The Stovebolt Site Forums The Shop Area The Electrical Bay Do I need a horn relay?

My 51 3100 came to me without a horn. I found a good one in a 53 chevy school bus. I took it apart,cleaned it up,repainted it and I'm ready to install it.The original wires are just laying under the hood with the connectors still on them from when the horn was removed. My truck was converted to 12 volts at some point. My question is do I need a horn relay? If the horn works without it what is it's purpose? Will I burn something out not using one?Also ,if I do need one ,how do I wire it?---Jack

Well probably not but what it does is help the horn switch just below the steering wheel last longer. All the relay is, is an electro magnet that has an internal switch. It is a coil of wire that moves a switch inside the relay case. That coil of wire probably draws milliamps where the horn draws several amps. One side of the coil is hooked to positive or the positive battery power, the other side to the switch in the steering column then the other side of the switch in the steering column to negative or negative battery terminal. When you press the horn button it closes the switch in the relay. So the relay has a positive lead connected to one side of the switch then the other side of the relay switch goes to the horn. The other side of the horn to negative. Remember that it is typical in autos to have the car frame be negative. So you may not have negative wires from the steering column. On my truck the positive lead comes down the column and the metal column is the negative.

Thank you. That is what I was looking for.---Jack

The 6 volt horn might not live too long at 12 volts. Was the bus converted? You might want a "ballast" resister to keep the horn alive. Just my 2 cents.

6 Volt horns will last forever at 12 volts.

I have "burned out" horns by steady-honking for too long.

I'd bet a 6v horn would "burn out" more quickly when using 12v (and, not last forever)?

I'll revise my statement then: Under regular use, it will last nearly forever on 12V.

It's common to hook them up to 12V and they work very well that way, nothing to be afraid of. Any horn isn't mean to be steady-honked for a long period, and you'll likely burn out something with the amount of current that would be running through it for a prolonged period.

I burned my horn out in the 5-mile 11pm parade for a soccer team when they got back to town after winning the NYS championship.

Not normal use of a horn.

Just like the 6v starter with 12v battery, be easy on the duration of continuous use.

Also, the wiring in a 6V system is larger than required for 12V. So, at 12V, the horn system is less stressed and should be fine without a relay.

You should still use a horn relay to reduce the current going through the switch.

Sounds like TC deserves a new nickname. LOL.