Horn Relay

[Jim Shepard]

OK, what is it? I've got the original 6 volt horn and when the truck was 12 volt it was nice and loud. When I reverted to 6 volt, the horn is barely a whimper. Someone said I needed a horn relay, but I'm sure it didn't have one originally and I don't see any reference to one in the wiring diagram. What does a relay do? Also, where do you hook it up?

[Norm's Coupe]

Jim,

I believe some horns only work as designed for either 6 or 12 volt. It may be you have a 12 volt only horn. A way to test is to run a jumper wire directly from your battery to the horn. If the horn doesn't blow loud that way, try a direct line from a 12 volt battery. If the horn is nice and loud on the 12 volt battery, you'll have to find a 6 volt horn to make it work right.

You do need a horn relay for the 6 volt horns though. If you have a service manual that goes into horn repair for trucks, it should discuss it there. Here is a pair of the trumpet 6 volt horns with the relay. The relay is where the pictures are centered. The small box with the wires leading to it. The horn relay cuts the horn on and off. If you had no relay, it would blow constantly with the wires hooked up. They are an extra pair I have hanging in the garage. Nice and loud. Thinking about making an alarm system for the garage and using them as the alarm horn.

[Jim Shepard]

Thanks for the response. My horn is 6 volt and, as I said, it worked nice and loud when the truck was 12 volt. It fact, it works fine if I wire it directly to a 6 volt battery. The problem comes when I connect it to the horn wire from the harness (brand new). I'm wondering if the 12 volt conversion wrecked it. So, is a relay I can find at Napa?

[Norm's Coupe]

If the horn blows good when you hook it up directly, it sounds like you just need the relay. Not sure if NAPA sells them. However, I've seen them on ebay from time to time. Plus I believe people like Roberts, etc. sell them. So they are out there. I know Tom Russom an old Mopar vendor who lives near me had some (or at least one or two) recently. Don't know if he still does or not. His email address should be listed with his profile in the member list here. He's registered under Thomas Russom.

[anthonyb]

I just replaced a horn relay after a small electrical adventure. I got it from O'Reilly Auto Parts. Not in stock but they had it in two days. They had both 6 and 12 volts versions.

[Reg Evans]

OK, what is it? I've got the original 6 volt horn and when the truck was 12 volt it was nice and loud. When I reverted to 6 volt, the horn is barely a whimper. Someone said I needed a horn relay, but I'm sure it didn't have one originally and I don't see any reference to one in the wiring diagram. What does a relay do? Also, where do you hook it up?

Jim, Is the horn more than a wimper if the truck is running at maybe 1000 rpm. My 35 Dodge does that. It won't honk unless the engine is running at a moderate rpm. I just purchased a relay for the 35 to see if that would cure the problem. You are right though. I've never seen a horn relay on a B series truck unless it had the dual horns.

[Merle Coggins]

Jim,

A relay allows a device to draw a higher current without it going through the switch. In other words, the switch used a low amperage to activate the relay which will connect a higher amperage for, in your case, the horn. It's possible that somewhere through your steering column you're not getting a good circuit. It may be enough to trip the relay though. If so, it'll fix your horn problem since you say it is nice and loud when connected directly to the battery.

Good luck,

Merle

[grey beard]

Gents,

The horn button is just a completion to ground - to complete the cricuit and make the horn blow. The horn relay is hot all the time - green wire from the Batt. terminal of the voltage regulator.

Having said all that, an asy test is to take a jumper wire and ground the wire that is not hot to a good ground surface. If the horn blows now, your horn button ground circuit is lousy or dirty, or the wire inside the column is not in good shape. My understanding is that the single Pilothouse horns do not use a relay, while the dual horns (mine is dual) use a relay. JMHO

Good lu k.

[Norm's Coupe]

Guys, I'm not into trucks so really not sure how their relays are set up. However, I think all vehicles had some type of horn relay on them, 6 or 12 volt, dual or single horns.

The reason I say that is because back in the early 60's I had a 58 Chevy. Battery kept running down on me. Horn did not work either. Finally found out why the battery kept running down. It was caused by a bad horn relay. Replaced the horn relay and battery stayed up and the horn worked again. The 58 Chevy only had one horn on it and it was also 12 volt.

[MBF]

I believe that there is an adjusting screw someplace on the horn that is used to adjust tone and volume. Since you're now running at half the voltage-twice the amperage is required to make the horn blow-you may have to back off on the adjustment if there is one visible. If your horn has a removable cup on the rear of the trumpet bell-the adjustment may be under the cup. MBF

[Merle Coggins]

Sorry Norm, I hate to disapoint you, but our trucks didn't use a horn relay. The horn had a direct power connection and were grounded to the steering column through the horn button.

However, I think Jims truck may benifit from a relay if his horn button can't carry the amperage to properly activate his horn.

Merle

[Norm's Coupe]

I believe that there is an adjusting screw someplace on the horn that is used to adjust tone and volume. Since you're now running at half the voltage-twice the amperage is required to make the horn blow-you may have to back off on the adjustment if there is one visible. If your horn has a removable cup on the rear of the trumpet bell-the adjustment may be under the cup. MBF

I don't think his problem is with the adjustment. If it were the horn would not work when he hooks it up directly to the battery, like it does. If it's not a relay problem, has to be something wrong with the wiring or ground.

Jim, when you rewired the truck did you use the proper gauge wiring harness. If it was a 12 volt harness the wire gauge is smaller and that could cause the problem on 6 volt. 6 volt systems take heavier wire.

[Jim Shepard]

I purchased a new harness from a reputable manufacturer with correct size wire. My horn work fine when hooked directly to a 6 volt battery. I'm thnking its the connection through the steering column. However, since the button is simply a connection to ground to complete the circut, any short would activate the horn. Right?

[Norm's Coupe]

Like Merle mentioned, you could have a poor ground someplace. Did you paint everything? If you did, you may not be making good contact for the ground. This is one of those where you gotta be there to figure out by trial and error until you locate the problem. Maybe check the circuit with a meter to see if you are getting all the current needed to blow the horn. Also make sure all connections are down to bare metal for a good ground. Really don't think it's the horn now. Start with the horn button on the steering wheel, make sure it makes good contact, then work your way to the horn.

[grey beard]

Just looked under the hoods of five Dodge Pilothouse parts trucks. All had single horns and none had relays on them. My own truck has dual horns and there is a relay sitting between the two. JMHO

[Jim Shepard]

I'll check the connections through the column.