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73-87 Chevy _ GMC Trucks => Interior & Equipment => Heating, Ventilation & Air Conditioning (HVAC) => Topic started by: 73c10Shorty on July 22, 2008, 12:34:24 pm

Title: Heater & A/C blower doesn't work on high speed
Post by: 73c10Shorty on July 22, 2008, 12:34:24 pm

So I'm still having problems with my A/C. I initially thought the switch was bad so I replaced it, but I still don't have high speed on the blower. Vile mentioned that it could be a relay. Does anybody have experience replacing this relay and possibly have a part # that I can reference?

Title: Re: Heater & A/C blower doesn't work on high speed
Post by: 73c10Shorty on July 23, 2008, 12:06:07 am

I found the relay and removed it. I'm going to replace it with a new one and see if that fixes the problem. After doing a little more research on this issue I'm confident that the relay will fix the issue. Yep... I should have listened to Vile's recommendation. In my defense... I had already ordered the switch. :)

Here's a link to where you can order a relay in case anyone else needs one.

http://www.classicparts.com/1973-77--Blower-Motor-Cut-Off-Relay/productinfo/68-341/

Title: Re: Heater & A/C blower doesn't work on high speed
Post by: VileZambonie on July 23, 2008, 04:49:42 am

You can get the relay at any autoparts store.

Title: Re: Heater & A/C blower doesn't work on high speed
Post by: 73c10Shorty on July 23, 2008, 11:56:54 am

You're right. I was able to get one from my local auto parts store. Unfortunately the new relay didn't solve the problem. I still don't have high speed on the blower. Any other ideas?

Title: Re: Heater & A/C blower doesn't work on high speed
Post by: VileZambonie on July 23, 2008, 12:03:09 pm

Let's start from scratch here. I was under the impression you TESTED it. #1 check the fuse. All speeds except high speed work? I assume when you checked/replaced your switch that you checked the connections and wires? How are the connections at the relay? i posted a schematic for this in another thread.

Title: Re: Heater & A/C blower doesn't work on high speed
Post by: 73c10Shorty on July 26, 2008, 06:00:14 pm

Yes, all speeds work except for high. All of the connections and wires look good at the switch and at the relay. Which fuse would I need to check? If it's not the fuse I think I'm going to have to take it to an electrical shop and let them figure it out. Thanks again for your help.

Title: Re: Heater & A/C blower doesn't work on high speed
Post by: choptop on July 27, 2008, 09:36:24 pm

What about the fan speed control resistor? (For lack of better words) non ac shown

Title: Re: Heater & A/C blower doesn't work on high speed
Post by: choptop on July 27, 2008, 09:41:07 pm

with a/c

Title: Re: Heater & A/C blower doesn't work on high speed
Post by: VileZambonie on July 27, 2008, 09:47:21 pm

The resistor is bypassed in high speed. The wire is basically jumpered to the motor.

Title: Re: Heater & A/C blower doesn't work on high speed
Post by: VileZambonie on July 27, 2008, 09:52:04 pm

My other post disappeared too. Make sure you check the B+ to the relay you replaced. On your truck there should be a fuse from the junction block

Title: Re: Heater & A/C blower doesn't work on high speed
Post by: Captkaos on July 27, 2008, 10:25:24 pm

I had to "fix" the post so everyone could reply.....