Horn won’t work in the morning?

Recently installed a grant steering wheel on my 92 c1500. For some strange reason the horn doesn’t work in the morning but will towards midafternoon. The mornings are about 80 degrees at 4:30 am on my way to work. Over 100 degrees by afternoon. So I don’t think it’s a cold issue ?

I'd guess a grounding issue. Try with your headlights on and off and see if it correlates.

vallesfj said:

Recently installed a grant steering wheel on my 92 c1500. For some strange reason the horn doesn’t work in the morning but will towards midafternoon. The mornings are about 80 degrees at 4:30 am on my way to work. Over 100 degrees by afternoon. So I don’t think it’s a cold issue ?

Click to expand...

That's an interesting problem description. I took a copy of the Horn wiring diagram out of the '92 C/K
Factory Service Manual, and took the liberty of coloring the wires in the diagram to match reality.

I also added in some common sense rules for how the circuit operates. I color-coded the rules to
match the part of the electrical circuit they pertain to:


(Page 60 from the '92 FSM)

FWIW, after studying this electrical circuit, I tend to agree with ETA that it may well be a grounding issue. You see, when you depress the
horn button, you are connecting a ground to the horn relay. This ground provides the 12v power from the orange wires a path to
flow through the control coil, which closes the internal contact, and this in turn sends the 12v power down the Dk Green wire to the
horn(s) up front.

So here is a quick & easy common sense check to see if the temperature sensitivity is up front with the horns or not. When the horns
are not operating, pull the horn relay (in the middle of the bottom of the Convenience Center as shown above) and jumper the power
from the bottom connection (12v orange) to the top connection. (Dk Green wire to Horn(s).

If the horns now sound, then we know that the horns are not temperature sensitive, and that the problem must be back from
the horn relay towards the horn button in the Grant steering wheel. If you reinstall the horn relay, now we need to verify
that the relay itself is healthy and a victim of a marginal ground...or is the relay weak and even with a good ground connected
it is still temperature sensitive?

At this point some would advocate to replace the relay with a new one and see what happens. A no-parts troubleshooting
approach would be to jumper a solid ground to Pin G at C206 and see if the existing relay can be operated at will by doing so.

IF this works, then we know that the ground path through the horn button needs to be looked at closely. IF the
existing relay won't work with a solid ground applied to Pin G of C206, then either the relay itself or the connections
in the relay socket are suspect. (And of course all wiring involved too.)

To recap, we need a good, low-resistance ground from the horn button to enable the horn relay, and from there we
need a good path for the 12v power to the horn(s). And Erik is right to suspect anything that might affect the
ability of your horn button's ability to provide a solid ground to the horn relay.

Hope this '92 wiring diagram and the troubleshooting theory helps you track down the root cause of the intermittent
horn operation.

And when you find & fix the problem, please be sure to come back here and describe what it took so that other
GMT400 owners having horn issues in their '95-previous rides can benefit from your experience.

Best of luck --

vallesfj said:

Recently installed a grant steering wheel on my 92 c1500. For some strange reason the horn doesn’t work in the morning but will towards midafternoon. The mornings are about 80 degrees at 4:30 am on my way to work. Over 100 degrees by afternoon. So I don’t think it’s a cold issue ?

Click to expand...

I've heard Grant quality has taken a bit of a dive. Even a couple decades ago when I'd installed several Grant wheels on my trucks, the horn buttons seem kinda cheaply made.

What's funny is I had the exact opposite problem - on one truck, when it got hot outside, the horn would go off all by itself. The gap between the plastic button assembly and the "billet horn button kit" on top of it was too close so just that very minor expansion of materials due to heat would close the gap and blow the horn. My neighbors weren't impressed. A little shaving of the button solved that problem.

An easy test to rule out the button would be simply remove the button from the hub kit before you turn in for the night, then try manually grounding the contact first thing in the morning, when you expect it to not work. If it works.. go for repeatable results and try it several mornings in a row. If it works every time, the horn button is junk. If not, then obviously you have further troubleshooting to do. I'd start simple, check that button.

Richard

Do you have neighbors who may dislike you horn test? Could be the horn try a test light or voltmeter at the wire to it. The horn is grounded through the mount if it turns out to be the horn check that. A 92 should have the spring clip thing to the adapter those can be lose.