Horn / relay diagmostic help

[MikeFike]

I have installed a new horn button and the circuit down to the horn relay seems to be ok, I get a small click in the horn but can not determine if it is the relay or that the horn is bad. Before I pull the grill to get the horn out,,, how do I us a OHM meter to test the relay and the horn to determine if the problem is with the horn or the relay?

[63burban]

If you hear a click, that most likely is the relay, check all the connections and the ground on the horn itself. Pull the horn off and check it on a battery if it works, you should be good.

[tincan1966]

A very simple way to test the horn, is to unplug the connector at the relay, then use a jumper wire from the battery + and touch it to the green wire in the plug. The horn should sound. if it doesn't, then the horn may be bad.
To test the harness from your horn button, connect the clip of a test light to the battery + post, and the test end into the plug for the black wire. when you press the horn button, the test light should light up. if not then the problem is from the horn button out to the relay.
To test the relay, itself. Connect the plug back into the relay, then use a jumper wire from the battery (-) and momentarily touch it to the black wire on the three wire plug. It should click and the horn should sound. it if doesn't and you've already confirmed the horn is good, then replace the relay.

it's easier to do than to type it all out or to read, but this will take about 5 minutes to actually do.

[ray_mcavoy]

I agree ... the test that tincan1966 posted is a quick & easy way to check the horn and relay and determine which one is at fault.

Since the year of the truck in question wasn't specified, I'd just like to point out that the color coding of the black & green horn relay wires are reversed on 60-63 trucks as compared to 64-66. It's a subtle difference but might avoid some confusion if you're dealing with a 60-63.