Tail/horn fuse

[Craig Burriss]

I’ve been chasing a gremlin that randomly blows the “Tail/Horn” fuse on my Duster. It’s a 71 wiring harness.
Is a 20amp fuse big enough for this circuit? I can’t find anything on sizes of fuses.
My horn contact ring in the steering wheel is screwed up so I have the horn relay unplugged. This is why I don’t think it would be the horn circuit blowing the fuse, but I cannot find anything wrong with the harness to the marker lights or running lights. I’ve removed the entire front and rear harnesses and carefully inspected every wire that has anything do to with lighting. It all looks pretty much brand new.
I’m tempted to put a jumper wire in the fuse box and see what melts first, just so I can find this thing that’s cost me about 1 fuse per 100 miles. But I’d rather not.
Any ideas?
Thanks

 

[eekvonzipper]

Maybe the Horn Relay is downwind of the fuse and the Horn Switch is Still the problem? Just Blabbing here... Got a Wiring Diagram?
I'd chase the circuit in my head b4 I'd add a Jumper and Multiply the problem.
Maybe Unplug the Horn Switch wire at the Steering Column Connector while it's screwed up

 

[Craig Burriss]

Maybe the Horn Relay is downwind of the fuse and the Horn Switch is Still the problem? Just Blabbing here... Got a Wiring Diagram?
I'd chase the circuit in my head b4 I'd add a Jumper and Multiply the problem.
Maybe Unplug the Horn Switch wire at the Steering Column Connector while it's screwed up

I'll try that. I've has so many wiring issues unrelated to the actual harness, I'll pretty much try anything at this point haha.

 

[eekvonzipper]

I just bought the "Full Color Laminated Wiring Diagram 11" X 17" on Fee-Bay...
Best $20 bucks I ever spent...

 

[67Dart273]

I think you are on the wrong track. Doesn't the tail fuse supply tail and lighter? I don't believe the horn supply line is even fused

The power to the horn relay is tapped off the big no1 splice under the dash

 

[eekvonzipper]

My Horn runs Straight off the Starter Relay (No Fuse) on my '65

 

[Craig Burriss]

I think you are on the wrong track. Doesn't the tail fuse supply tail and lighter? I don't believe the horn supply line is even fused

The power to the horn relay is tapped off the big no1 splice under the dash

I just assumed it was fused because on the fuse box, each fuse slot is labeled. This fuse says Tail and Horn

 

[67Dart273]

That is not what the diagram shows, either for 71 or 72, so ??

Easy to confirm.........get to the horn relay connector and probe the violet and see if it's "hot." Remove the fuse and see if it goes cold.

I would be checking over the cig lighter, and examining the rear harness for damage. Don't forget that the license lamp operates off the same tail wire, so tail/ marker/ license lamp.

Also pull the rear seat and examine the harness for damage in that area. Pull the rocker cover and look in there.

 

[Dana67Dart]

I’m tempted to put a jumper wire in the fuse box and see what melts first, just so I can find this thing that’s cost me about 1 fuse per 100 miles. But I’d rather not

Worst idea ever. Unless you are trying to burn your car and garage down.

First if you don't already have one is a wiring diagram.

Just tracing out my 67 dart wiring diagram I can find a dozen places where a grounded wire would pop a fuse. Down at the brake switch is a very possible point of a pinched / chaffed wire that will have intermittent contact yo ground.

In the imprtal words of 67dart273 (I think!) "and now a story from my past"

Worked in FacOps. Building ac system would shut off randomly. Found that it always happened the day after a rain.

I suspected the wires in a conduit that was very close to where someone had done some open flame welding.

No one would listen to me... But I persisted till one of the engineers agreeded to look at it.

Took him 40 minutes to remove 6 wires from 8 feet of conduit. Sure enough all the wires insulation was melted together. The melted insulation made a dam and when it rained, a leaking j box let in enough water to fill and make a short tripping the system.

Moral to the story look for the easy stuff and for the stuff that makes sense.

BTW fuses protect the wiring not the device. If you have a 40 amp fuse on a 20 amp circuit you just turned the wire in the cir to a 20 amp fuse.

Another thing to look at is the corrosion In the fuse holder. If the contact area that the fuse touches is corroded if will create a point of high resistance and create more heat, and a higher current right there at the fuse.