Question about GMC Cars & Trucks
There is no relay in this vehicle. Power flows from the fuse to the speed switch. For the slower speeds it then flows to the blower motor resistor and then to the blower motor and ground. For high speed power flows from the switch directly to the blower motor and then ground. Check for battery voltage at the switch on the Brown wire. That's incoming power. Also check for good ground on the black wire at the blower motor.
Posted on Oct 09, 2019
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Posted on Jan 02, 2017
I just found my problem that often brings in a Check Engine light, and reads out a PO 442 code. When my A/C is on my heater would start working because a vacuum operated control door would slam shut when accelerating. Also my cruise control would stop when going up a large incline.
the first thing to check, and easy is the cruise control for a bladder leak. Look on the top side passenger side of the firewall, and you will find a three way vacuum hose connection. One will be a very small black plastic line that runs to the cruise vacuum actuator. Pull this hose loose at the fire wall connection. Blow in this hose, and if it will not hold pressure, and in my case I could hear air passing through it is defective needing replacement. Block off the firewall connection for A temporary fix.
Posted on May 08, 2009
SOURCE: No AC, heat, or vent
its sounds like the Blower speed controller, its located under the hood on the heater case. reach down a wiggle the connector, its under the heater hoses and attached to the case. If it starts the blower fan working get it replaced as it has a bad board.
Posted on Aug 09, 2009
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