My horn is inop and I am pretty sure the switch at the wheel and the horn under the hood is bad.

I have seen on other sites that this was a problem for others but no one ever really tracked down the problem.

I have no juice at the switch under the steering wheel and the horn itself would not work when I tested it.

What is the number one cause for these issue with the horn on the MM?

What is the test procedure to be certain where the issue is. Why would I have no power at the steering wheel? Is there a fusible link under the hood or something I have not found?

Horn works like this. Power goes thru fuse or fusible link to horn, then to wheel horn button switch, then to ground. If you don't have power to horn, trace that wire back to fuse or fusible link. If you have power to one horn wire and not the other, the horn has an internal circuit break. If you have power on both horn wires, and none at the horn switch, you have a broken wire between the horn and switch. I assume you've checked the horn fuse?

I checked the fuses in the fuse panel inside the truck. I was having a hard time locating a fusible link under the hood but I will check and recheck.

I checked for power at the horn itself and my test light would barley light up and then get dimmer and dimmer. There must be a short somewhere partly interfering or an open circuit or something.

My horn didn't work when I bought mine either. I took the horns off and took short pieces of wires to hook the horns directly up to the battery, still nothing. So I went and bought new horns and installed them. Then, when I looked at the switch in the wheel,it was all corroded. After that was cleaned up, it worked like a charm. I would test the horns first and if they do not work, get new horns. Then go from there. Just start narrowing down possible problems.

Same here, horn was inop. the issue wasnt the switch, the wire connections at the horn were corroded through. Fixed that and the horn squeaked. A few days later while perusing a fine automotive section of the junk yard I found a new model Benz E55 that had been rolled and the front end ripped away. Sitting in the middle of the carnage was a new horn waiting for a nice home. I did the most humane thing possible and bolted it on my rig.

It may be unrefined, but it sure sounds fancy.

Just out of curiosity, how well do your wipers park when you turn the switch off? I think the horm and the wiper park circuit share the same power source. I'm using the 87 montero manual, because the only MM manual on Bill's web site is the sorry haynes toilet paper manual and it doesn't mention the horn at all that I can find.

You should have two fusible links, one right at the battery, a bid fat one, and one somewhere else under the hood. Mitsu either likes to put them in a black plastic box beside the battery or on the fender somewhere.

My wipers park perfectly but they do run slowly. I tested the switch at the steering wheel and had no juice but I have fading juice at the horn. The horn is also inop. I tested it and it is bad but it does not explain my fading power that barley lights up the test probe.

I will check by the battery.

On a side note. There is a small black box probably 3" X 3" and it is on the driver side on the fender very close to the firewall. When I remove the top there are 3 jumper wires. What are they?

That's the fusible links. Look for a green one, and disconnect each end and clean up the terminals with contact cleaner. It might not be that color, so clean up all of them.

There are two white ones that look original and one red jumper wire that has obviously been changed because its a bit thicker wire and is a little sloppier looking fit. I fiddled with them once and they looked good.

Its odd to have a jumper wire. That's not much of a fusible link to me. In fact to me its not one at all. All it is, is an extension of the wire. Cut a wire in half and bear the ends and then wire a small piece in between and you do not have a fusible link. To me a fusible link has a fuse.

Are you saying that those wires use to have a fusible link between them and someone just put jumpier wires in there instead?

Like I said the 2 white wires look good and original. They have flat connectors on them. The red one is not so great looking but it is making good contact. I will have to investigate this a bit further and make sure all is connected correctly

Fusible link is a piece of special wire that burns in two with excessive current, like the filament in a fuse. If it's been replaced with commone wire, it's useless.