1952 Pontiac Horns

[MercMontMars]

Hi there, I have a set of Delco Remy 6v electrical horns and I’m trying to get them working. Upon general inspection I can see that the wiring is pretty shot, copper completely exposed and corroded. I can see old wasp nesting inside of the horn. What is the trick to getting these opened up? I can’t see any kind of nut or bolt that’d come off with a regular socket, they all seem to be round besides the hex nut that holds the mounting bracket. Once I do have them opened, what should I do? Not sure what to expect inside of it as I’ve never opened one. Thank you for any help, I’d love to hear these old things go again!

 

 

[TerryB]

Just one of many horn resto videos on YouTube 

 

[Bloo]

Clean the spiderwebs out and un-stick the contact points. Cleaning the points wouldn't hurt. Don't use sandpaper or anything that might leave grit behind. For a light cleaning, drag brake cleaner soaked paper between them. If they are cruddier than that drag a tiny file between them, like a nail file or better yet a point file or a miniature single cut file from the hobby store. One pass oughta do it. Don't try to make the points new, it does more harm than good. Ideally just scrape the oxidation off the high spots.

[roysboystoys]

I think the domed cover is a press fit to the housing Soak with penetrating oil and slowly try to pry between the dome edge and the housing.

The stuff you need to get to is under there.

[m-mman]

Unbolt the bracket, then bend the little tab. THEN the cover can be removed. 

[MercMontMars]

@Bloo @m-mman

 

Thanks for the replies! I used your advice and got them opened up. One looked reasonably clean while the other was completely rusted over. I soaked that one in rust killer as I can’t really damage it much more than what’s been done. I’ve got them both clean, and now I’m down to testing them. I’m testing directly off of a 6v battery and cables, and upon grounding on the horn’s casing and positive to the wire, I can hear a tiny clicking or rattling inside the horn but not much more. Gonna try cleaning the points a bit better as I haven’t done that yet, at least not much more than a slight scraping. How do I know when it’s properly adjusted? I see there is an adjustment nut. 

Edited May 29, 2023 by MercMontMars (see edit history)

[roysboystoys]

Try loosening that nut at the end of the vibrating arm and adjust it slightly up or down, usually helps

There should be a set of contact points under that silver triangle arm I think. If you have a thin point file you can clean it up.

I haven't worked on that style horn, but all I've fixed were similar in design.

[m-mman]

Horns are musical. They are tuned such that the two produce notes that harmonize with each other.

 

 They are a set and sometimes marked “Hi” and “Lo”. If you have ever heard sick horns it’s because one is not working or has been replaced with an identical but not complimentary unit.

 

Mechanics are not piano tuners so there was no effort or tools to test or set a horn’s frequency.  
There is service information from various makes and years that describe how to adjust the note by using an amp meter to determine current draw and adjust the points and nut accordingly.  Check in your shop manual. 
 

Personally, I’ve just cleaned, lubricated and rewired my horns and found that they function appropriately. 

[Bloo]

Yeah, I wouldn't try to adjust it at least not at first. The time might come where you have to.

 

How it works: Huge high-current electromagnet moves diaphragm, but also opens points, shutting off the electromagnet releasing the diaphragm. Diaphragm moves back and points close, electromagnet pulls again, etc. Repeat at a high rate of speed.....

 

The electromagnet draws a lot of current. It is almost like a dead short when the points are stuck. On the other hand if the points are dirty the electromagnet can't really draw enough current to give the diaphragm a good pull and get the honking process started.

 

[dodge28]

Before you do anything , remove the external wires and immerse it in completely for a fer days in Vapor rust. It may look expensive now but you will be happy you did. It will not affect the coil adversely. You may have to drill out the bolts. Punch mark position.    

[MercMontMars]

@dodge28 Thanks for the reply!
Sure I can give that a shot, I’ve heard about some sort of metal diaphragm getting rusted stuck in there so that might help.