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Heater blows sometime

Tiny
REARDRIVE
  • MEMBER
  • 1992 CADILLAC DEVILLE
  • 4.9L
  • V8
  • FWD
  • AUTOMATIC
  • 231,205 MILES
Sometime I start the car turn the heater on it will blow fine but when I turn the switch off, when I restart the car the heater blower will not blow. A day or two it may start back blowing. I put on a new thermostat and a new T tube
Saturday, January 7th, 2017 AT 4:07 PM

1 Reply

Tiny
CARADIODOC
  • MECHANIC
  • 33,864 POSTS
That is the classic symptom of worn brushes inside the fan motor. A clue is it will often start working when you bang on the heater box. Once it starts running, it will not fail to continue running until you turn it off.

It is possible for an overheated connector terminal or fan speed switch to cause intermittent operation too. But those do not take long before they become a permanent failure.
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Sunday, January 8th, 2017 AT 3:02 PM

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