K 2500 Truck 4WD V8-379 6.2L DSL VIN C FI (1989)
Blower Motor Does Not Run In Medium
High Blower Operation With Ignition Switch Off
Some vehicles may experience high blower operation with ignition key "OFF." This may be caused by a back feed voltage applied to circuit 50, which
powers the blower "OFF." This back feed voltage could be produced by a defective diode in alternator rectifier bridge. To diagnose this problem,
proceed as follows:
1.
With ignition key "OFF," disconnect circuit 250 (brown field wire) from generator.
2.
If blower motor stops, remove alternator and replace rectifier bridge if equipped with serviceable alternator or replace alternator in equipped with
a non-serviceable alternator.
