I need help from one of you talented DYI'ers (electrical problem related to horn)

[wolfturbo]

So I just scored a nicer 380mm steering wheel and mounted it to my '70S. The problem is now my horn doesn't work. When I push the little spring loaded doo-dad at 5:00 on the wheel hub, I can hear the horn relay click. Likewise, when I have the butterfly shaped horn center on the wheel, I hear the horn relay when I push the horn.

I checked the wire connection at the horn and they were fine. I even connected another horn and it didn't work when the horn was pushed and the relay clicked. Lastly I put a test light on the wires at the horn end and had my daughter push the horn. No light.

So it seems to my ignorant brain that I have a problem somewhere b/w the relay and the horn? Will the relay still click if it is bad?

Lastly, I checked my fuse labels and there doesn't appear to be a fuse for the horn.

Any pointers out there? Suggestions on where to troubleshoot? Thanks to all!


Wolf

[neilk]

I think I had this problem a really long time ago. I think the horn relay is behind the gauges, so pull a relay near the fuse box and swap it out with the horn relay. You should then be able to tell whether the problem is with the relay or the wiring inbetween.

[911pcars]

Rob,
If the relay clicks, the horn fuse (fuse #2 I believe) should be fine. If it doesn't click, check the fuse and make sure it's okay.

If you have a test light or voltmeter, check for source voltage at the horn connector (see below). It should be about 12 volts (or the test light goes ON). If so, the horn should work, especially if it worked before. Consider the test light or voltmeter to be an accessory like the horn. Let us know if you need add'l info on connecting either of the above to the horn circuit.

Some aftermarket horns need to be bolted onto the chassis as that provides the ground circuit back to the battery.

If no source voltage, check the relay and verify source voltage exists at the relay. It could be the relay, but the relay usually works if it clicks. Might be a dirty or loose connection somewhere.

Here is a left and right side view of the horn circuit (taken from wiring diagram SL35 @ http://members.rennlist.org/911pcars/WiringDiag.htm. This may not be your year, but I don't think the horn circuits changed that much.

The L and R horns (#75) use a common brown ground wire and ground connection (#89) as seen in HornCircuit-Left.jpg. The source voltage wire is the dark (black?) wire with the yellow trace. Place the two images side-by-side to connect the wires and you'll observe this source wire going to the horn relay (#49) at terminal 87.

Inasmuch as the relay terminals can't be easily checked with it plugged into the socket, you could indirectly confirm the relay is working by first removing the relay, then use a jumper wire to temporarily connect relay socket terminal 30 or 86 to terminal #87. If the horn is okay and grounded, the horn should sound when this connection is made. This connection bypasses the relay to confirm the horn circuit from this point onward is okay.

Hope this helps,
Sherwood

[Cornpanzer]

Rob,
my car has done the same thing in the past. I can hear the relay click, but no horn. I have found it simply to be a weak connection there at the steering wheel which makes sense due to the recent wheel change. Pull it apart again and check all the connections especially the brass plate on the column. Sometimes mine depends on which way the wheel is turned

[wolfturbo]

Many thanks to all of you talented wrenches. It turned out to be my relay, so it was an easy fix this time. Best regards to all.

Rob Wolford