It's starting to get cold in Michigan and I need some heat the enjoy the drive. The heater motor fan at full blast does not seem to run very fast. Does the resistor affect full speed, or should I replace the fan motor.

In some of the vettes the high heater blower has it's own separate resistor.  Not sure about the 75.

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I dont want to stomp on your thread, but mine has only high speed on the fan. I replaced the fan switch without positive results. Maybe I will get my answer too.

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The high speed runs off of a dedicated relay...no resistors for that. The relay is normally attached to the A/C plenum under the hood, close to the resistor block for the fan motor.
If the fan is running with the switch on High, the relay is working. If it seems the fan is slow, the fan itself is most likely the problem.
If you only have High speed, the problem is most likely the resistor block, or possibly a fuse.


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Joel Adams
C3VR Lifetime Member #56    
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

What the apple said, ya, ah huh.

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One thing about my vehicle, it does not have AC. I do not see a relay.

The contacts on the resistor are bad about getting corroded.  Pull them off and clean both sides of the solderless connectors and plug back in, that may be a quick fix to your problem.  I also had to work on my relay which was mounted on the firewall.  The points had "fused" together and would stick, not allowing the relay to return to the "off" position.  A little 200 grit abrasive paper slid between the points a few times and the relay was working again. Ill eventyally have to replace it but its been working after that "bubba" fix for 2 years.  If anyone needs pics of where the relay and resistors are located give a shout, I have pics of where they are on an 82 and think they are pretty much in the same place on most sharks. Crossfire19822009-10-31 06:52:51

Ok, please send pics.

OK, here is a pic of the blower resistor and relay.  You may have to move the wiring harness a bit to get to the base of the resistor but its not difficult to get to really  The resistor itself is inside of the air plenum.  The resistor is quite long and you can see only the base of it until you remove the screws and pull it out of the plenum in order to make sure the wire coils which make up the resistor are intact and not broken.

Thanks for the photo, but my vehicle does not have AC

I think non AC vehicles do not have a relay and is the resistor in the same place?

Non-A/C will NOT have the high speed relay, but it will have the resistor. The resistor on your car should be on the inside of the car, mounted to the air box/plenum under the dash. Problem is, it MAY be on the side towards the firewall... I'm not remembering...
If you take a look under the dash, on the passenger side, the heater plenum is there. The resistor will either be staring you right in the face, or it will be on the opposite side, next to the firewall, which makes it really hard to get to. It will look similar to the resistor that Crossfire1982 posted, just in a different place.


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Joel Adams
C3VR Lifetime Member #56    
My Link


(click for Texas-sized view!)             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Ok, put in a new Blower motor and a fan switch. I have high speed and the low below it, but no slow speed. Changing out the resistor will be the next step, hopefully it will not be too hard to get to. The car has no AC, so the resistor is on the heater core and is assessed from the inside. That will be Saturday's job.

Yup, thats the way the resistor looks on my car.  Cept I do not have all the shinny stuff on my hoses.  I'm a "stock" kinda guy.

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