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The Heater Fan in my 2000 Chevy Impala (3.8l, if it matters)use to work fine, but now it will only work and blow air when set on the hight "5" setting speed. What could be the problem? What can I do to fix it?
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The blower motor relay is energized when the Blower Motor Control is set to the High position. This removes the blower motor resistors from the circuit and battery voltage is then applied directly from the HVAC BLO fuse (RH IP Accessory Wiring Junction Block) to the blower motor though the relay switch contacts. The blower motor then runs at high speed.
HVAC Blower Controls Circuit Description
The blower motor is a variable speed motor. The motor operates at a higher rate when voltage is increased to the maximum level.
The blower motor resistors reduce the voltage supplied from the A/C FAN fuse (LH IP Accessory Wiring Junction Block) when the blower control is set at low and medium speeds (speeds 1-4). The blower motor relay is energized when the Blower Motor Control is set to the High position. This removes the blower motor resistors from the circuit and battery voltage is then applied directly from the HVAC BLO fuse (RH IP Accessory Wiring Junction Block) to the blower motor though the relay switch contacts. The blower motor then runs at high speed.
You may find a reset will solve this annoying problem. The problem you have is the GM heater control unit has lost it's
calibration, which can happen from time to time. The way to reset it is,
start your car and turn your heater off, and shut off the car, pull out
the keys. Then with vehicle off, disconnect the battery, (or batteries
if it has two). Let sit for 10 minutes, then re-connect battery. Get in and
start the engine, DON'T touch anything, let the heater control unit
re-calibrate for at least 40 seconds, (by the clock), then try turning
on the heater. Good luck!
mode door in ducting either stuck or failed --try turning the selector to another setting like floor /dash then another to see if it changes if no change actuator may have failed
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