Not so great sounding horn

Dan Baron

Dan Baron

Senior Member
I have a great sounding horn when the my 1930 coupe is running. But if the lights are on, the horn doesn't sound as good. My question is: Is this normal? Is the alternator capable of supplying enough current to more than 1 thing at a time? or is there something wrong with my alternator? When it's running it sure seems to be charging well enough, probably a little too much, but I don't drive too far, so I want it to charge the battery quicker. Thanks....
 
Do you have the original generator, with the little cutout box on top, or do you have a modern alternator fitted to the car? If you have the original generator, then that is normal. If it charges too much, you can adjust the third brush to cut down the output. The Service Bulletins explain how to do that. If you have a modern alternator, there should be no difference if the lights are on or not.
 
Agood test for the horn: will is operate good with out the engine running ?
Often times you can remove the bell, clean and lubercate the the wheel the runs on the diaphrame .
 
Don,you must be thinking of a one wire horn.The A horn grounds through the button,right?I have found a good way to check the ground is to clip a jumper to the lead going out,(to the button) and scratch the other end on a head nut.If you get a good noise that way but not with the button start looking at the contacts in the button,too much paint between the column components,rust,etc.I have one that needs a drop of oil every so often.I have two others that I have never even looked at in all the years I have had them.They just work all the time.Those are on unmolested cars that have never been apart.
 
It's got nothing to do with the generator. Horns draw a lot of current. The battery honks the horn. The generator just recharges the battery. All accessories on the car should work fine even with the engine off.

What you've got is a bad connection between the starter and the cutout (which is where the horn and headlight circuits separate). So follow the current: The horn works fine without the headlights, so can't be the horn switch. The headlights work, so it's not between the headlight switch and the headlights. That leaves the connections at the starter, junction box, ammeter, and cutout. Check for loose or corroded crimp connectors. Often, you can't see the corrosion because it's inside the crimp.

You can locate which one is the culprit with a voltmeter. With the engine off, ground one lead of the meter and turn on the headlights. Beginning with the starter, touch the other lead of the voltmeter first to the upstream then the downstream side of each connection while someone honks the horn. When you find one where the voltage drops more on the downstream side than the upstream, replace that connection. There may be more than one bad connection in that section of the wiring, so check them all.
 
A well oiled and adjusted horn should draw about 5 amps. Original headlights and tail light draw about 8 amps. Both are connectec to the output terminal of the cutout, so when the lights are on and you blow the horn some of the current comming from the battery will be less for the horn. The horn should still blow good though if it's working right and oiled. Since the model A didn't come with a voltage regulator you probably have the third brush set for about 5 amps, which I consider too much. When the lights are on you are supposed to remove the generator band and set the third brush up for more charge so you don't drain the battery. This will also make the horn blow better.

Since most people don't bother adjusting the third brush each time the lights are turned on or off, the best thing you can do is install an electronic voltage regulator. Then your horn should also blow better, because when the horn button is pushed, the generator output will increase to meet the added demand.

My generator with my EVR stays right near 0 on the amp guage. The only time it reads more amps is right after starting when it goes to about 6 to 8 amps for a minute or so then tapers down to about 0 to 1 amp again.

Having an EVR is good for the generator and battery life. It also lowers the pull on the belt and engine. I have an excercise bike with a Model A generator mounted with an EVR in it. When you turn on the fan, which draws 5 amps, you will realise how much extra pull the generator makes for the belt and engine when it's constantly putting out 5 amps. An EVR gets the charge back to near zero when the battery is charged and the extra power isn't needed.
 
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