Very strange issue with my horn 1940 buick

[Robby120113]

Hey guys 
 

since i had the car the horn ring didnt work and a alternative button was mounted on the dash. Now i installed a new wireharnes in the car and also the cable in the steeringtube is replaced. 
now here is the issue. The horn ring works great again. But after a 20 minutes or so the car starts to horn. I then have to quickle run to the garaga and removed the cable from the steering housing. Nothing is touching the car whats so ever. Then the next day i can reattach the cable and all works again. Then after a 20 minutes without warning it starts to horn again on its own. Im confused. Is there some kind of voltage build up and need to discharge?  So better i do not drive with the cable attached at this moment. Car is a 1940 buick special model 41

Edited April 26, 2021 by Robby120113 (see edit history)

[Robby120113]

Maybe i have found something. The membrane that holds the spring was partially gone. Now maybe the spring can cause the shortage between the 2 parts of the steeringwheel. I wrapped the lower bit of the spring in shrink wrap. 

[Buicknutty]

Sounds like the likely culprit to me. Hope it's fixed!

[1937 Buick 66C]

I concur;  This looks like the likely problem.  When these deteriorate enough, they don't insulate well.  Something as innocuous as a change in temperature can cause contact to occur.  Since this is low current (only enough to trigger the relay), you may not see any evidence of arcing what would definitively identify the deteriorated insulator as the root cause.

[Terry Stock]

One night at 0200 the horn of our '39 went off.  Not much fun.

I had replaced the old rubber insulation already.  I suspect a bit of moisture making the connection.

After that I installed a battery switch and after arrival back home, the routine is to switch off the battery.

[JohnD1956]

On 4/26/2021 at 2:46 PM, Robby120113 said:

Maybe i have found something. The membrane that holds the spring was partially gone. Now maybe the spring can cause the shortage between the 2 parts of the steeringwheel. I wrapped the lower bit of the spring in shrink wrap. 

I dont have any wiring diagram for a 41 but I believe this circuit would be hot (active) all the time.  And that spring is pretty wide so as to not connect to the lead coming up through the column.  It would seem to me that for the membrane to be this problem it would have to suddenly collapse after 20 minutes and then somehow rejuvenate after the power is cut from the system and that seems unlikely. Given the state of that membrane if it collapsed once I doubt it would return at all. 

And given the symptom that the horn blows after 20 minutes each time, then it seems likely that somewhere else there is excess power present in the horn wiring and compromising the wiring (a short circuit). 

 

What does the insulator,at the steering wheel end of the wire in the column, look like?  Is that melted? And does your car use the brass ring on the lower end of the steering column for the horn connection? There should be an insulator under that brass ring. Is that still intact? 

 

If that horn button is the problem I might be tempted to leave it off the wheel and then see if the horn does not blow after 20 min or a half hour while standing guard with fire extinguisher and an infared thermometer to test the temperature of the steering column wire and horn connection wire.  And if either show evidence of heating then  I would suggest looking for a short somewhere.