Horn Question

paynzer · Post by **paynzer** » Thu Jul 22, 2010 12:04 am

I have a horn replacement switch that I ordered awhile back from I don't even remember who... anyway, it is like those in the m151, it has a button assembly that fits perfectly into the top of the steering wheel and a single wire that runs down the center of the column (where the original push rod would be) and terminates with a packard connector.

How does this wire tie in with wire 25 to make the horn work?

Anybody use this as a substitute for all the expensive original stuff?

Thanks for your help, paynzer.

Post by **wesk** » Thu Jul 22, 2010 1:24 am

Try the M151 tech board on the G503 site. Perhaps they can show some photos of how the wire is routed on the M151. Is the wire long enough to exit the bottom hole in the gear box where the original horn switch mounted?

paynzer · Post by **paynzer** » Thu Jul 22, 2010 7:31 am

Yes, the wire sticks out about 8 inches and the end of it has the male terminal like a military one so I stuck a packard connector on it. It looks great and fits great. I just don't know how to wire it !!! Seems like a simple thing, but I always thought a switch needed 2 wires going to it and this only has 1, but so does the m151.

paynzer · Post by **paynzer** » Thu Jul 22, 2010 7:55 am

Found the info on the g503 site. Hope it's ok to copy and paste it like this...see if this makes sense:

"The horn wiring is "live"..... there is a live feed to one side the horn and the wire FROM the other side of the horn eventually goes up the steering column. When you press the horn button, all you are doing is earthing the live feed where the horn button touches the column. As the power flows to earth, the horn is activated. Many people think that when the horn button is pressed, it "sends" power down the wire and "to" the horn. Not so. That is a system that is found on some autos these days, but the mutt isn't one of them. "

Sounds to me like the ground wire from the m38 horn would connect to the wire coming out of my steering column and the switch actually grounds the horn when it is pressed. Wire 25 goes to the terminal that feeds the horn. This would make a circuit of 2 wires interrupted by a switch.

Post by **wesk** » Thu Jul 22, 2010 9:31 am

First of all make sure the horn button will actually function on the M38 steering wheel.

The M38 system did not require any good grounding between the steering column / steering wheel and the body. Your new M151 switch must have a good ground path through the steering column to the body.

Using an ohm meter check for an open between the end of your wire and the steering column. If it is open that is good. If it is closed (shows continuity) that means the M151 switch is already grounded out and if connected to the horn will blow it all the time.

Then press the button. If it works the ohm meter will indicate continuity. If no continuity the M151 button is not grounding out to the column.

If you determine the new button does function correctly then the next step is select the #25 wire that is hot all the time. Connect it to the horn. Then connect the horn's ground wire to your new wire.