Another Brake Light Problem

[jeff]

So i recently purchased my 3rd comanche. Its a 1988 pioneer 4.0 auto on the column 4x4. Its got a couple of minor problems of which the one I can't figure out is the brake lights. It seems that they don't come on at all, but when I turn on the running lights the top two bulbs light up in the tails. Also it dosent seem to have reverse lights. The reverse lights I'm guessing is the nss.

[ParadiseMJ]

The reverse lights is either the NSS or the 7.5A fuse under the dash marked TRANS.  Try the fuse first, then you could give just adjusting the NSS a try.  If all this fails, take the NSS out and clean it, re-install and adjust it.

 

The brake lights could also be the fuse marked STOP LPS or more likely the brake light switch.  Both are rather easy to replace.  The 88 brake light switch is much easier and simpler in operation than the later model XJ's.  Should be a 2 wire connector that clips on to the switch.  The switch itself is just one bolt.

[jeff]

I tried to bypass the brake light switch with no avail and replaced the fuse. The plastic shield came off but was otherwise in tact. The light bulbs look fine but I suppose I can pull them out and inspect them further. But I'm confused as to which bulb actually lights up when the brakes are applied. When the running lights are on the top and middle bulbs are lit up but the bottom does not light up which I'm assuming is the reverse lights.

[jeff]

so i tested the switch and it operates like its supposed to and i checked all the fuses

. I also noticed my hazards don't work along with the hi beams. any help will be very appreciated!

[Eagle]

I tried to bypass the brake light switch with no avail and replaced the fuse. The plastic shield came off but was otherwise in tact. The light bulbs look fine but I suppose I can pull them out and inspect them further. But I'm confused as to which bulb actually lights up when the brakes are applied. When the running lights are on the top and middle bulbs are lit up but the bottom does not light up which I'm assuming is the reverse lights.

 

Both lamps in the MJ taillights are dual filament bulbs. They both light up one filament for taillights, and the other filament for brakelights.

 

It's possible the brake light filaments aren't working, but it seems unlikely that all four would have the taillight filaments working and the brake light filaments burning out. Also, if just the brake light filaments were burned out, the hazard flasher should flash the fronts. I think you need to trace the circuit, starting at the brake lights and working forward.

[Pete M]

another thing to look into is there's a connector in the harness just behind the drivers side tire.  corrosion inside stole my brake lights long ago.  could be where your backup lights stop too.

 

is there any evidence of a tow harness spliced in?

[jeff]

alright to add to this today i was leaving class and i start the comanche everythings fine. I turn on the head lights and it stalls out and dies. when i pull the switch all the guages turned off and the headlights wouldnt turn on. so i start checking fuses and nothing. so i start seeing if everything was working. i pull the hazards and try the headlights again and the turn on. so everything seems fine. and the brake lights now work along with the hazards!! also the left hand turn signal light is on on the dash. so my guess is there is a ghost in my wiring somewhere.

 

Pete the harness on the under the bed looks fine and is in good condition. i went through all the bulbs and connectors that i could find and put dielectric grease in them for assurance. it does have a hitch and a trailer harness but i have'nt looked to see if its factory or not. i will do that tomorrow after work.

[Eagle]

For starters, check the ground strap from your engine to the firewall for continuity.