Weird lighting issue (MJ)

Hey guys, just bought an 87 MJ. The parking lights will not go off. There is a green fuesable link that spreads off into 4 red wires connected to the battery positive, removing that (I assume this is power for the lights) is the only way they go off. My right turn signal indicator stays lit in the dash as well. If I turn the lights on everything works fine, I have park, headlights, and turn signals, turn everything off and just the parking lights and right turn indicator stay on until I disconnect that wire? Thoughts?

The headlight switch is a multi function switch, it is possible for one part of the switch to work and the other part not work. It is possible, as with most all switches for the switch contacts to arch and weld together.

The path is from the fusible link to the headlight switch through a built in circuit breaker to either the parking light position or the headlamp position.

Look at the headlight switch knob, when pushed all the way in, the knob should rest against the the threaded mounting nut. If there is a gap the knob and rod aren't in all the way. The threaded locking nut should be screwed down tight. The knob and rod should be all the way into the headlight switch, it is possible to install the knob and rod partially and not completely. The lock for the knob and rod is under the switch a finger size hole with a locking plunger(button) in there, push the plunger and make sure the knob and rod are pushed all the way flush with the locking nut. Sometimes you have to turn the knob and rod as you are inserting them into the headlight switch, with the locking plunger (button) depressed to get everything seated all the way in. Sometimes it takes a little force to get the knob and rod all the way in, but this is an iffy proposition, if you push too hard you may damage the dash light dimmer part of the headlight switch.

It is also possible to have a partial meltdown of the headlight switch connector, when this happens no telling which wires are going to contact. The headlight harness connector near the air box is also a prime spot for a connector meltdown.

Could be the switch, the switch knob not all the way in, a partially melted connector, or even melted together wiring someplace.

It also behooves you check the size of the parking light fuse. It is not uncommon for that fuse to blow for various reasons. If the fuse is replaced by a higher (than specified) amperage fuse, bad stuff happens, like harness and connector meltdowns.

Most times when that fuse blows it is a problem in the dimmer part of the headlight switch. The dimmer partially shorts out, generates a lot of heat and bad stuff happens. Often the parking light fuse and the instrument light fuse both blow when there are dimmer issues.

Okay.....I unplugged the connector by the air box and the lights stay on(in the back, front lights go out of course), unplugged the headlight switch and the lights stay on, unplugged the turn signal switch and the lights stay on, removed headlight fuse, parking light fuse, and stop lamp fuse, lights still on???? You'd think with all this unplugged they couldn't possibly be on.

Sounds like you have something cross wired or two wires or a connector is melted together someplace.

On the 87 there is no headlight fuse, it is a fusible link, directly from the fusible link near the starter relay to the headlight switch.

Check your PM.

That's my thought....I cut the parking light wire over by the starter relay and still have headlights...the parking lights went out so I figure this wire is hot all the time to the switch so something must be crossed between this wire and the wire to the parking lights themselves? Seem right?

The parking lights and the headlights have the same power source and are switched at the headlight switch. So if you cut a fusible link wire, the parking lights went out and the headlights still worked, you are likely into another sub system and this is the sub system crossing over into your parking lights.

Just on a hunch, do you have a stick shift or an automatic trans? It is pretty common for the clutch cylinder to leak onto the fuse block and partially dissolve the plastic. This could be where the power is getting into your parking light circuit.

Hopefully somebody in the past didn't hook together the wrong wires behind the dash. The radio area is good place to screw this up.

The best approach in my opinion is to look at the book I gave you a link to, find the connectors and segregate the parking light circuit as well as possible (by disconnecting connectors) and go to testing with an ohm/volt meter.

The screws in the drivers side inside door sill are also a good place to start or the screws holding the kick panels on. Even being careful, you can screw a screw through a harness (I've done it).

Maybe pull all the fuses and see what happens, this may help you narrow down the sub system where the parking lights are getting the current from. The "DOME" fuse would be a good bet.

The systematic approach usually works out best, instead of jumping to possible trouble spots.

Actually the parking lights and the headlights have seperate power wires because I cut one of the red wires after the fuse able link and the parking lights went out. The headlights still functioned fine (turned on and off with the switch). The previous owner did install a CD player but why are there light connectors or wires anywhere near that area?

CMNCHE said:

Actually the parking lights and the headlights have seperate power wires because I cut one of the red wires after the fuse able link and the parking lights went out. The headlights still functioned fine (turned on and off with the switch). The previous owner did install a CD player but why are there light connectors or wires anywhere near that area?

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I don't have the schematic for the 87 but it is likely the same as later Renix at least in this regard. There is only one power wire for the headlights and the parking lights. That is a crux of your problem, somewhere somehow you are getting power to the parking light circuit from another fusible link (sub system) you have cut to turn the parking lights off (if I'm understanding you correctly).

It is likely to be a sub system with constant power (it doesn't turn off with the key in the off position). Check and see what else goes off with the parking lights and this may give you a hint where the power is coming from.

Okay! There is a fuse in the dues panel labeled ETR....10 amp...if I pull this fuse the lights go out....the lights seem to work normal without it? Can I leave it out....does anyone know what it is?

ETR is your radio memory and clock power. Somebody likely wired the ETR wire (red and tan) into the radio lighting ( dark blue wire, tied into the park circuit)or the dimmer connection. Or in other words hooked the radio up wrong.

It is also possible your clock is shorted internally, I've seen it before, the symptoms were different though, but still a possibility. Disconnect the clock and see what happens, then disconnect the radio and see what happens. Also check for cut wires in/near the radio well, it happens often.

So evidently the clock/radio must be feeding power to the parking lamps....but wouldn't unhooking the power wire to the parking lamps cause them still to be on if this were the case?

CMNCHE said:

So evidently the clock/radio must be feeding power to the parking lamps....but wouldn't unhooking the power wire to the parking lamps cause them still to be on if this were the case?

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There is no power wire specifically for the parking lights, the headlights and the parking lights have only one power source and that power is switched inside the headlight switch to either the parking lights or the headlights and parking lights. The fusible link you are removing that shuts off only the parking lights is power for the ETR circuit, that is feeding backwards through a shorted or wrong connection into the parking light circuit.

I'm not going to pretend to have figured out every possible wiring failure scenario. Electricity is alot like water, it is going to flow the path of least resistance.

Did you get my PM steering you towards the schematics for your MJ?

I did get the PM but I didn't find any schematics....were they on comanche club? There were some on there that wouldn't open for me? Thank you for that though and all the help really. Someone before me did install a CD player and my clock has never worked. Is it going to cause an issue if I just leave the ETR fuse out?

Found the red and tan wire.....it goes to the clock. With clock and radio unplugged lights still come on if I put the ETR fuse in

Radio has a red wire to battery hot with ignition
Orange wire to constant 12v
Black wire to ground
The rest are speaker wires

CMNCHE said:

Found the red and tan wire.....it goes to the clock. With clock and radio unplugged lights still come on if I put the ETR fuse in

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Do you have any wires plugged into the front of the fuse block, a power wire going someplace or a hot wire part of a trailer wiring harness? I'm not sure but I think the ETR fuse is also for the spot on the fuse block marked BATT, where they usually tapp constant power for a trailer harness.

CMNCHE said:

Radio has a red wire to battery hot with ignition
Orange wire to constant 12v
Black wire to ground
The rest are speaker wires

Click to expand...

CMNCHE said:

Found the red and tan wire.....it goes to the clock. With clock and radio unplugged lights still come on if I put the ETR fuse in

Click to expand...

Do you have any wires plugged into the front of the fuse block, a power wire going someplace or a hot wire part of a trailer wiring harness? I'm not sure but I think the ETR fuse is also for the spot on the fuse block marked BATT, where they usually tapp constant power for a trailer harness.

I may be wrong about the red and tan coming from the ETR fuse (it may be the clock fuse) one reason to find a schematic and use it, memory fails on occasion, the only way to know for sure is to test it (schematics are wrong on occasion). It may be the orange and white wire is hot at all times and comes from the ETR fuse and the tan and red is hot with ignition on, not hot at all times. The dark blue is the parking light circuit. And the orange and black is power form the dimmer circuit. The violet with a stripe is the switched power from the radio fuse.

A straight yellow wire is usually part of the key on power to the ignition control module and alternator power in and is a main motor hot wire with the key in the run position. I'd be careful about hooking anything else up to that circuit.

Red wires are usually wires straight from a fusible link and tend to bypass the fuse block, except as power in wires and not power out wires.

There are 2 wires plugged into the fuse panel....one for constant power to the CD player, one for switched. Unplugged both and the lights still come on. Pulled my fuse panel bulkhead connector apart and it is full of the black tar old dielectric grease...I'm wondering if the problem isn't there?

CMNCHE said:

There are 2 wires plugged into the fuse panel....one for constant power to the CD player, one for switched. Unplugged both and the lights still come on. Pulled my fuse panel bulkhead connector apart and it is full of the black tar old dielectric grease...I'm wondering if the problem isn't there?

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Unlikely to be the cause unless you've had a partial connector meltdown IMO. But probably a good idea to get the gunk out of there anyway, the C 101 connector is full of the same gunk.

Stick your fingers behind the fuse block and see if the wires feel tacky. Clutch cylinder or brake fluid leaking behind the fuse block melts plastic and wire insulation.

how was the radio installed? Adapter plugs or just splices? I'd look at that and check thoroughly, possible that a dash light wire is spliced to something that it shouldn't be?