other Blower Motor Starts Strong, Then Shortly Peeters Out

[golf73]

when i turn on the heater fan, it works at full capacity, but then slows down to nothing within about 20 seconds. what is causing this to happen?

[Mike Self]

Coupla things to check:

 

1.  connect a voltmeter to the two terminals on the blower motor and see if you are still getting 12 volts after the motor slows; that'll tell you if the problem is in the wiring or the motor itself.  If you have a consistent 12 volts...

 

2.  closely examine the two brushes on the motor--see if they're worn or the plastic brush holders are deformed from overheating.  If the brush holders are all warped and/or the brushes are worn, they're not making good contact with the commutator ring and thus not providing full power to the motor.

 

3.  try drizzling a little oil on the exposed armature end (the end where the brushes are) and the upper bushing.  Don't use WD40, use a thin machine oil like 3 in 1.  The lower bushing (fan end) is almost impossible to reach with the motor in place, but you might try with an aerosol oil can fitted with a long, thin plastic straw.  Use a dental mirror to guide the straw. 

 

cheers & good luck

mike