1997 GMC C1500 Heater/AC blower will not work on HIGH.

Tiny
TRAFFIC272
  • MEMBER
  • 1997 GMC C1500
  • V8
  • 2WD
  • AUTOMATIC
  • 13,000 MILES
I have replaced the black BOSCH relay behind the glovebox, the blower RESISTOR and the blower MOTOR and still cannot get the blower to work on HIGH. I remember in older model years of GMC's and Chevys that their was a high speed blower relay that caused this issue.

If there is a HIGH SPEED relay, I can't find it. Any suggestions?

Thanks,
Jeff
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Thursday, June 12th, 2008 AT 9:58 PM

9 Replies

Tiny
RASMATAZ
  • MEMBER
See below


http://www.2carpros.com/forum/automotive_pictures/12900_relay_10.jpg

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Thursday, June 12th, 2008 AT 10:06 PM
Tiny
TRAFFIC272
  • MEMBER
I've already replaced the relay you refer to and the blower still does not work on high.

Thanks,

Jeff
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Thursday, June 12th, 2008 AT 10:24 PM
Tiny
MERLIN2021
  • EXPERT
Check the connector for signs of melting, could be the switch or the circuit to the blower relay.
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Friday, June 13th, 2008 AT 3:03 AM
Tiny
RASMATAZ
  • MEMBER
Turn control switch to Hi and look for power at the hi speed relay orange wire-No power either you have an open wire or the blower switch itself within the heater/ac control module-

Also check AC maxi fuse 50amp-it powers the hi speed relay
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Friday, June 13th, 2008 AT 6:20 AM
Tiny
TRAFFIC272
  • MEMBER
I've replaced the blower, relay, blower switch, and blower resistor and still have no high fan speed.
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Saturday, July 12th, 2008 AT 11:22 PM
Tiny
MERLIN2021
  • EXPERT
Must be wiring between the switch and relay, maybe the ground.
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Sunday, July 13th, 2008 AT 9:04 AM
Tiny
RASMATAZ
  • MEMBER
Here's the electrical wiring diagram-try tracking it from the HVAC module to the blower motor-


http://www.2carpros.com/forum/automotive_pictures/12900_switch1_1.jpg




http://www.2carpros.com/forum/automotive_pictures/12900_switch2_1.jpg




http://www.2carpros.com/forum/automotive_pictures/12900_switch_1.jpg

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Sunday, July 13th, 2008 AT 6:30 PM
Tiny
ROBERT GANN
  • MEMBER
Here is a possible solution for your 1995 GMC K1500 blower that wont work on high. First remove the glove box and set it aside. Now look into the area that the glove box resided. You will see a wire harness covered in factory foam and next to this on the right you will see a flat silver box that is your ECM. Now remove the foam covering gently because you will want to put this back on when your done. Now that you have removed the foam cover you will see a large junction connector and another connector with just a red and a black wire. Now what you want to do is turn on the ignition switch and the fan speed switch to high. Now gently grab ahold of the red and black wire connector and wiggle it if your fan came on you have found the problem. Now if this worked for you remove the positive battery wire from the battery because the red wire at this connector remains hot. Next disconnect the connector and look into the female side of the connector the red wire will show signs of it being loose, meaning that it looks like it has melted, This is due to a loose connection. Now if you opt to get a new GM connector or you can tighten the female connector so that the pin will fit snugly into it once again. Once this has been done you can put the connector back together you will see that the connectors still move when plugged back together. To fix this you will need a zip tie. Now put the zip tie between the red and black wires with the connector back together. Now pull the zip tie tight and cut the long end off with side cutters. Now reconnect your battery and turn your ignition switch back on and fan speed switch on high. The fan should be blowing on high, now wiggle the connector one more time the fan should stay on without interruption. Now put that foam covering back on just the way you found it. Push the wiring back in like you found it and then put you glove box back in. You shouldn't have anymore problems with the fan anymore if this was your problem
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Saturday, January 27th, 2018 AT 12:42 PM
Tiny
KEN
  • ADMIN
Great addition to this thread! Please feel free to help out whenever you are on the site :)

Cheers, Ken
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Tuesday, January 30th, 2018 AT 11:11 AM

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