Dead Horn Troubleshooting....

S

Scotts216

Junior Member
Hello All, and Happy Memorial Day.....

I am in the process of prepping my late father's 31" coupe to find it new home.

It's been in the family for decades and was an older ground up restoration.

The horn is DEAD, and I could use some help/tips on troubleshooting. I am a car guy but not specifically educated on Model A's even though they are pretty simple.

A few thoughts:

When I push the horn button, the ammeter gauge ticks to the left whether or not the key is on? Shorted button?

Dad soldered the wires from the horn to the harness, so I may have to cut to pull horn and bench test. I assume that I add 6V to the 2 terminals underneath and see if it works?

What is the best way to use external 6V to try horn while in car?

I had the rear cover off of the horn and went to move the armature shaft and accidently touched the mount frame and got a spark with key off? I would think I should not have any voltage there with key off?

I have not been able to figure out how to get to the horn button switch on the steering wheel? I think it has a C clip at the bottom of the steering column that when removed allows the rod to be pulled out. Thus far I have not seen or felt that??

All I know.....

Any thoughts or advice on troubleshooting appreciated.....

Thanks, Scott in Colorado
 
Your button is fine. There should always be power to the horn. The button grounds the other side of the horn to make the motor run. Back off on the adjusting screw until the motor runs free. Let it come up to speed, if it will, and run it for about 15 seconds. If it seems powerful, adjust the screw until you get a good sound. Needs oil I’m sure. Get some books before you do much to the car. The red Les Andrews book is a must. You may already have it. The key thing is, was everything working when it was put to bed? If so, don’t change anything. The horn is just a motor. You can fix what is wrong, if anything.
 
The horn works regardless of whether the key is on, so the ammeter movement you observed is normal and would seem to indicate that the wiring between the horn and the rest of the car is OK. The yellow wire provides power all the time. The blue wire routes to the horn rod; when the horn button is pushed, it closes the circuit, thus causing the horn motor to turn and sound the horn.

If the ammeter is only deflecting when you push the button, that at least means the power input isn't grounding to the frame, so that's good (that's a common problem).

You can test the horn while in the car by disconnecting the horn from the car battery and then simply connecting leads to each terminal.
 
Sometimes it is just a matter of getting it spinning again after a long rest. With the cover off and the horn button pushed take your finger and give the armature a push to get it moving. Often that is all it takes. Also if you do get it to spin, place a small piece of fine grade sand paper against the area the brushes contact the armature to clean it up. Doesn't take much.
Your adjustment screw can be very sensitive. Usually only takes a few clicks one way or another to adjust the horn.
Don't be too aggressive in tightening down the horn cover screw. Too tight can affect how the horn works.
 
I doubt the horn is dead, probably just sleeping. Crosscut has good suggestions. I would only add before you do anything just back the adjusting screw off two or three clicks, then push the button. That might be enough. If it struggles, then give it nudge with your finger and otherwise follow Crosscut’s advice.

Also, there are Model A clubs all over the world. If you put your location in your sign in profile we might be able to suggest one for you, and I can guarantee they would want to help you.
Let us know what happens.
 
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All the above is good information. I just did the same thing, after putting in a new radiator. I had to back out the adjustment screw.

I don't think it has been mentioned, but there is no need to cut the wires. There are plugs on the ends of the wires inside the horn that insert into two brass clips. Just pull the wires out of the clips. To bench test use alligator clips or other means to attach to the brass clips.
 
nkaminar said:
All the above is good information. I just did the same thing, after putting in a new radiator. I had to back out the adjustment screw.

I don't think it has been mentioned, but there is no need to cut the wires. There are plugs on the ends of the wires inside the horn that insert into two brass clips. Just pull the wires out of the clips. To bench test use alligator clips or other means to attach to the brass clips.
Click to expand...

Good point.
 
Thanks to all that replied.....

I backed of the adjuster, cleaned up all the armature surfaces with sandpaper, oiled the shaft and worked it back and forth, and lo and behold the horn motor did indeed come to life!! I screwed in the adjuster for a light feel and the horn works. But, it is a steady tone and not the "aooga" sound, so some research on tuning the horn I suppose..... The wires were cut probably decades ago, not sure why..... So at least the horn now works and I will sleep tonight!! Thanks again to all who left advice.....
 
HEY>>>
Before you get rid of the car...
We'd love to see some pics of your father's 31" coupe
 

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Very nice! And a coupe without a rumble seat! Don’t change that out! A trunk is much more useful. :) Even with a trunk.
 
Nice car.

Glad you got the horn spinning again. To adjust just go one click of the adjuster at a time. You will get it sounding good.
 
The horn , generally, will sound different with the motor running, charging the battery, then when just pressing the horn button with the motor off. I always start my car , rev up the motor slightly, then do the final adjustment on the sound of the horn.
 
To not have a steady tone,push the button when it gets up to speed let off it when it stops push it again.It has an electric motor that changes tone with speed of the horn motor not like a vibrating horn.If your battery is low it will affect it too.
 
I’ve found the oil gets stiff. I’ll squirt some kroil in the bearings with light oil as a follow up. Also slightly corroded or filmed over electrical connections will cause a voltage drop. Even a crappy connection where the bullet connectors attach to the brass clips. You may have to take the horn apart to clean the connections on the brushes. If you do, some horns have a reverse threaded screw. You’ll need to verify your horn, if you go that far.
 
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