ACtion Magazine - March 2013 - (Page 31)
Replacement actuator
motor cautions
from HeaterTreater
M
ost technicians have heard it – a clicking noise
coming from under the dash. Of course, the noise
is often due to a broken gear in an actuator motor.
It can ultimately happen because a blend door
doesn’t turn smoothly, which imparts a twisting
force on the motor. This can skew the gears out of planarity,
causing eventual breakage. Most likely the motor will have to
be replaced. The blend door may or may not also be broken.
The technician can replace the motor with an OEM unit, but
research has shown that after some time, the failure may reoccur.
To further complicate matters, some aftermarket
replacement motors introduce another issue. These motors
are geared differently to lessen the stress on the gears. They
do it by using a lower gear ratio. Of course, this causes
the door to move slower (no real problem with that), but
with significantly more torque. OK, so the gears are less
susceptible to breaking, but now there is more force on the
door, and plastic doors that aren’t already broken will now
likely eventually break.
Figure 1, shows the internals of an OEM motor.
Figure 1.
Figure 2 shows the internals of an
aftermarket motor. Note the difference in the
number of teeth on the gears between the two
units.
Gear ratio affects torque. Think of a threespeed manual transmission in an old rear wheel
drive vehicle. In first gear, maximum torque
is transmitted to the driveshaft. This allows
the vehicle to easily move from a standing
start and pick up momentum. Shifting to
second gear decreases the amount of torque,
but allows the driveshaft to spin faster. Finally,
in third gear, there is maximum speed but
minimum applied torque. The same principles
apply to the actuator motors in the pictures.
Figure 2.
ACTION • March 2013
31
Table of Contents for the Digital Edition of ACtion Magazine - March 2013
ACtion Magazine - March 2013
Contents
Outlook
In Bin
Freeze Frame
Under the Southern Cross
Leonard’s Law
Virtual View
News & Updates
Managing the Heat
Delphi Restores 1954 Pontiac Star Chief With First ‘Front Mounted A/C System’
Replacement Actuator Motor Cautions From HeaterTreater
Association News
In Memorium
Quick Check
New Products & Services
Last Watch
ACtion Magazine - March 2013
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