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Ignition switch ouestions

Old 01-29-2018, 03:20 PM
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You say that the relay is good, does it operate when the key is turned on and off? If it does is there +12 volts at the blower motor to ground at a body point not the other wire. If yes then the fuses and relay are working properly and so is the ign switch and the problem is down stream of the blower motor on the way to ground. If no power and you have tried a new replacement relay and can hear/feel it operate when the key is turned on and off, then you have a damaged/burnt wire/connector from the relay to the fan motor. Check the contacts under the pdc for the replay. Ive seen cases where the terminals under the PDC have burnt and no longer make contact. If you can't repair the contacts under the pdc and replacing the whole pdc is not realistic you can extend the wires and bring them up into the open and have the fan relay operate outside of the pdc.
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Kerley (01-31-2018)
Old 03-14-2018, 07:58 AM
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Originally Posted by Busboy View Post
There are 2 fuses for the blower one inside and one under the hood there is also a relay that is powered on with the ignition switch through one of the fuses.
I'm still trying to figure this out, so please bear with me. All power starts with the batteries, then to the inside fuse, then to the Ignition switch, then to the PDC fuse and relay to the HVAC control switch on the dash to Blower Motor. Am I on the right track?
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Old 05-21-2018, 05:31 PM
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Originally Posted by Busboy View Post
The fuse in the PDC is what powers the blower motor, the fuse in the junction block fuse panel inside the truck is for the "control" of the relay and the relay is in the PDC under the hood. The relay is operated by the ignition switch so when the key is on the relay provides power to the blower motor and the ground is what is switched. With the key on there should be +12 volts at the blower motor even if it's selected off. What causes the resistor block to burn out is insufficient air flow to cool it. That can be from a partially plugged evaporator core or a bad blower motor.
All fuses are good, the relay in the PDC has voltage, I also installed a new relay in the PDC to be sure it works. With the ignition off or on and the HVAC Control *****, set on AC, there is no voltage to the Blower Fan, I used a 12v jumper from the battery to the blower motor with AC switched on and the blower worked as it should, and I had cold AC, so the problem is power to the Blower Motor. I am stumped, and thinking the cure would be to replace the Ignition Starter Switch. I found a drawing with reference to a relay inside the HVAC Housing, above the Blower motor, is this relay something you are knowledgeable about? I would appreciate guidance. Thank you, Kerley
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