A/C / Heater Blower - The 1947 - Present Chevrolet & GMC Truck Message Board Network

twxsby · 05-11-2004, 11:54 AM

The blower for the A/C / Heater stopped working, and I can't figure out why. I jumped the blower to the battery, and it comes on. I have 12 V on the fat red wire into the blower relay, but nowhere else. I bought a new relay, but that didn't fix it. I checked all fuses (can't tell which one is for the blower, so I am looking for a diagram of the fuse block as well). Any Ideas? This happened before, but it fixed itself after a few days. Thanks!

Grim Reaper · 05-12-2004, 09:36 AM

The Fat red wire is high only. If you have no speeds it's a control issue. On the side of the box is another set of wires into a plug. that's you low speed blower resistors. Just so you know.

Even in the off posisiton the fan should run in a very low speed. If it's not then it control and possibly a issue with the ignition switch. Check the plug on the colum and make sure it didn't get kicked. It's on the top of the colum about midway between the dash and floor.

Done anything under the dash recently? Anything else not working?

Check all the fuses. I dont have my truck here today but I think one is marked HVAC or Blower. I'd have to look again but I seem to recall the A/C trucks had a fusable link under the hood. It's either tied into that block on the fire wall hanging down betwwn the brake booster and engine or it's down at the starter.

twxsby · 05-12-2004, 09:24 PM

I found the problem, but I don't know how to fix it (the right way). I am only getting 3 volts to the switch. I jumped a wire from the fuse panel to the switch and Bingo, it works. How do I find the problem? Should I abandon the original wire, and hook up a new one?
Thanks

Grim Reaper · 05-13-2004, 09:35 AM

Hmmm 3v is very bad.Is the fan on low when you turn the key to run? It has to be on when the key is on. NO way to turn it off. If it's not running on low even with the dash controls to off something is not right and possbly could cause other electrical problems.

If it is not running at all I would start checking the Ignition switch on the top of the colum. All the power for the blow runs through it and no blower at all indicates either blowfuse/fusablelink or bad switch.

Krosati · 06-05-2004, 01:23 AM

With the ignition on an the AC off, should the blower be running at a slow speed?
Or does this indicate a potential problem?

05-11-2004, 11:54 AM	#1
twxsby Registered User Join Date: Apr 2003 Location: Cypress, TX Posts: 81	A/C / Heater Blower The blower for the A/C / Heater stopped working, and I can't figure out why. I jumped the blower to the battery, and it comes on. I have 12 V on the fat red wire into the blower relay, but nowhere else. I bought a new relay, but that didn't fix it. I checked all fuses (can't tell which one is for the blower, so I am looking for a diagram of the fuse block as well). Any Ideas? This happened before, but it fixed itself after a few days. Thanks! __________________ 84 K-20 Burb 94 Ranger 4X4

05-12-2004, 09:36 AM	#2
Grim Reaper Registered User Join Date: Jul 2001 Location: Atlanta GA Posts: 1,704	The Fat red wire is high only. If you have no speeds it's a control issue. On the side of the box is another set of wires into a plug. that's you low speed blower resistors. Just so you know. Even in the off posisiton the fan should run in a very low speed. If it's not then it control and possibly a issue with the ignition switch. Check the plug on the colum and make sure it didn't get kicked. It's on the top of the colum about midway between the dash and floor. Done anything under the dash recently? Anything else not working? Check all the fuses. I dont have my truck here today but I think one is marked HVAC or Blower. I'd have to look again but I seem to recall the A/C trucks had a fusable link under the hood. It's either tied into that block on the fire wall hanging down betwwn the brake booster and engine or it's down at the starter. __________________ Grim-Reaper 70 Pontiac LeMans Sport Convertible, worlds longest resto in progress Looking for 71-72 2wd Blazer or Jimmy Project

05-12-2004, 09:24 PM	#3
twxsby Registered User Join Date: Apr 2003 Location: Cypress, TX Posts: 81	I found the problem, but I don't know how to fix it (the right way). I am only getting 3 volts to the switch. I jumped a wire from the fuse panel to the switch and Bingo, it works. How do I find the problem? Should I abandon the original wire, and hook up a new one? Thanks __________________ 84 K-20 Burb 94 Ranger 4X4

05-13-2004, 09:35 AM	#4
Grim Reaper Registered User Join Date: Jul 2001 Location: Atlanta GA Posts: 1,704	Hmmm 3v is very bad.Is the fan on low when you turn the key to run? It has to be on when the key is on. NO way to turn it off. If it's not running on low even with the dash controls to off something is not right and possbly could cause other electrical problems. If it is not running at all I would start checking the Ignition switch on the top of the colum. All the power for the blow runs through it and no blower at all indicates either blowfuse/fusablelink or bad switch. __________________ Grim-Reaper 70 Pontiac LeMans Sport Convertible, worlds longest resto in progress Looking for 71-72 2wd Blazer or Jimmy Project

06-05-2004, 01:23 AM	#5
Krosati Registered User Join Date: Jul 2003 Location: Texas Posts: 49	With the ignition on an the AC off, should the blower be running at a slow speed? Or does this indicate a potential problem?



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