No Horn Cruise Or Hazards

[jeramya]

I have an 89 Comanche 4.0 auto the horn hazards and cruise have not worked since I have owned it. I checked all the fuses under the dash, all are good. I'm assuming there all 3 connected in some way. And ideas would be appreciated.

[gogmorgo]

What makes you think they're related? The three are connected by the ignition switch, meaning you'd also have lost things like gauges, radio, clock, wipers, heater fan, etc. The cruise control and hazards do kinda meet again at the brake pedal switch, but that might be pushing things too far...

 

Horns are pretty common issues... most people don't use them enough to notice immediately that something is wrong, and even then, most don't really care that it doesn't work.

You may have either one or two horns on your MJ equipped from the factory. If you look straight up from underneath, kinda below/behind your headlight you should be able to see the horn(s. If you've got two it'll be one on each side, but if it's only one, it could be on either side). There's a rubbery deal (think it's part of the inner fender lining? not sure) that you might have to pull out of the way. The horns look like snail shells. Pull the connector off, make sure it isn't corroded, and stick a test light in it. If there's power to it when the horn button is pressed, likely the horn is bad. If not, you've got more work. There could also be an issue with the grounding point of the horn (the mounting bolt). Horns can be completely destroyed if a small amount of moisture gets in. Dust, dirt, mud, spiders, etc. Fortunately, they all work the same so it can be replaced with any random horn off any random car at any random junkyard, although some will require you running a separate ground wire.

If you've got no power to the horn and you can't hear a relay click from under the dash when you push the horn button, chances are pretty good the relay's bad. Good, but not guaranteed. There could also be an issue with the wiring to the relay as well. You can check that with a test light and/or voltmeter in the relay socket. You should have constant power to one of the three terminals, and continuity to ground on one of the other two sockets when you push the horn button. The other one is the 12V feed to the horn, and is only powered when the button is pressed with a relay in place.

 

Hazard lights. Most likely cause is the flasher unit failing. To test it, swap it with the turn signal flasher, and see if the hazards (and the turn signals) work. The flasher units are in the fuse panel. They're the cylindres in the top left (turn signals) and bottom right (hazards) corners.

 

I don't know much about cruise control. I'd suspect a vacuum leak, but I really don't know. A few members have had trouble with the brake pedal switch that disengages it, but I don't know enough to really comment on this.

[kroyusa]

A broken clockspring in the steering wheel can shut down the horn and the cruise, not sure if it affects the hazards.

[sloride]

The wire at the brake switch on my MJ separated more than once causing loss of cruise. I check that first if I were you. My horn works but it has to be massaged rather vigorously a certain way. I think that's a contact issue though I've yet to address. If your hazards don't work, do your brake lights? I'm assuming they're related, but I've not had that problem on a comanche so I don't know for sure.

[cruiser54]

Hazards are not powered through the ignition switch.

 

Comanches never had clocksprings.

[jeramya]

Yes my brake lights work. I also have vacuum at the thing under the hood that controls the throttle. What does the brake switch connection look like?

[cruiser54]

Look up at the top of the brake pedal. There are 2 switches. The metal one is for brake lights. The white plastic one is for unlocking the torque converter and dumping the vacuum to the cruise control servo.