Horn Question

[GAR64]

Finally got back to working on my 56 Fairlane. Have had it about three years and have posted some questions in the past. Actually, I posted a question about the horns before but never fixed it. Worked on it this morning. No horn when pushing the ring. So, I have power to the horn relay. If I jump power from center terminal on relay to the rear terminal, horn sounds. But, it sounds regardless of whether the horn ring is pressed or not! Is it simply a bad relay? I am concerned that replacing the relay with give me the constant horn thing. I know its a simple circuit but would appreciate an explanation from someone. Always enjoy this site...whether its for this car or the Model A I have also been spending time on. Thanks for any advice you may have.

 

[miker98038]

It's been a long time since I worked on one, and it's always possible the relay's been changed over the years. In general, if you're jumping between terminals, you're bypassing the relay. One term will be hot (the feed), one to the horn, and the third to the horn button. The horn button is a ground. It closes the relay, and the relay powers the horn.

You need to be a little careful, because if you jump the hot lead to ground you'll get a big spark, and/or a blown fuse. So time to dig the manual out and check the colors on the wires, and that they are on the proper terminals. Next, a VOM and see if the horn lead grounds when you push the ring. That might require helper to see the meter and push the ring at the same time.

 

[dmsfrr]

Here's a diagram of the (oem) horn circuit wiring.
As miker mentioned, there should be three terminals on the relay (in yellow box, 1st pic)
One for power from the battery (yellow wire)
another for power being sent to the horns (yellow/green wire)
and the last one connects to the slightly smaller wire up the steering column for the horn button. (blue/yellow)

When you jumpered power from the 'battery' terminal to the 'horn' terminal it sounds the horns.
(but you got that part already)

To check operation of the relay connect a jumper wire from the terminal on the relay for the 'steering column' wire to any bare metal on the body. One of the relay mounting screw/bolt heads should do.
This will complete the ground connection for the magnetic coil inside the relay that connects the power terminals for the horns.
If the horns don't sound the relay is likely bad. If the horns do sound you have a bad connection to ground thru the horn button and/or it's wire.

With any luck the relay terminals may be labeled... Horn, Battery, Switch.
If you have an Ohm meter and the relay is disconnected from the car you should be able to read resistance or continuity thru the internal relay coil, between the battery terminal and the switch/ground terminal.
.

 

[rick55]

At one time or another we have all had problems with the horn on our cars. Usuall the problem with them when they work whenever they feel like it gets down to a problem in the horn ring itself. There is a thick rubber pad behind the centre emblem which believe it or not is the culprit generally. If this rubber is faulty or failing you experience this problem. You can pack it out a bit to make it stiffer which will stop the contacts in the horn from shorting to earth whenever it wants to. The rubber pad can be replaced New ones of these are available from the restoration specialists If this doesn't cure it, the next culprit to look at is the horn switch wire itself. It runs up the centre of the column and if it is original it may have lost insulation causing it to short out intermittently. New ones of these are available from the restoration specialists. Should cost under $10.

 

[GAR64]

Thanks guys. I am going to look at it tomorrow. dmsfrr, are you saying that if I ground the steering column wire, the horn should sound? If this doesn't sound the horn, does that mean the relay is bad since the horn will sound when I jump from the center power terminal to the horn terminal? Or could it still be in the horn ring?

 

[dmsfrr]

If you touch a jumper wire from most any bare metal part on the car body, to the relay terminal where the steering column wire is attached, it should honk the horn. If it doesn't there's something wrong with the relay. If it honks the relay is fine.

As rick55 said, the problem is very often in the center of the steering wheel, where the horn wire grounding contact is.
The horn on mine wouldn't work when I first got the car. Someone had put the steering wheel horn ring spacer washers in backwards and it couldn't make contact.

 

[Daves55Sedan]

If you're in the rust belt, the horns themselves are more likely to be faulty, due to badly corroded body ground connection of the horn to the radiator support. To check operation of horn, bypass the relay altogether by connecting a insulated wire with alligator clips at both ends between the hot post of the battery and the wire terminal of the horn. If the horn does not sound, nothing you do from the relay on back to the horn button is gonna fix it. Remove the horn and grind rust off all surfaces that mate it to the radiator support. Often, the threaded studs and/or horn mounting bracket are the culprit and must be cleaned up. Use wire brushes, wire wheel on grinder motor and a tap and die set to clean off all rust. Coat all cleaned surfaces with a high-dielectric silicone compound prior to re-assembly and try the test again.
If the horns do sound by touching horn terminal direct to the battery, back track to the horn relay and touch a wire from the horn button terminal of the relay to body ground. The horn should sound.

 

[Daves55Sedan]

Just to clarify the way this thing is supposed to work; the horn wire that runs inside the steering tube is the ground connection. When you depress the horn button it completes the electric circuit causing the coil inside the relay to energize, closing the contacts and allowing current to travel to the horn terminals. If the horns themselves do not have good ground contact to the body, they will not operate.
Notice the heavy braided thermoplastic coated horn wire inside the steering shaft. Why is it like this? Because the horn wire is actually supposed to be stationary and does not rotate with the steering wheel, therefore there might be albeit minimal friction if the wire is touching the inside bore of the steering shaft. Most of these I have seen, there is a thin coating of 90 wt gear oil inside the bore of the steering shaft to reduce the amount of wear on the wire insulation. The height of the little spring that holds the horn wire terminal at its location is engineered to allow for steering shaft to rotate without twisting the horn wire along with it.
If the insulation of the horn wire becomes damaged inside the steering shaft, it will cause the horn to sound continuously.

 

[GAR64]

Dave, When I jump from hot terminal on relay, to horn terminal on relay, horn sounds nicely (not sure how this is getting grounded?). So, the problem is either the relay or the wire in the column. Dmsfrr suggested earlier that I connect a jumper from a good ground to the ground terminal on the relay, which is apparently where the steering column wire is attached. I assumed this would bypass the steering column wire. Horn did not sound. Should that have sounded the horn regardless of the wire in the steering column?? If so, I guess the relay is bad. Never good with this electrical stuff...but enjoying learning a little on some of these simple things.

 

[rick55]

If the relay doesn't pull in when you short the ground terminal to earth your relay is faulty and needs to be replaced. You are bypassing the steering column horn wire by doing this.

 

[dmsfrr]

..... I connect a jumper from a good ground to the ground terminal on the relay, which is ... where the steering column wire is attached. I assumed this would bypass the steering column wire. Horn did not sound. Should that have sounded the horn regardless of the wire in the steering column?? If so, I guess the relay is bad. Never good with this electrical stuff...but enjoying learning a little on some of these simple things.

If the relay doesn't pull in when you short the ground terminal to earth your relay is faulty and needs to be replaced. You are bypassing the steering column horn wire by doing this.

Yes, you are correct. The relay is not working as it should.

If you have an Ohm meter and the relay itself is disconnected /out of the car you should be able to read resistance or continuity thru the internal relay coil, between the 'Battery' terminal on the relay and the 'Switch/ground terminal'.
If the internal coil does not show resistance/continuity toss it and get a new one.

If the internal coil does show resistance/continuity, and you're curious, you can open up the relay by prying up the crimped tabs on the sides. Inside is a small spring loaded switch operated by the magnetism of the coil (when it is electrically grounded).
Sometimes the spring has slipped off the switch mechanism, or the switch lever is out of place.
Putting it back in place will often repair the relay.
This can save you the price of a new one, and it's why the tabs on the one on the right side in my photo above have been worked over.

Photo below... the two Ford/replacement relays I have are buttoned up, but this one is close enough to see what the insides look like.
.

 

[dmsfrr]

To test the horn wire and steering wheel horn switch.
If you don't have a Volt/Ohm meter this might be a good time to buy an inexpensive one.
... or make or buy a 12v test light.

Volt/Ohm meter.
Set it to ohms/resistance or continuity, connect one lead to the wire going up the steering column and the other lead to a good ground on the car.
Have your helper push on the horn ring/button. The meter should change from open circuit to 'zero' resistance (closed circuit) when the horn button is pushed. If it doesn't, the wire or switch inside the base of the steering wheel isn't making its connection.

Test light - 2 wires connected to a 12v light bulb.
Connect one wire of the test light to a wire from the '+' terminal of the battery.
Connect the other wire of the test light to the horn wire coming out of the steering column. Have your helper press the horn button, the bulb should light up.
If it doesn't, the wire or horn switch inside the steering wheel isn't making its connection.

.

 

[GAR64]

Thanks. Looks like I need a new relay. I do have a meter and a test light so I am going to check steering column wire too.

 

[Daves55Sedan]

Dmsfrr suggested earlier that I connect a jumper from a good ground to the ground terminal on the relay, which is apparently where the steering column wire is attached. I assumed this would bypass the steering column wire.

YES!

Horn did not sound. Should that have sounded the horn regardless of the wire in the steering column??

YES! HOWEVER, if the horns are no good (very possible), they are not going to work regardless what tests you run upstream of the relay as I suggested earlier. Best to begin by testing horns themselves first.

 

[Daves55Sedan]

Dave, When I jump from hot terminal on relay, to horn terminal on relay, horn sounds nicely (not sure how this is getting grounded

Okay got ya! So you did test horns individually and they do work. To answer your question, the horns themselves are grounded thru the bolted connection at the horn mounting brackets to the radiator support frame.

 

[Daves55Sedan]

If the relay doesn't pull in when you short the ground terminal to earth your relay is faulty and needs to be replaced. You are bypassing the steering column horn wire by doing this.

Rick is 100% correct and it is basically same thing I said in different terms.
The short answer is, the problem is most likely your horn relay is burned out.

 

[GAR64]

Replaced the relay. Horn works great. Nice sound. Thanks !