Horn won't work
 

I have a horn I picked up at a swap meet about a year ago. It wouldn't turn when power was applied, though it did turn manually. I noticed one wire on the armature was broken, and soldered it back on. Right now I have the motor assembly apart from the projector, and the adjustment screw backed off. There is no contact with the diaphragm, but the pressure arm is still attached and pressing on the ratchet. But it still won't turn! When I attach a couple pigtails to the contacts to complete the circuit and actuate the horn, it makes a slight effort, and might even rotate occasionally and very reluctantly about 1/12 of a turn. I've had it completely apart, and everything is lubed and looks like other horns I've cleaned up and worked on. But obviously I'm missing something.

Not being a strong electrical guy, I don't know what to try next, or what to suspect, or what to look for. Your suggestions? :confused:

Re: Horn won't work
 

Ray, Back the adjuster off if you haven't already. most of what keeps horns working is dirty/loose contacts between the wire connections where the plug in/solder joint, and brushes and brush holders. Use a volt/ohm meter to check for high resistance and poor connections. I've never done it than I can remember, but I'm sure you can take a horn armature and put it on a growler to see if the armature is shorted .

I'm a good electrical guy but I'm sure one of the expert horn guys will chime in.
Check out your connections and hopefully that will cover it!
Best of luck Ray!
Larry

Re: Horn won't work
 

Thanks Larry. The adjuster is way backed off. I cleaned the connections, but I don't know where to take the ohmmeter readings or even how to use my multimeter to do that! :o When I say I don't understand electricity, I ain't just whistlin' Dixie! :p

Re: Horn won't work
 

Try this link. Rod

http://www.groschopp.com/how-to-check-a-motor-armature/

Re: Horn won't work
 

Hi Ray,

Lots of times the commutator just "looks" clean.

After not blowing a functional Model A horn for a spell, I've seen where cleaning out the grooves in the commutator with a toothpick, followed by polishing the commutator with a narrow strip of white loose leaf writing paper can get the horn going ..... also allow the paper strip to slide between brush mating surface & the commutator to clean brush contact area.

Re: Horn won't work
 

Thanks Rod. Good info there.

Re: Horn won't work
 

Make sure the brush holders are not grounded !!!!! Someone may have worked on the horn before and did not replace the insulators on each side of the brush holder ?

Ron

Re: Horn won't work
 

I'll check that, Ron. Thanks.

Re: Horn won't work
 

Make sure the wires and power supply can give you at least 5 to 10 amps at the motor.

With such low ohm readings the motor would have I'd test for voltage instead. The voltage goes through one field coil, then the armature, and then the other field coil, so just grpund one meter lead to the ground terminal of the horn, and move the other lead along the current path to see if the voltage drops off due to dirty brushes or a broken wire.