Heater Problem

[mathteacherrob]

I have a 99 Old body Tahoe that the blower isn't working. I checked the motor and it runs when direct connected to a battery. I checked the voltage at the blower motor and I was getting 13.6 all the way up over 14 volts, even with the switch in the off position. Does that mean the switch is bad? With that many volts running to the motor shouldn't it be running all the time?

Help please

[j cAT]

Originally Posted by mathteacherrob

I have a 99 Old body Tahoe that the blower isn't working. I checked the motor and it runs when direct connected to a battery. I checked the voltage at the blower motor and I was getting 13.6 all the way up over 14 volts, even with the switch in the off position. Does that mean the switch is bad? With that many volts running to the motor shouldn't it be running all the time?

Help please

If this is automatic HVAC system I beleive that the logic circuit provides the ground path for the blower motor...

so if you place 12v across the motor and it runs, start by checking fuses..
could be hvac control module...fuses hvac 1, and FRT HVAC...

[777stickman]

If you don't have the system (auto HVAC) previously described then try these things.

You should have 2 wires at the blower motor. Black is ground (check for a good ground), purple is power.

2 fuses to pull while you're checking for power on the purple wire. 1) in the underhood fuse block pull the "blower" fuse #3 50a. Does the power go away? 2) In the I/P fuse block look for "HTR-AC" fuse #12 25a and check it for being good. Does the power go away when you pull that fuse?

Post back.