I have a 1931 Chevrolet that is all stock except a 6 volt alternator and LED taillight. I have restored an original pancake horn. The horn works when connected straight to the battery with jumper wires, but will not work when attached to the regular horn wiring. (I am familiar with how to adjust a horn, so I know this is not the problem). A) tested the hot wire to the horn to make sure it has power (6 volts) B) tested the voltage between the hot and ground wires, when the horn button is pushed, that go to the horn (6 volts) C) tested the continuity of the ground wire when horn button is pushed (yes continuity) D) tested the electromagnetic coil of the horn (.40 ohms, good) E) jumper wire straight to car battery and grounded to the car frame (Electromagnet functions properly) It seems that even though the horn wire is showing a full 6 volts, it still won't activate the electromagnet in the horn. Is it possible that the wire will support 6 volts, but when put under the load of attempting to use the horn, it won't support the full 6 volts? I'm not very educated on the principals of electricity, so I'm a bit lost here. Thanks, Brandon
i would guess it is not getting a good enough ground at the button. make sure all the contacts are clean and the column is grounded. if you ground the wire at the connection to the column does it operate the horn correctly [basically bypassing the horn button to test my theory]
That is a good idea. I can hook the horn up to the hot wire on the horn wire and then use a jumper wire to ground the other side. If it works I know the problem lies somewhere in the connections inside the column and button. I'll give that a try tomorrow. Thanks!
you shouldn't have to hook a hot wire up, just leave it wired in. there should be a plug where the wire exits the steering column tube. unplug it there and ground the wire from the harness not the column and it should complete the circuit for the horn. that horn should have power all the time to one of the terminals the other runs back to the horn button and is grounded when it is pushed.
Just install a horn relay and be done with it. You really don't want the load going through the column anyway. Use the horn button to ground the relay, very low amps, no load, button and contacts will last for ever.
Yes, that is very possible. "Supporting" 6 volts when there is no load doesn't take much, right? All that is required is continuity. Load carrying requires more than that. While I agree with Joe H above, if you're trying to keep this original and not add any more circuits, than look for places where the wiring may have excessive resistance (assuming that this is the original wiring), i.e. any place where the wires connect to something, terminals or splices, etc. Keep going backwards in the circuit till you find it.
That wouldn't be a 'positive' ground system would it, not that it matters much. When you are testing are you using a digital volt meter? if so you are probably getting false readings as it takes so little voltage to trigger it. Try using a test lamp, connect a bulb & socket where the horn would connect and see if the lamp lights up - it puts a lesser load on the system and will tell you if you are actually getting the full 6 volts.
Use a horn relay.... That horn is drawing at least 15 amps (probably closer to 50 amps if you include the inrush current), that's asking a lot out of the contacts at the horn button. If you have any connections that are even a bit marginal, the current draw could be even higher. It's the voltage drop that's killing your power; an 'extra' resistance of only .1 ohm (below the threshold of measurement for all but lab equipment) will drop 1.5 volt, reducing power to the horn down to only 4.5 volts. You want a minimum of #14 wire feeding that horn, #12 would be better but that still may not clear the issue.
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