Technical ** fixed**Getting shocked when hitting the horn. 41 Ford

1941 Ford convertible in the shop and they are complaining that when you hit the horn and touch your arm to the Chrome garnish moldings you get shocked. Sure enough it happens. Everything in the horn ****on ***embly is stock and in good order. The relay the horn all that stuff is good too. Is it just because the horn ****on is metal? It's got 12 volts at the horn ring and when you depress it nothing because it grounds. Any thoughts anybody?

 

I can't solve the riddle, but keep in mind horns are usually hot all the time, so I would disconnect the battery until you figger it out.

 

A shock from 12-volt is odd. You can touch a car battery on both terminals and not get shocked. But I also know not to lick a 9-volt battery. lol
I would guess the relay is wired wrong or faulty.

 

@550Coupe has the exact car and had the exact same problem several years ago, maybe he'll chime in of what he did to fix it

 

Sweet I'll wait to hear from you. I've wired the relay different ways and it doesn't matter it either works and you get shocked or doesn't work

 

Obviously it's a ground problem. If you are getting shocked, it's because YOU have become the ground...I suspect a poor (or no) body ground strap.

 

You can hit the horn ring and the horn Works without you touching anything else just fine but if you touch the garnish molding or a ground with your other arm you get shocked

 

I wasn't able to find a detailed schematic (for free), but I would venture a guess.

Attached is the best I can tell your horn ***embly is wired from reading some free schematics (please forgive the crudeness of the drawing).


1. The horn ****on provides a ground for the coil within the horn relay (one wire)
Press the horn, relay coil has a complete path, energizes, contacts are pulled in, and then sends 12v to the horn)s)
2. The 2nd wire to the horn relay is 12V from the regulator
3. The third wire(s) go to the horns(s)

I think it is a possibility that the wire from the horn to the horn relay and the 12V are reversed (thus pathing 12V to the horn ****on). Secondly I would wonder if the internals of the physical horn ***embly correct.
Just some thinking points.
don

 

Are one of the coils in the system back feeding a higher voltage? Just thinking out loud I can’t imagine getting shocked from 12 volts.
Maybe @Crazy Steve has an idea!
Dan

 

I've gotten shocked on the horn ground wire too, I think if you make and break the circuit fast enough; it's pulsating DC, which can shock you. Try opening and closing the points with your finger and you will see what I mean.

 

I would think that the column has a poor ground and your a better one leaning on the arm rest

 

The column Mast is bolted to the steering box which is bolted to the frame so I figured there's a good ground there. There's an aftermarket turn signal switch on the column that lights up so there's a good ground on that.

 

I don't know if auto relays have a suppression diode installed inside, but it won't hurt to put one across the coil,(reverse biased) like this




-.
It suppresses back EMF, this is what you may be feeling as it is on the coil side (switched low current) of the circuit. I would use something like a 1N4004 (1 amp, 400v) diode.

 

Steering shaft is not grounded properly.
Horn relay act as a voltage transformer.
Had this happen when i rebuild steering box and put in good fresh thick oil/grease mix.
Maybe adding another relay between horn relay and horn ****on would help.

 

Yeah, check the grounding. Use an ohmmeter, check between the ground post on the battery and the horn ring/steering shaft/column shell, if you have more than a few tenths of an ohm it's a grounding issue. Hot rodders don't like bare metal, electricity doesn't like paint. If the garnish molding was painted, you likely wouldn't feel a thing. You don't say if this is an OEM steering box/column or an aftermarket unit. That can make a difference, especially if a rag joint is used on the steering shaft.

 

Is this a new build, or a car/horn that's worked fine until now?

-rick

 

The horn ****on should be switching the negative to the relay. It shouldn't be switching the positive.

 

The horn contains an electromagnet and points that interrupt current through it after it has caused enough movement, making thing spring back, points reconnect and the electromagnet moves things again.
A coil that is controlled by points and produces shocks, does that sound familiar to anyone? Yup, same principle as an ignition coil, when you interrupt the current through a coil it produces a high voltage spike in an attempt to keep the current flowing - coils hate changes in the current running through them.

I'm guessing you are feeling those voltage spikes. Perhaps due to poor ground connection.

 

I wear along sleeve shirt. I've had the car since I got out of high school (1962). Maybe some day I'll fix it.

 

550 coupe hahaha. Customer's car they just bought from out of state sight unseen. Basically a stock car ,drivetrain and all.may go in Sunday and mess with it

 

So dumb question, but after being repeatedly lit up by my 59 while trying to re***emble the horn ****on after replacing the turn signal switch, is the plastic insulator under the ****on there, or complete? If its missing or cracked, I could easily see the horn ****on becoming live, and being that the steering wheel itself likely insulates it, you become the next best path to ground.....

 

My 47 Ford did the same thing. But check and I'll bet you are getting shocked when you let up on the horn. The problem is the coil in the relay. When you let up on the horn, the magnetic field around the relay coil collapses. So you end up with a collapsing magnetic field around a coil of wire. Sound familiar? That's what goes on inside an ignition coil. In a horn relay you can get a 60+ volt spike as the field collapses. It is trying to find a path to ground and your arm on the garnish molding is a good path. The fix is a suppressed relay; one that has either a resistor or a diode across the relay coil. When we first started putting a lot of electronics on heavy trucks, we ran into problems with relays and the voltage spikes when they were turned off. Electronic controls do not like voltage spikes. The first fix was a relay with a diode across the coil. That worked, but you had to insure that the relay coil energizing wires had the correct polarity or you would blow the diode when the relay was energised the first time. Later we switched to relays with a high value resistor across the coil and didn't have to worry about coil polarity.

 

Any part numbers? Gonna start searching now

 

here is a bosch unit. 5 pin, pay attention to the schematic in the pic, it has the triangle diode symbol across the coil (85-86) that contains flyback current.

The coil must be wired correctly-the ones without the diode work either direction, but these wont. The hot trigger wire has to go to pin 86, and 85 goes to ground.

Bosch Automotive 0986AH0135 Bosch Relays | Summit Racing

oreillys doesn't list diode/nodiode, but other local parts stores might.

Its more of an OEM type thing if you can get the part number.

I'm sure Amazon probably has them pretty quick. I bet an auto electric shop or Stealership could get you one same day.

-rick

 

I got that one and another coming,we'll see how it goes

 

Haven’t read all the post, my Chevy was doing the same. I have a three post relay and had the signal wire one to column and the hot wire switched. So instead of completing the ground at the horn ring I was completing the hot and it would light you up. Horn worked both ways

 

I’m not understanding why positive 12V is being mentioned as being switched so often. Guess my real question is, are we talking positive ground or negative ground vehicles? Both types have been mentioned on this thread.

 

This car is 12 volt negative ground

 

Reread your opening question. “12V at horn ring”. So what’s to feed back from. Did you get that via a multimeter? Will a test light light up if you probe the ring?

 

Yes I had a voltmeter positive to the horn ring and the negative to the garnish molding and got 12 volts. When I depressed the horn ring 0 volts. I did not hook up a test light to it