high heat setting doesn't work

[mike 1985]

My 85 vette high heating setting doesn't work. According to the local vette shop this is common, however they won't give any additional info out.

How can i trouble shoot this th determine if it's the switch in the dash or the blower motor? All the other settings work, just not the high


thanks

 

[Eagle85C4]

The problem is neither....follow the wires back from the blower and you will find a connector between the exhaust manifold and the firewall on the backside of the a/c coil on the passenger side. Usually the black ground wire gets hot and melts the connector. Once the ground wire is broke you loose the high setting but the low and mi9d setting still works as the circuit for them is a bit different then the high circuit. My Haynes manual does show a great schematic for the wiring of both and I would be glad to scan it for you if you need it.
I had the same problem and had many folks look at it , they tried the blower motor, the relay, the resistors for the low and mid circuits to no avail, I finally found the problem myself and have come to the rescue of several others with the same problem.
Now to fix it I removed the wires from the connector and spliced it together as I felt that the connector was just a problem waiting to ruin my day and removed it and spliced the wires together. No more problem...

 

[mike 1985]

thanks,

I have the haynes manual also and have read it page for page and must of missed that. I'll track it down tonight and elim the connector as you did.

thanks again for your help, it's much appreciated

 

[mike 1985]

ok, itracked the black wire back to a plug bt the a/c coil. Mine not by the firewall, it's closer to the larger ac lines. Anyway there's like a cluster (4) of ground wires there all soldered together, one goes to the wiper motor,which works when a hot jumper wire is placed into the hot plug, one goes to the heater fan, one to an a/c sensor and the other through a huge wire look back by the fire wall. I checked the power at the relay and found that all 3 lower settings go to the blue wire and that the orange wire is for the high setting ( as the schematic in the book describes) and when the switch is turned to high the orange wire gets power, but does not transfer through the relay to the black/red wire. So i replaced the relay with an autozone relay and as soon as i turn the switch to high it blows a 25 amp fuse labled a/c in the upper right corner of the fuse box ???


I'm not an electrical guy and this is really troubling me. Any suggestions or can you give me a better idea of where this ground plug might be?

thanks
Mike


HUM where is that little animatied guy beating his head against the wall

 

[berky2500]

Thanks for the info Eagle, mine has the same problem, now I have a place to look.