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73-87 Chevy _ GMC Trucks => Interior & Equipment => Heating, Ventilation & Air Conditioning (HVAC) => Topic started by: Neospartan on November 05, 2013, 10:03:11 am

Title: Heater problems
Post by: Neospartan on November 05, 2013, 10:03:11 am

Hello I'm new to the site this is my first post,
I have 73 C10 5.7L, the heater won't switch to HI only low and medium.
Also it won't shut off. Not a/c equipped. Thanks for the help.

Title: Re: Heater problems
Post by: 81_Chevy on November 05, 2013, 10:26:27 am

Most of the time with the heater not working on HI, or only on HI, its the selector switch that has gone bad. what have you tried so far to fix the problem?

Title: Re: Heater problems
Post by: Neospartan on November 05, 2013, 11:56:42 am

I haven't tried anything, I've been trying to do research and kinda coming up empty. I can't find a diagram of any kind on it.

Title: Re: Heater problems
Post by: bd on November 05, 2013, 03:53:00 pm

Hello and welcome to the Forum from Central California!

Quote from: Neospartan on November 05, 2013, 11:56:42 am

...I can't find a diagram of any kind on it.

See the 1973 Wiring Manual (http://www.73-87chevytrucks.com/techinfo/7387CKMans//Wiring/X_7305_1973_GMC_Truck_Wiring_Manual_CK_10_30_Pgs_Only.pdf) in the 1973-87(91) GM Pickup Manuals (http://forum.73-87chevytrucks.com/smforum/index.php?topic=25639.msg213706#msg213706) section of the Forum Technical Pages (http://forum.73-87chevytrucks.com/smforum/index.php?board=5.0).

The heater blower is designed to run on "low" speed whenever the ignition is switched on.  Never blowing on "high" speed is likely the blower switch, but could just as easily be poor connections.