2002 GMC C3500 Heater high side

2002 GMC C3500
161,790 MILES • V8 • 4WD • AUTOMATIC
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CJSMITH6835
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Number 5 on the heater control doesn't work. One through four works fine as do all the other features. I used a test light on the electrical conection on the back side of the controls and when I turn the knob to the five position one of the wires loose power.
Thank you Corey Smith
Dec 1, 2009 at 3:52 PM
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DOCFIXIT
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Faulty high speed blower relay
Dec 1, 2009 at 4:09 PM
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JDL
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Welcome to the forum, the orange wire at the blower motor switch is voltage for high speed. That voltage goes to the coil side of blower relay, in order to energize relay, when relay is energized, only continuity for high speed circuit. When relay is not energized, continuity for lower speeds.
Dec 1, 2009 at 4:11 PM
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