Heater does not blow any air

Tiny
DAREN SPORLEDER
  • MEMBER
  • 1995 CHEVROLET SILVERADO
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 150,000 MILES
Heater does not blow. I have replaced blower motor, coil resistor, switch and fuse. Still nothing. What else is left to check?
Thursday, December 28th, 2017 AT 12:24 PM

1 Reply

Tiny
CARADIODOC
  • MECHANIC
  • 33,916 POSTS
There are two versions of heater fan circuit. The heater-only has two fuses and a common-sense switching circuit. If either fuse was blown, you would still have either the highest speed or all except the highest speed.

If you have air conditioning, the engineers needed to complicate the circuit unnecessarily with an unreliable computer. There are three fuses for this circuit. It is not likely all three are blown. Go to the resistor assembly and check for twelve volts on the red wire. If that is missing, the 50-amp "AC fuse" is blown. This fuse is in the under-hood fuse box.

Go to the heater and AC control module and check for twelve volts on the brown wire. If that is missing, check the 25-amp "heater/AC fuse". That one is inside.

Check for twelve volts on the two wires for the motor, but these are only valid if the connector is plugged in. Back-probe through the connector next to the wires. If you find twelve volts on both wires, the ground circuit is open.
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Thursday, December 28th, 2017 AT 2:05 PM

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