96 K1500 Brake/hazard Fuse Blows With Brake Application

[rickfinn123]

Noticed no flashers Y-day while towing a neighbors trailer. Disconected and replaced blown brake/hazard fuse. Flashers and turn signals worked until I touched the brake pedal - poof, fuse quickly re-blows.

Long story short, replaced the brake switch with no effect. Can someone help me? I could use some direction.

1. Is a wiring diagram available on line? 1996 k1500 350 auto

2. Am i right in thinking the short can't be back by the brake lights because the flashers/turn signals work? (same bulb).

[minibike132]

Noticed no flashers Y-day while towing a neighbors trailer. Disconected and replaced blown brake/hazard fuse. Flashers and turn signals worked until I touched the brake pedal - poof, fuse quickly re-blows.

Long story short, replaced the brake switch with no effect. Can someone help me? I could use some direction.

1. Is a wiring diagram available on line? 1996 k1500 350 auto

2. Am i right in thinking the short can't be back by the brake lights because the flashers/turn signals work? (same bulb).

 

 

Can't help you on a diagram but your thinking in #2 is incorrect. It's a dual filament bulb, same bulb different circuit.

[minibike132]

I take that back, it's a single filament bulb. The issue can't be at the rear but it can be at the CHMSL. If you can find a diagram I can help but I can't post one.

[rickfinn123]

Thanks Sparks!

I do have a Haynes diagram, but i don't understand it well. I disconnected the CHMSL, no change.

What does the stop lamp relay under the hood do?

Why is there a 10A "brake" fuse in addition to the 20A brake/hazard fuse?

The rear brake lights "flash" briefly as the fuse blows, so I think the broblem (short) is in one of the other legs of the white wire that exits the stop switch. Cruise control, CHMSL, or stop relay. The cruise is unaffected, so it can't be there? Could also be the turn/hazard switch, I guess,

I take that back, it's a single filament bulb. The issue can't be at the rear but it can be at the CHMSL. If you can find a diagram I can help but I can't post one.

[minibike132]

Thanks Sparks!

I do have a Haynes diagram, but i don't understand it well. I disconnected the CHMSL, no change.

What does the stop lamp relay under the hood do?

Why is there a 10A "brake" fuse in addition to the 20A brake/hazard fuse?

The rear brake lights "flash" briefly as the fuse blows, so I think the broblem (short) is in one of the other legs of the white wire that exits the stop switch. Cruise control, CHMSL, or stop relay. The cruise is unaffected, so it can't be there? Could also be the turn/hazard switch, I guess,

I take that back, it's a single filament bulb. The issue can't be at the rear but it can be at the CHMSL. If you can find a diagram I can help but I can't post one.

 

 

 

I'm not sure what the relay is supposed to be doing, the diagram I have can not be correct because it shows the circuit doing something redundant.

 

Before you go too crazy with a test light or meter take a look at the wiring harness near the parking brake bracket. That is a pretty common area for a dead short on this vehicle. I'm pretty sure some of the wires for this circuit are in that harness.

[rickfinn123]

My diagram is the same! Hot from brake switch splits and goes to the same point in the turn/hazard switch? One of the lines goes thru the stop relay. I'll look into the harness, thanks for the tip!

[rickfinn123]

Update! Found the 1>4 splice out of the brake switch. Isolated each and tested seperately. CHMSL is good! Brake relay under hood is good! Cruise wire doesn't short out!

Wire to turn/hazard switch is shorted! Not sure of my next step, might have to take a day off for other broken stuff!

[minibike132]

Update! Found the 1>4 splice out of the brake switch. Isolated each and tested seperately. CHMSL is good! Brake relay under hood is good! Cruise wire doesn't short out!

Wire to turn/hazard switch is shorted! Not sure of my next step, might have to take a day off for other broken stuff!

 

 

Sorry buddy, I got super busy this week. Did you fix this or do you still need some help?

[rickfinn123]

No sweat Sparks! I've been busy also.

The lights all work perfectly, but I am worried about driving with one of the four brake power "out" wires disconnected under the dash! All power is now coming thru the relay under the hood!

I intend to find a truck in the junk yard and trace the wire that is shorted on my truck. But I am open to ideas!

Thanks, Sparks!

Rick

Update! Found the 1>4 splice out of the brake switch. Isolated each and tested seperately. CHMSL is good! Brake relay under hood is good! Cruise wire doesn't short out!

Wire to turn/hazard switch is shorted! Not sure of my next step, might have to take a day off for other broken stuff!

 

 

Sorry buddy, I got super busy this week. Did you fix this or do you still need some help?