Hello,

Did some searching but I couldn’t find any threads on engine bay component identification. I have a 1968 Cutlass S Holiday Coupe that originally had a 350 2bbl carb, power brakes, power steering, and factory A/C. I am having trouble with my horn. I have identified the horn relay and have a new one coming today. It is connected to another small metal box mounted on the firewall just above the brake booster. Can anyone tell me what that is and if it might also need to be replaced?

 

Here is a picture of the component I am asking about

 

Have you checked if the horns work? Jumper their power tab directly to battery positive.

 

I will check the horns themselves

 

YES! I just went through this problem with my 72 442 and I checked things other members mentioned BUT, I started with the horn button on the steering wheel and moved forward. Not being electrically competent and slightly colorblind, it took me a while to get to the horns!! Guess what, both horns were non-functional I checked with jumper wires and then removed them and checked them at the battery. D-E-A-D! I bought a set of repro Delco Remy horns and installed them and now it is loud and sounds like a 1970's GM car! So yes.....check the horns early! BTW, my 72 only has 47, 900 miles on it but the horns are 53 years old, and it has sat a lot over the years!!

Good luck with your diagnosis,
OLE442

 

The relay on the firewall is the high speed blower relay for A/C cars. It has nothing to do with the horns. The horn relay also serves as a 12V power source for other accessories via the threaded post. That's why there's a wire from the horn relay to the high speed blower relay.

Back to your original problem, exactly what problems are you having with the horn. Once again, throwing parts at a problem without first performing simple diagnostics is a great way to waste time and money in addition to potentially introducing new and creative failure modes. There are only four steps needed to diagnose the horn (and frankly it seems that I have to type this about once a week).

1) Verify that there is battery voltage at the threaded stud on the horn relay. If not, find the problem in the red wire from the battery.
2) Disconnect the green wires at the horns and run a jumper from each horn to +12V on the battery. Does each one work? If not, replace the horns. If it works, reconnect the green wires.
3) Disconnect the green wire at the horn relay. Jumper this wire to +12V. Do the horns work? If not, find the problem with the green wire between there and the horns. If it works, reconnect the green wire.
4) Disconnect the black wire at the horn relay. Jumper the relay terminal to ground. Do the horns work? If not, replace the horn relay. If the horns work, find the problem in the black wire from there to the horn button.

 

Thanks Joe! Great step by step trouble shooting tips. I must admit I am usually intimidated by electrical issues. Your advice will help.

 

Checked the horns and they both work. Power is getting to the horn relay and the relay is functioning properly. Now it must be the black wire that runs from the horn relay to the “alternator and front extension connector” on the firewall below the brake booster. Can this connector be disconnected at the firewall so I can test from there to the brake booster to make sure the black wire is not broken? It is wrapped with all the other wires coming from that connector to the horn relay and some other ones. It is tough to reach under that booster, but looks like it has a hex bolt connecting it to the firewall.

 

For someone who claims no electrical chops, you are doing well!

But it may be less likely that a wire broke and more likely that a contact failed.

It may be better to start at the termination of that black wire (at the top of the steering column).

Disconnect the battery, remove the steering wheel and the horn contact. Reconnect battery and ground the black wire. If it activates the horns, the problem is in the horn contact apparatus.

 

The black wire runs to the horn button on the steering wheel. While it is possible that the wire or firewall connector is bad, it's far more likely that the problem is in the steering wheel. I would start by disconnecting the steering column connector under the dash and jumper that black wire to ground. If the horns work, the problem is in the column or steering wheel.