My daughter is at college with her 75 auto, non tilt steering, 2 wheel drive.


Horn worked fine as of recently.


She called last night saying her horn stopped working. I had her check the jumper wire for the rag joint, jiggle it, and try again. No horn. I had her send a picture of the jumper. Looks fine.


I asked her to check the fuse, but said she did not see one for the horn. I looked on line and could not find a picture of a 75 fuse panel. I have the 77 shop manual but not a 75.


I mailed her a relay, in hopes that may fix the problem. I can TRY to have her take the horn pad off and check to se the wires are in place.


I am no expert, but have spent 3 hours reading up on this, but without the truck here it tough.


Any thoughts? Thanks.

 

99% percent chance it is the relay or corrosion at the connector. Let her replace that then worry if that does not fix it.

 

Thanks, we shall wait and see.

 

Also, the horn circuit is non-fused.

 

Test the relay by applying power directly to the energizing terminal.

Test the horn... they do sometimes die on their own.

 

The battery is good?

 

Thanks for the help. I believe the battery is good. I can have her go to a local parts store to test.


I did mail her two relays I had here, a wrench and a wire brush to do a swap.


I will reply back once I know something

 

I recently had a horn adventure on my 78 f100. In my case, there was no horn fuse. I think that the head light switch acts as a relay.

I would have her pull the power wire from the horn and use a circuit test light to see if there is even power going to the horn. If there is not, and you are using the original wheel, pull the horn pad and see if you can jump the two contacts and make the horn honk from that end.

If you can't, then your problem is somewhere in between, or even worse, there could be more than one issue.

In my case I was replacing my horn and steering wheel so I had a couple of things to chase.

 

I got a lesson this last weekend working on my wife's ride. The horn is always hot, it's the ground that is switched. The hot comes right off the battery, and the relay is usually mounted on the fender well or radiator support.

 

Here is a link to my original horn post... for reference. Maybe it will help.

https://www.ford-trucks.com/forums/1...lay-issue.html

 

good information and some good links. She should have the relay I sent along with the wrench, dielectric grease and a small wire brush. Lets see what happens. From the link that robothunderpants attached, could I also be looking at a bad headlight switch?


Thanks

 

1978/79 F100/350, Bronco & Econoline: No factory installed Speed Control, no horn relay.

1978/79's with Factory Speed Control: The horn relay plugs into the Speed Control amplifier.

 

I find it cool that your daughter is driving a 75 F100 to college, I've been grooming my 7 yr old daughter to love old trucks and cars. I just wish they had airbags and better seat belts.

 

EP145,
It is cool. In high school, she was certainly different. She certainly gets a lot of looks. We are very close to Boston and there are not many kids are driving trucks.


I have always had a passion for old vehicles and grew up around them. So she saw that.


My son, who is older, had ZERO interest.


I have the same concerns as you in terms of safety. Her truck is in need of a cab in a few years, so I am searching for a 76 and up replacement cab. During thanksgiving break I am going to install the safety features added to the hood in 78 and 79? The brackets which go on the inner fenders at the hood hinge, and the bracket at the rear of the hood that is supposed to help keep the hood from sliding into the cab.


Aside from that, I think she is a good driver and I hope that is enough.

 

Pic of 1978/79 Bronco showing these parts.