VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 '31 Pancake Horn not sounding

I have an original nice '31 pancake horn, but cannot get any sound. Seems to be a problem getting the circuit to close. When I connect the terminals to pos and neg can't get any volt reading across the terminals.

I've checked the internals and everything looks complete, re-built the terminals themselves with new bakelite type insolators etc. The contact points are cleaned up and filed/sanded smooth fit, and both of the adjustment screws/nuts freed up.

Is there a simple procedure to get these ringing? Can someone explain just how the electricity passes through one of these to power up the electromagnet etc. I hate to put an aftermarket one on if I cannot get this one working.

It could be that the contacts inside the steering column are broke.

A way to try this is to get a battery (6 or 12V) and two bits of wire, put one end of each into each terminal on the horn and hold to the corresponding terminals on the battery.

Have you tried the adjustment screw because if it screwed in too much the horn wont sound.

Dan

Hello Gunsmoke,
I googled 'how does a horn work' and clicked onto 'secondchancegarage.com' for info. It appears that it takes lots of current to power horns. Just like the starter relay is needed for modern starters, a relay is needed between low current horn button and high current horn. They did not discuss horn adjustment procedures, that'll take a different search. I believe that you can do a bench check with a battery and fused positive lead wire for safety. If I recall correctly, the adjustment screw needs precise adjustment to dial in the sound properly. The locking nut can change the adjustment if the screw is not held firmly enough. I do not know if the horn is marked pos and neg, or if horns work with the wires crossed. Good Luck. PS. Tell us what glue/adhesive is recommended to bond the aluminum cap strip to the aluminum roof trim that you're having made.

A horn relay was not used in 1931.

Hello J Y D,
Thanks for the correction about a horn relay not used in '31.
Hello Gunsmoke,
I got to thinking about benchchecking a horn and it may require two ground wires to operate, one from battery negative to the ground terminal and one from battery negative to ground the horn body. Don't know for sure but worth a try.

The vibrator type horns used in the 30s use a few simple parts. First a wavy vibrator disc with thicker steel disc and a pin spot welded to the back side. Most have secondary disc held by a center bolt and lock nut. The center bolt can be adjusted to change the tone. It should be adjusted initially so the center bolt is close but does not contact the electromagnet. Next is an electromagnet that pulls on the thicker steel disc to pull down on the vibrator. A set of points that align with the pin on the vibrator to open when the electromagnet pulls the steel disc down and close when the electromagnet releases the vibrator disc. Finally a slotted head screw and lock nut that adjusts the point assembly. It is the oscillation of the vibrator disc that makes the sound.

If the points are clean, top of the point assembly (where the pin contacts) insulated, coil of wire around the electromagnet and other connections good the horn can be adjusted to work. The easiest way to do the initial adjustment is to use a VOM or test light. Set the adjustment screw so turning in a teensy bit will break the points and open the circuit. Apply power and fine tune the adjustment to produce the desired sound. It is not necessary to have all the bolts holding the vibrator plate and cover in place. In fact it is best to not have the cover on as it gives access to the center bolt and that adjustment if the initial setting does not produce an obnoxious tone.

The only wires required are a positive and negative wire from the battery. One can be clipped or attached to one horn terminal. The other will be swiped past the other post to check and see if there is a spark and at the same time noise. If you get a spark and no noise something that should not be grounded IS or your adjustment is too far off. I have rebuilt a number of '31 and '32 horns over the years. It can be frustrating but rewarding to bring them back to life.

I used my 6v battery charger to test my '31 pancakes while I was renovating them; it worked great. Chip's tuning instructions are right on.

Thanks for all the tips/advice. Connected + wire to a terminal and there is no spark when second terminal is touched/grounded leading me to conclude there is an open point somewhere in the circuitry. I will proceed to check for the various possibilities suggested above. Only area I don't know where to look for an issue is the electromagnet itself. If it were to have a break of some sort I assume that would kill the horn.

p.s. expect to pickup the roof molding tomorrow, will keep you posted in that topic.

A break in the winding for the electromagnet coil requires rewinding unless it is one of the exposed ends. There are places that can rewind but not cheap. Fortunately breaks in the wound part of the coil are rare. Bad connections are more common.

The horn shop just rebuilt mine. Located in Rome NY. Jmm

NITMOI! A friend had a Sparks-Withington bugle style horn he gave me to use in place of mine. The 12" trumpet was secured to that horn with a chrome faced piece of identical diameter and screw spacing as the Chevy Pancake. Soooo, I removed the trumpet and face plate from that horn, and fastened on the Chevy face plate, made a new mounting bracket, and I am in business. I will explore the original over the winter. The S-W horn needs to be grounded, so it is obviously a bit different. I am wondering as well if it may need a relay. Don't expect to use the horn much, but will check this out (unless one of you knows!)

Hello Gunsmoke,
SOUNDS like you've got your horn worked out. Chipper said that all that's required is a pos and a neg wire to work. That being the case, the point contacts (must) be in contact when the horn is off, so that there will be continuity awaiting power. Then, when power is applied, the electromagnet energizes and disconnects the contacts. The contacts being part of a diaphram, make sound, opening and closing rapidly. I hope that's right. If not, you can always yell 'aah-ooo-gah'. Cheers