The Shop > Electrical

Horn not working - diagnosis?

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86Woodgrain:
My horn does not work. I checked for 12V at the horn connector and it does not get power when the horn button is pressed.

HOWEVER, I checked for continuity at the same connector and it seems to have continuity against the negative and POSITIVE battery terminal. That doesn't make sense to me.

Am I losing my mind? How can the horn wire connector have continuity to power when no one is touching the horn button?

I have read that there is a horn relay so I am going to investigate that next.

Edit: Hmmm and I just realized I can jump 12V directly to the horn to test it.

MIPS:
The horn button goes through the horn relay (because the horn draws several amps and will burn the horn button out) which I *think* lives next to the starter solenoid. Even with the horn unplugged you should hear it click when the button is pressed. It just connects and disconnects always-on battery voltage but I forget if that or horn B+ and the control side are fused.
You can test the horn by putting it directly across the battery.

Illeagle1984:
The horn relay is indeed on the passenger firewall.  It's a three wire thing.  There's a pink wire which should be hot all the time, which supplies power to both sides of the relay, the switch and the load (most relays are 4 wire).  The gray wire goes to the horn button; when it is grounded, the horn relay turns on and supplies power to that black wire.  The horns have a case ground.  So you have a procedure:

- Ground the gray wire, bypassing the button.  If the relay is bad, you can...
- Put power to the black wire.  If the horns still don't sound...
- Put a jumper cable with power directly on the horn terminal.

If it still doesn't sound, the horn is bad, or the ground is bad. :)

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