VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 '31 Horn Restoration

I've got a '31 pancake horn that is disassembled. I've looked through the forum and on the '31 Chevy webpage looking for instructions on how to assemble these horns from scratch. I found a few forum posts about parts of the process, but nothing comprehensive for someone that is ignorant of the process. Does anyone know of a resource for doing this. I want to fix it myself and not send it off.

Thanks,
Brandon

Don't know of any complete instructions on assembling the '31 horn. I will try to give some basic instructions.

There are two critical areas that need to be checked first. The electromagnetic coil must be good. It can be checked with a VOM or test light for continuity and lack of grounding. Checking the path between the studs and studs to ground can do it. The other is the switch contacts. The contacts need to be clean and not grounded. There needs to be an insulating pad on top of the switch. You can check the switch operation by pushing down on the pad. Of course the two studs need to be insulated from the body and not grounded.

Once the parts check out then you can begin to assemble the horn. There are six small carriage bolts that hold it together. Three bolts hold the vibrator plate, reinforcing ring to the body. Originally a paper gasket was installed between the parts. Many times it will be missing. Be sure to locate the short stud over the switch. Movement of the plate operates the switch. If the center stud has not been disturbed then leave it alone. If it has been disturbed an adjustment will need to be made. That adjustment can be problematical. Basically the center stud needs to have a little space between it and the center of the electromagnet so that the plate can be drawn down a little toward the magnet. That movement breaks the switch contact. The make/break is what causes the plate to vibrate. The final adjustment is the small slotted stud, with jam nut that comes through the body and contacts the switch. If you adjust the stud so that it just breaks the switch contact (measure with VOM or test light or just play with it) and then back off a 1/4 turn or less. The horn should work. The tone may not be what you want. If not you can now adjust both stud and center stud to produce the most objectionable and loud sound possible.

I've got several pictures that may help. I took them while disassembling my '31 horns. Send me a pm with your email address if you want them.

Happy Motoring!
-Bill

There is a guy in upstate ny that's all he does is rebuild horns. If you call him he would be more than happy to help you with your concerns.

Thanks Chipper. I took pictures when I took it apart but I'm not sure what all the parts are. I'll try to print out what you wrote and read it as I look at the parts to see if I can figure it out.

I think you should be able to get it back together if my instructions are clear enough. If not get back and ask as specific questions or post photos.

Curious. How loud should the pancake horn be? Mine works but has a low tone. I've tried adjusting it but it's not very loud and often in pictures I see cars with other horns under the hood. Is this because the pancake simply failed or is this because the Pancake horn is not really that loud. How many decibels does the average one blow? That might help me determine. Possibly Chipper's info might help me get more volume out of mine.

As a guess I would say 100 db or so. They are very objectionable when working right. You probably need to make little larger gap between center adjustment bolt and center of electromagnet. Adding another thin paper gasket on both sides of the vibrating disc might also help. Helps to seal out water too.

will check it out. Probably no paper gaskets anyway. It had been chromed and assembled when I got it so I never touched it other than try to adjust it. I'll have to investigate it more as mine wouldn't get the attention of a mouse! LOL

Chipper is right. They are really loud when tuned. I've got two, low and high. When I tested them, I thought it would make me deaf!

Well, following Chipper's instructions, I went at my horn. Turn out the PO when he worked on it, he had backed out the center adjustment. Working with paper gaskets, and both adjustment, I got my horn to sound pretty obnoxious!
One small piece of advice that Chipper left out. Bolt the horn back together with all six bolts when making adjustment. If you use just the three and make the adjustments, it will not work correctly all bolted up. I originally did it with just the three and when it went back together, nothing. Did it with the six bolts and it worked the second time I put it back together. Yup, I realized I still needed to back out just a bit more on the center adjustment bolt so when it went back together, it worked fine.
So with that said: use six bolts all tight and the paper gaskets. Then when you get it to sound really good, turn the center screw out (CC)another 1/8th turn. Then put the trim ring back on. At least that worked for me.

Glad you got it working better. The adjustments are not difficult if you understand how the horn works.

Not hard at all. Once I added the paper gaskets and turned the center bolt in all it took was a little turn here, a little turn there. LOL The center bolt was out to the point that the end was recessed over a 1/16 into the vibrator body so it was not even close to make contact with the center of the coil/magnet. You and Bill are right, these damn things are loud. I had no idea and thought it was just the way it was. Now I feel a little better knowing I have a horn that stupid drivers will hear.