1951 Mercury 12 Volt Conversion Horn Problem

H

Henry Ford IV

Member
Hi, Just got a 51 Mercury that has been converted to 12 volts. Lots of things weren't, gauges, overdrive and horn. It seems like the wire that comes off the horn button to the relay is hot and should be a ground. Logical since the 6 volt was positive ground now the 12 volt is negative ground. Anyway, I am trying to access the horn wire. I am betting that it picks up voltage from the junction block. If I could get to the junction block I could free it from the block. Or, I could intercept it when it comes out of the steering box before it goes into the junction block. Which is easier? It seems like I will have to disassemble the car to get to the junction block. I haven't crawled all the way under but I don't know if I can see it coming out of the steering box. Any advice? I assume someone has done this before.
 
The mid century Mercury cars have a different steering gear than the Fords of 49 thru 51. The wiring internal to the column runs down a conduit in the jacket. It exits on the left side just below the dash. There is a terminal block that hangs there from a wire. All of the turn signal, horn, and brake light connections go to that terminal block first. I'm away from my books and diagrams right now but I think VanPelt Sales has the diagram on his website.

Ground is still ground if polarity is switched. Gauges and the ignition coil are affected. All the light bulbs are affected. The generator and regulator of course. The OD operating solenoid should be OK. Relays are affected but 12-volt replacements are available. The starter will.work but the old style bendix may not take well to the excess torque output. Horns get real loud and raspy on 12-volts but there may be a way to rewind them to a 12-volt configuration for the vib coil. The old 2-speed heater motor may be problematic but I don't know. My 51 cars are still 6-volt.
 
The horn circuit should have battery voltage for its entire length. On both sides of the actual horn, and all the way to the horn button. The horn button is just a momentary switch to ground.
To test, disconnect one wire on the horn. If both terminals on the horn have battery voltage you have disconnected the wire going to the horn button. If both terminals on the horn have zero voltage you have disconnected the supply wire.
When I changed from 6 volt positive ground to 12 volt negative ground I did not do anything to the horn circuit. It did blow an 8 amp fuse so I put a fatter one in. I haven't touched it for 30 years. This was on a '46.
 
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Thanks guys, I'll work on it today. Restating the problem, there are three terminals at the relay. B S and H. I get voltage at B and voltage at S. If I leave S unconnected I can ground it off the battery and the horn blows. The problem is I have voltage at S. It should be a ground.
 
All those old Ford horn relays are marked the same. H=horn, S= switch, and B=battery on the horn relay. The horn is ground activated but the S terminal is part of the switch circuit so it's hot at the relay where it controls the relay contact coil but it doesn't have a ground yet. If you ground that S terminal then the circuit is closed and the horn should sound unless the horn vibrtr circuit has a problem. The horn ring controls the switch to ground that activates the relay. The relay is always fairly close to the horns so that they have less wire resistance in the horn sounding circuit or vibrtr circuit if you will.

Forgive me for taking the vowels out of the vibrtr term. If I spell it out it is blotted out due to the term being considered vulgar by the thought police who dictate the algorithm that redacts such words. I could use v!brator but some are confused by the exclamation point.

I had to completely rewire my 1951 cars due to deterioration of the wiring. An FYI: I had to fabricate a tool that I could work into the female socket on the terminal blocks to get the male bullet pins to release. You will find that they don't want to come out unless you do that. The female socket have an open seam where I work the Tool in there to expand the loop that forms the socket bore.
 
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Problem solved! Thanks, Rotor, I am so stupid. I had to read what you wrote 3 times before it sunk in. The S terminal is hot. That is what was throwing me. I saw the S terminal was hot and for some reason I thought the wire from the horn was hot. Its not, I just checked it. That and a blown relay, I hooked up my new one and the horn blows. Wow! At least I didn't rip the whole car apart looking for what? I don't know.
 
Henry Ford IV said:
Problem solved! Thanks, Rotor, I am so stupid. I had to read what you wrote 3 times before it sunk in. The S terminal is hot. That is what was throwing me. I saw the S terminal was hot and for some reason I thought the wire from the horn was hot. Its not, I just checked it. That and a blown relay, I hooked up my new one and the horn blows. Wow! At least I didn't rip the whole car apart looking for what? I don't know.
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i had a similar problem and was often frustrated that my horn didn't work when driving around town. it seemed that every two seconds some inconsiderate driver warranted a good, "honking at".

and then when i did get it fixed, it appeared that it also removed all the rude drivers from the road! now i'm hankering to blast someone, and can't find a deserving candidate... politely "tooting" at kids and admirers on the sidewalk just isn't cutting it...i want to really BLAST someone! :)
 
hueyhoolihan said:
i had a similar problem and was often frustrated that my horn didn't work when driving around town. it seemed that every two seconds some inconsiderate driver warranted a good, "honking at".

and then when i did get it fixed, it appeared that it also removed all the rude drivers from the road! now i'm hankering to blast someone, and can't find a deserving candidate... politely "tooting" at kids and admirers on the sidewalk just isn't cutting it...i want to really BLAST someone! :)
Click to expand...

I enjoy your perspectives Huey!
 
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