Horn blares when my ac high low fan switch comes on

[alwaysbroken]

Alright so I’m having plenty of wiring issues with my k10 and just can’t seem to figure them out my horn comes on with my high and low fan switch and all my wires going to my courtesy light,dome light, and cargo light but it all ***** off completely if I take a light bulb out any one of those circuits…. I’ve been chasing this thing for a few days now and can’t can’t seem to figure out why white and orange are all hot

 

[Broken85]

My first thought is, WTF??

Second thought is, start with the basics. If someone crossed the HVAC over with the convenience center, your problem is under the dash not under the hood. I don’t know what year make or model you are working on, but maybe these will help.

 

[Grit dog]

Sounds like you bought a truck that was owned by an electrical genius. I’m sorry. My only suggestion is wiring diagrams and patience.

 

[Radiohead]

This

Sounds like you bought a truck that was owned by an electrical genius. I’m sorry. My only suggestion is wiring diagrams and patience.

This is the way.

You must trace out the wires in those circuits and see where the 'new and improved' comes along. Something is touching that shouldn't be and no amount of internet guesswork will help.

So, whatcha working on? '77 k10, right?

 

[Chevy 88]

Take 20 minutes and just re-wire the horn. Send the horn power wire to an always hot fuse, or even directly to the battery if you want it to be as quick and simple as possible.

 

[Grit dog]

@alwaysbroken, did you buy your truck from @Edelbrock?
Asking for a friend…

 

[alwaysbroken]

Sounds like you bought a truck that was owned by an electrical genius. I’m sorry. My only suggestion is wiring diagrams and patience.

When I first bought the truck all wires worked but my low beams and now it’s and one day they just all stopped working

 

[alwaysbroken]

This

This is the way.

You must trace out the wires in those circuits and see where the 'new and improved' comes along. Something is touching that shouldn't be and no amount of internet guesswork will help.

So, whatcha working on? '77 k10, right?

Yes sir it is a 77 4wd with the sm465 but I’ve ran a test light everywhere underneath the dash and to the fuse block my cab and under the dash every single orange and white is hot no matter what it is but none of my fuses have actually blown besides be hazard light but i replaced it and haven’t blow since and same thing

 

[Grit dog]

On the dome light circuit, orange is hot all the time. White is ground and effectively the switch for those lights. If white was hot it would be liveshorted across one of the lights I think.

 

[Broken85]

Maybe start with the door switches. Pull them out, they should have an orange wire attached. They are ground activated. If they are broke, rusted or permanently grounded in the panel, that would do it

 

[75gmck25]

Door switch wiring is white, and the switches ground the wiring when the door is open. Orange wires are the constant power feed to the interior lights, cigarette lighter, etc.

Horn wiring runs to a horn relay under the dash. IIRC, it is not plugged into the fuse panel, but is a separate relay.

Wiring for the blower high speed (not the lower speeds) runs through a blower relay mounted under the hood on the A/C plenum. The relay activates high speed through the dash switch, and/or also switches to high speed if the A/C control is on MAX/recirculate.
Power for blower high speed is through a separate fused line that runs across the top of the firewall, from the power junction near the brake booster over to the A/C plenum.

 

[chevdude]

Probably pisses people off on a hot day.

 

[edgephoto]

Start with the basics....Grounds. Don't look for the complicated or what if type issue.

Then grab the wiring diagrams and start diagnosing. I would start with the horn and work from there. See what is triggering the relay.