I recently noticed that my horn is not working. It used to work.

Today I dug in did some diagnostics. I used the 95 service manual found on the forum, page 8G-2.

Test results:

I have two horn relays, both of them behave as they should as described in the manual. Continuity between terminals 1 and 3, no continuity between terminals 2 and 3. With terminal 1 grounded to a battery, terminal 3 connected to battery positive, the relay clicks and there is battery voltage at terminal 2.

The relay socket has battery voltage at cavity 3, and no ground continuity at cavity 1. Activating the horn switch provides ground at cavity 1.

I disconnected the horn wire and applied 12v directly and the horn sounded.

I jumped relay cavities 2 and 3 and the horn sounded.

I reinserted the relay and checked for ground at the steering column horn switch wire, there was continuity and my multimeter indicated it also detected voltage so I switched modes and sure enough there is battery voltage on the wire.

I have two horn relays and both of them are allowing 12v positive on the steering column wire that should be for ground. I took the relays apart and I noticed a diode inside of them. If I tested these diodes correctly, they appear to be passing current both directions.
I didn't know why there would be a diode in a relay so I researched it and apparently it is called a flyback diode and is to provide a path for coil current to flow when it is de-energized.
The diodes are between pins 1 and 3, with the anode on pin 1 and the cathode on pin 2. A failed diode would allow current to flow in reverse and energize the horn switch wire.
Since I have two relays, I removed the diode from one and reinstalled that relay. I still have 12v at the horn switch wire and a non functional horn.

Has anyone else encountered an issue like this before? Do I have two bad relays or is something else going on?

 

It would be impossible to have 12v on the ground wire if it were grounded....if you're checking voltage with it lifted and in the air that's normal...you would have a floating voltage there because you're reading the 12v through the coil windings of the relay...the windings would only provide a small voltage drop.

If the diodes are passing current both directions that's definitely bad...but that would be a dead short and cause the fuse protecting that voltage supply to pop. The flyback diode is to allow the magnetic field of the coil to collapse and not inject voltage back to the supply.

From your tests the relay sounds fine....if you ground pin 1 and apply voltage to 3 and it clicks and you have voltage on 2 that's correct. With the relay in the socket are you able to hear it click? How are you measuring 12v at pin 3 with it in the socket?

 

Thank you for your reply.
The 12v is with the steering wheel cover/horn switch removed.
If I understand correctly, the 12v at the wire is normal.

The relay does not click when in the socket. I tested the relay on the bench with a battery.

 

Make a couple of test leads from some scrap wire....two pieces a foot long. Strip both ends. With the relay removed put one wire in the 3 socket and one wire in the 1 socket.

test the 3 wire to a ground bolt with meter...usually there's one near the left kick panel. With meter on dc volts red lead on 3 and black lead on ground bolt you should have 12v. If not your supply voltage is missing or the socket is bad. Next put your meter leads on the 1 wire and ground bolt. Put meter on ohms or continuity. You should have open or inifinite. Press horn and you should see it change to 0 or near 0. If not you have a bad switch or bad ground or bad socket. If you can get access to the switch test both sides of the switch to ground. With one meter lead on ground bolt and other lead on eithet side of switch. One side should always shoe continuity to ground...the other side should go to ground when you press the horn.