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73-87 Chevy _ GMC Trucks => 73-87 Chevy & GMC Trucks => Topic started by: chev2low63 on October 08, 2010, 08:23:07 pm

Title: 78 GMC sierra classic-Radio and Heater fan stay on after key is off
Post by: chev2low63 on October 08, 2010, 08:23:07 pm

First post... My 78 GMC Radio and heater fan stay on after the key is off. If I disconnect the battery and then reconnect, it doesnt come back on. Ignition switch??? any help would be very appreciated!! thanks

Title: Re: 78 GMC sierra classic-Radio and Heater fan stay on after key is off
Post by: Irish_Alley on October 08, 2010, 08:26:56 pm

First time I heard of this but like you said the only thing that I think it could be is the switch

Title: Re: 78 GMC sierra classic-Radio and Heater fan stay on after key is off
Post by: chev2low63 on October 08, 2010, 08:33:07 pm

thanks irish, im just gonna keep fishin around for a while. maybe its something stupid easy! ???

Title: Re: 78 GMC sierra classic-Radio and Heater fan stay on after key is off
Post by: Blazin on October 08, 2010, 08:59:50 pm

I had a 66 Chevy on a 70's chassis with a mix breed of 66 and 70's wiring. Had a kill switch, and a momentary push button switch to start it. The truck would shut off fine unless the wipers were on, then it would stay running until you shut them off!

Title: Re: 78 GMC sierra classic-Radio and Heater fan stay on after key is off
Post by: chev2low63 on October 08, 2010, 10:08:57 pm

one more thing to add:The light on the radio always comes on when the truck is on,  no matter if the radio is on or off. When I reconnect the battery and start the truck, if I dont turn the radio or the heater on it will go off when i turn the truck off. just brainstorming. thanks!

Title: Re: 78 GMC sierra classic-Radio and Heater fan stay on after key is off
Post by: zieg85 on October 09, 2010, 07:45:37 am

Sounds like a back feed from something being added.  What after-market stuff has been added? 

Title: Re: 78 GMC sierra classic-Radio and Heater fan stay on after key is off
Post by: chev2low63 on October 09, 2010, 08:46:43 am

There is a CD player is and there is an amp, those are the only aftermarket electronics. All I did was replace another deck and amp that was already in the truck.

Title: Re: 78 GMC sierra classic-Radio and Heater fan stay on after key is off
Post by: zieg85 on October 09, 2010, 10:09:41 am

Unhook the radio, does the heater fan stay on after the key is off?

Title: Re: 78 GMC sierra classic-Radio and Heater fan stay on after key is off
Post by: chev2low63 on October 23, 2010, 04:01:40 pm

the heater fan does stay on when the radio is unhooked. I also disconnected the heater fan and kept the radio powered and it still stays on. Another thing thats strange is when the truck is off the radio and heater are going if I hit the power window switch and hold it the radio will go off but when I let up on the switch it comes back on. Think im just gonna replace the ignition switch for starts. thanks everyone for helping!!

Title: Re: 78 GMC sierra classic-Radio and Heater fan stay on after key is off
Post by: chev2low63 on October 26, 2010, 07:00:43 pm

replaced ignition switch and its doing the same thing.

Title: Re: 78 GMC sierra classic-Radio and Heater fan stay on after key is off
Post by: Irish_Alley on October 26, 2010, 08:26:02 pm

How does your junction box look under the hood

Title: Re: 78 GMC sierra classic-Radio and Heater fan stay on after key is off
Post by: 75blazer on October 27, 2010, 12:03:45 am

happened to me recently. problem fixed itself but i learned it can be a couple things. 1. the ignition switch at the bottom on the steering column is loose or broken. 2. the rod inside the steering column can be out of adjustment (not likely).