Original Model A horn

[ldreeg]

My Stewart Warner horn only blows 2 notes, can't get the Gaa. I've had it apart several times and replaced the diaphragm, sent it to a local "expert" and it came back worse than before. I changed out the diaphragm again but still only 2 notes. Very frustrating. It is fully restored and the motor spins great when you back off the adjustment screw.

What else can I do?

[Jeff/Illinois]

What I did on our Roadster was carefully pack away the original horn, and bought a 'new' one mfg. by A&L, thru Snyder's.

It is a perfect copy of the original, down to the Sparks-Whitington tag riveted on the can, and man does that baby sound out!!

Sorry that doesn't answer your question, sounds like you have done all the relevant fixes, but I sure love our Snyder's Sparton horn! Plus nobody knows the difference AND if it were to sprout legs and disappear like they have sometimes been known to do you aren't out an ORIGINAL horn

[ldreeg]

Thank you for that, I used to have one on this car before. It's on a Fine Point car so I sold the reproduction. I need to get this one working correctly.

[Charlie Stephens]

Are you running it on 12 volts?

Charlie Stephens

[ldreeg]

6 Volt positive ground. I've tested it off the car with a fully charged battery.

[mcgarrett]

Sponsored Links (Register now to hide all advertisements)

I had a similar problem and found that the adjustment screw was very sensitive. By that I mean that I could barely move it right or left to make a noticeable difference in the sound. I'm assuming that mine is suffering from worn parts and yours may be too, but with some fiddling, I finally got it to sound pretty good.

[alexiskai]

Originally Posted by ldreeg

6 Volt positive ground. I've tested it off the car with a fully charged battery.

Just to be clear, when you tested it off the car, it produced the same incorrect sound?

[mcgarrett]

You mentioned that you replaced the diaphragm. Did you inspect the diaphragm ratchet and ratchet tension spring for wear or damage? A new diaphragm alone won't cure the problem if those or perhaps other parts are worn or damaged.

[ldreeg]

Originally Posted by alexiskai

Just to be clear, when you tested it off the car, it produced the same incorrect sound?

Yes, Same on or off the car.

[ldreeg]

Originally Posted by mcgarrett

You mentioned that you replaced the diaphragm. Did you inspect the diaphragm ratchet and ratchet tension spring for wear or damage? A new diaphragm alone won't cure the problem if those or perhaps other parts are worn or damaged.

Yes, I've replaced the diaphragm multiple times with reproduction and original. replaced the ratchet multiple times and spring is good. Still no 3rd note.

[alexiskai]

I actually had a very similar problem with my S-W horn and it came down to the fact that the S-W and Sparton horns use different adjustment screw setups. The S-W screw is longer, and the bridge for it has the serrations cut into the bridge, while the Sparton screw is shorter and uses a smooth bridge, with serrations cut into a clip that goes over the bridge.

Most reproduction parts are based on the Sparton horn, so if yours was restored using Sparton parts, that could explain the problem. You might try to find a donor S-W horn to steal the adjustment screw assembly from; however, these tend to be the first parts to go since they are exposed to the outside.

I ultimately solved the problem on my horn by using the Sparton bridge setup with the original S-W screw. It might also work the other way around, I don't know. Using the longer screw allowed me to get the proper pressure on the ratchet to produce the right sound.

[rotorwrench]

The armature or field coils could have age related problems. The fields can be checked with an Ohm meter. The armature can also be checked for dead spots or shorts but the way the horns are put together, checks can be somewhat limited. There are still a few folks out there that can overhaul the little armatures. Jim Diehl is still vendor listed on the MAFCA site. The fields aren't all that difficult to rewind with the proper amount of magnet wire and some new insulator material to replace the often deteriorated fiber board. There are procedures out there if a person want's to rewind or change to 12-volt. Brushes are available.

These little motors are all shunt wound field types to give them a little more start up strength with no polarity issues. Pulling that ratchet wheel over the diaphragm nub isn't bad once it's moving but it takes more current to get it moving. Make sure the nub aligns with the ratchet wheel. Not all horns have an index for it. A person can put some lubricant on it as long as they don't get carried away with it or it'll sling all over in there. The oiler wicks for the armature bearings only need a drop or two of light oil or they will become dirt magnets. Both ratchet tension pieces (front and rear adjuster bar) also need a little bit of grease on the contact surfaces with the armature. Make sure the armature has some air gap with the pole shoes. Rubbing will slow it down. Too much air gap may also slow it down so note the air gap if ever reworking the fields.

[ldreeg]

No reproduction parts except the diaphragm, which has now been replaced. everything else is original.

[ldreeg]

Originally Posted by rotorwrench

The armature of field coils could have age relater problems. The fields can be checked with an Ohm meter. The armature can also be checked for dead spots or shorts but the way the horns are put together, checks can be somewhat limited. There are still a few folks out there that can overhaul the little armatures. Jim Diehl is still vendor listed on the MAFCA site. The fields aren't all that difficult to rewind with the proper amount of magnet wire and some new insulator material to replace the often deteriorated fiber board. There are procedures out there if a person want's to rewind or change to 12-volt. Brushes are available.

These little motors are were all shunt wound field types to give them a little more start up strength with no polarity issues. Pulling that ratchet wheel over the diaphragm nub isn't bad once it's moving but it takes a more of current to get it moving. Make sure the nub aligns with the ratchet wheel. Not all horns have an index for it. A person can put some lubricant on it s long as they don't get carries away with it or it'll sling all over in there. The oiler wicks for the armature bearings only need a drop or two of light oil or they will become dirt magnets.

Here is what was done be a local "expert":
Replaced diaphragm, terminal block terminals, wavy washer under ratchet nut, carbon brushes and springs. Also reflowed solder joints.

I guess I need to contact Jim Diehl!

[ldreeg]

Just spoke to Jim's son and he's not taking any new horns at this time.

[alexiskai]

Can you post a picture of the motor, with focus on the adjustment end? Maybe someone will spot something off.

[ldreeg]

Originally Posted by alexiskai

Can you post a picture of the motor, with focus on the adjustment end? Maybe someone will spot something off.

Here you go!

[alexiskai]

OK, and what is the change in behavior for the horn as you back off the screw?

[ldreeg]

Originally Posted by alexiskai

OK, and what is the change in behavior for the horn as you back off the screw?

After a few turns, it spins freely.

[alexiskai]

Originally Posted by ldreeg

After a few turns, it spins freely.

So it goes straight from "no contact on the diaphragm" to "ahooo" to "buzz" and there's no sweet spot where you get the right sound?