Packard Forum Index » Post-War (1946-54)

RE: 2106
Having no luck getting horns to work after engine rebuild and horn disassembly/painting. They worked before.
I think horn assembly is grounded - have continuity from the base of horns (inside the covers) with the head bolts that mount the bracket. Have power to the relay (test light) at the terminal "B".
I understand that the horn switch grounds the circuit, so before I go into the switch, shouldn't I get a honk if I touch the horn wire to ground before it enters the steering box? What am I missing?
Thanks,
Mark

Should work as you describe unless the relay is bad or the horn and bat wires are reversed on the relay. Have you verified the H, S and B terminals on the relay are wired correctly. If they are you should at least hear the relay click when grounding the lead at base of steering box. If you hear relay click but no horns then it is most likely a ground issue or contact adjustment with horns. They require a lot of current so even though you can read continuity it is conceivable paint or something is preventing a good connection that is solid enough for the current needed. If they were disassembled is the contact gap correct and when horn is off and relaxed are contacts touching so the magnet can pull in to start the cycle?

The horn wire grounds the relay to trigger it, which then supplies power to the horn. The horn is grounded via where it is attached to the car.

So, a quick test would be to run a jumper from the battery to the wire terminal on the horn and see if it works. This bypasses the relay. If it works, then the relay or wiring with the relay is the culprit. If not, then verify the horn has a good path to ground and paint is not preventing that.

If the ground is good, then the horn has a problem internally.

The horns pull a lot of juice, so you need a battery to test with, not a low amp battery charger. I use a bump switch to test stuff like that, then I don't have to work about any arcing/sparks.

Thank you gents.
Howard's comment about reversed wiring got me thinking. The relay is clearly marked with a sharpie "S" for switch on the middle terminal and "B" for battery on the bottom terminal. On the wiring diagram, it is shown as the reverse of that arrangement. Relay is likely not original and could just be different, but would I do damage if I reversed them as a simple test?

When in doubt, go back to basics. Place a clean paint-free part of the horn frame on the positive post of the battery and touch the terminal of the horn with a wire from the negative post. If it doesn't work, the problem is internal. Chances are you did not harm the relay.

would I do damage if I reversed them as a simple test?

Not if it is a standard horn relay. If wires are reversed and voltage is connected where the horn should go on H it is connected to an empty contact and just sitting there. The bat supply has to be connected to B so it can also supply the coil with power. The horn button will then connect the other side of coil to ground at S and relay will close the contacts connecting the voltage to the horns.

If it worked before and you didn't take the wires off/out during rebuild, then it should work and it's not the wiring but horns.
If you took all/some the wires off, then you need to ring out the wires and recheck your connections also.

Got to think "backward" in positive ground systems for current flow... "hot" wires are "neg" and not "hot". Ground is the "plus" side and "hot".

Pleased to report success. Removed horns yesterday and double checked ground connections for paint. Reinstalled and at first they did not work. Then I reversed the "S" and "B" wires. Somebody, sometime, marked the relay incorrectly for battery and switch.
Had to reseal one head bolt, so I hope it doesn't leak.
Many thanks for the help,
Mark

Glad it turned out simple. It is the almost same scenario with B and S reversed as with B and H reversed. Instead of only the empty contact having voltage, the coil got the voltage instead and would operate. Even if it did operate the contact closing applied ground from the horn button so ground was on both sides of the horns.