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2002 GMC C3500 Heater high side

Tiny
CJSMITH6835
  • MEMBER
  • 2002 GMC C3500
  • V8
  • 4WD
  • AUTOMATIC
  • 161,790 MILES
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
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Tuesday, December 1st, 2009 AT 3:52 PM

2 Replies

Tiny
DOCFIXIT
  • MECHANIC
  • 18,828 POSTS
Faulty high speed blower relay
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Tuesday, December 1st, 2009 AT 4:09 PM
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
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.
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Tuesday, December 1st, 2009 AT 4:11 PM

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