Heater Blower and Blower Control

[rose359]

Heater blower did not function on the 1988 Scottsdale 3500 that I bought. This truck does not have A/C. I connected a 12 Volt power supply directly to the blower; it drew about 4 to 5 Amps and it sounded it like it was rotating slowly. So, I purchased and installed a new blower motor. While I was in the dash, I put in a resistor too. Made all of the connections, but blower doesn't run. Fuse is good and I verified that 12 Volts is getting to the switch (lower right contact on the cable connector shown in the photo). Is it the switch? I found one on eBay; switch, shipping, and tax will be $70. Has anyone had one of these switches fail? Thanks

 

[GMCTruck]

I would see if your getting 12V to the power wire that connects to the blower motor. If you are, then the switch is good and maybe the ground wire connected to the blower motor is bad.

 

[rose359]

I would see if your getting 12V to the power wire that connects to the blower motor. If you are, then the switch is good and maybe the ground wire connected to the blower motor is bad.

Today, I verified that the ground on the blower motor is good and that I have voltage at the connector. I got the blower to run on all three speeds, but when I tried it again the blower would not run at all. I verified the voltage at the connector again, but when I connected to the blower - nothing.

Next, I am going to get out the power supply and see if the blower will run. Electrical connections were so much easier before I installed the blower.

 

[rose359]

Today, I verified that the ground on the blower motor is good and that I have voltage at the connector. I got the blower to run on all three speeds, but when I tried it again the blower would not run at all. I verified the voltage at the connector again, but when I connected to the blower - nothing.

Next, I am going to get out the power supply and see if the blower will run. Electrical connections were so much easier before I installed the blower.

I verified that the blower motor runs off of the power supply connected to the leads on blower motor. I verified that the ground wire is good. Now, there is no voltage at the positive lead for the blower motor. So, I pulled the connector from the switch. The lead that formerly had 12 Volts is no voltage. I checked the fuse, and it is still good. Now I need to look up stream from the connector. The connector appears good, not like it has been overheated. What to do next?

Feb 21-22 will bring us 18"-24" followed by 40-50 MPH winds. So, no truck work for a bit.

 

[rose359]

I verified that the blower motor runs off of the power supply connected to the leads on blower motor. I verified that the ground wire is good. Now, there is no voltage at the positive lead for the blower motor. So, I pulled the connector from the switch. The lead that formerly had 12 Volts is no voltage. I checked the fuse, and it is still good. Now I need to look up stream from the connector. The connector appears good, not like it has been overheated. What to do next?

Feb 21-22 will bring us 18"-24" followed by 40-50 MPH winds. So, no truck work for a bit.

 

[rose359]

Due to snowfall overnight, they closed work. I got to work on my blower motor today. I knew the motor was bad; it would barely rotate when connected to a power supply. I replaced the blower and the resistor module. And, I replaced the 25 amp fuse. The fuse tested good but the plastic was a little melted. I didn't get the new fuse pressed in far enough to make contact. Now the fuse is fully seated and all three blower speeds work.