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General Tech Horn Relay Recap for the Record

KVH

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After reading so many posts about the horn relay wiring, including wiring to the corresponding contacts identified on the newer "replacement" relays, I thought I'd try summarizing things. I am hoping this is helpful, at least for the Triumph TR4A, and I'll be sure to edit and correct anything you folks might note as being wrong:

1) W1 and W2, the coil contacts, are numbered 85 and 86, respectively, on the newer relays.
2) C1 and C2 are the switch contacts, and numbered 87 and 30, respectively, on the newer relays;
3) W1, or 85, goes to ground. That's the thinner purple/black wire at the relay;
4) The fused main 12 volt power, the solid purple colored wire, usually with a shielded spade connector, goes to contact 30 (C2)
5) W2 and C2, which are 86 and 30, get jumped, at least on most of the more modern relays. Jumping is made easier by using a female spade connector on post 30 that splits to two male connectors. The end result will be two wires on contact 30, one being the power line from the fused purple wire, and the other being the jumped line going from 30 to contact 86 (which is W-2);
6) That leaves only contact 87. The dual colored wire at the relay, usually purple/yellow, is the switched power, and that wire goes to post 87.

I think that's it. Let me know if corrections are needed. thx
 
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I wanted to say thanks for this info. I have a '66 TR4A. Is this the relay that is mounted in the front right hand side of the engine compartment, very close to the horn itself?

Bob
 
Yes, that's it. Surprisingly, there have been at least three various relays made to replace the original, one being cylindrical, another rectangular but with four contact posts, and, apparently, now just a standard plug type relay, the same you'd see in a car or outboard engine. See pics. This newer version mounts easily using just one of the two sheet metal holes used by the original. Also, maybe worth mentioning, but even with careful placement of the grounding straps on the steering shaft pinch bolts, you can still fail to be grounded if the steering rack itself isn't grounded. My new steering rack was so well coated with paint that I had to scratch off an area to secure a ground. Another recent problem occurred upon discovery that the horn button wasn't making contact with the brass plate inside the steering column housing--but I'd avoid ever chasing that down until all other possible issues were pursued.

PS I'm not using the relay on the left anymore. You can see, however, how I jumped those two contacts, and I've done the same for the one on the right.


Relays.jpg
 
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