
control circuit to replicate HVAC control signal inputs to
the blower motor logic module.
Increasing the duty cycle lowers the motor shaft RPM and
conversely, decreasing duty cycle increases shaft RPM. The
motor is almost silent and very powerful. With a strip of
photo tachometer tape affixed, I seem to recall around 4000
RPM being measured.
Of course, with the change in technology from DC or AC,
comes some revision in diagnostics. The AC motor does not
allow for traditional "bench testing" through connection of
power and ground to the older, most basic of DC blower
Martin from British Columbia
23 Replies Received
23 Replies Received