[91 Comanche] What does the entire brake/hazard light system look like? (Battery to fuse box, fuse to ignition etc)

[Deadlydudly]

I lost my brake and hazard lights the other day. After checking god damn everything I'm out of ideas. I tested for power at multiple locations and found that I have no power at the Hazard flasher by the pedals or at the Hazard fuse under the hood. To trace what's going wrong I'm trying to find out what the entire system looks like. I'm clueless with circuit diagrams, so can anybody tell me how It works? Battery power goes to what? Then to what? Then what?

[Minuit]

Has the battery been taken out recently? On my 91 there was a small one-wire connector coming from the positive battery cable that came unplugged resulting in exactly those symptoms. I believe the connector itself is red.

[Deadlydudly]

I was one second from replying in defeat when I found the red connector. It runs from the fuse box to a spliced blue wire, which leads to god knows where. I opened the connector and found it green as God's grapes. I'm cleaning the hell out of it as we speak, and am charging my battery on the side. Will reply with the result tomorrow.

[Deadlydudly]

No dice. I think it may have fixed one of my tailights, but the brake lights aren't coming on. I took a 12v wire and directly hooked it up to the brake switch harness (taking the switch off, touching it to the plug it plugs into) and no lights on anything came on (had a spotter watching). I am completely lost at this point. Nothing I do will bring power to the Hazard fuses or light the damn brake lights. It's like the entire system is chooched. Does anyone know the entire system? So I can start from square one and work my way through? AND WHY ARE THERE TWO HAZARD FUSES? WHICH COMES FIRST? The amount of frustration I have right now is phenomenal.

[Green Mesa XJ]

Is this an automatic ? If it's a standard transmission sounds like the fluid got into the fuse box.

 

I'm trying to think about how the power is routed. The fuse box by the batter has several leads going to the battery. Maybe something in there.

Once the power gets to the fuse box I can't think off hand of anything that would stop it going to the hazards or brake lights other than a fuse.

 

 

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[Green Mesa XJ]

Just did some google searching apparently the brakes and hazards do have a wire running to the battery terminal that can corrode away and just drop off.

 

Yours should look something like this. The top lines on mine are for a cheap headlight harness, one big line goes fuse box, one big line goes to the starter. The next oem line has a black plastic clip for fuse or something, I'm assuming this is for the brake lights.

 

 

 

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[Deadlydudly]

Thanks for the reply! I've gone ahead and checked all the harnesses I could find around the battery (yanked it out to make sure). I found this small box on the passenger side firewall unplugged. What is it? Pic can be seen here http://m.imgur.com/mGaNBmA

[Green Mesa XJ]

Kind of looks like a plug to a ABS pump, which you don't have, if you did it was removed, I'll look at our XJ when I get the chance to see if I can see what it does.

 

In the fuse box under the hood, check fuse 13 to see if it gets power. I think that one is where the power for brake and hazard start.

 

Other possibility is bad grounds but since you not getting power I kind of doubt they are the culprit.

 

 

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[Deadlydudly]

I'll be checking for grounds later on. I just found that I have power going into my brake switch through a pink and white wire. Does anyone know what each colour wire represents? Does power go from the brake switch to the fuses, or from the brake switch to the Hazard switch, or directly to the lights, orrr? If I've got juice in the switch, I'm wondering what's stopping it from getting to the brake lights. I'd chalk it up to the ground if it wasn't for the fact that my hazards aren't working too (no blinking on the dash, no flashers, no noises).

[Green Mesa XJ]

Those little hazard relays could be bad. If the turn signals work I'd swap the clicky relays (I forget what they are called) and see if hazards come back.

 

 

I don't know what the colors mean for the brake switch, however it also involves Cruise control, the torque converter lock and unlocking, and the brake lights, not sure which one that wire is for.

 

 

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[Deadlydudly]

Any idea which relays? There are two mysterious ones sitting side by side by my steering column and then a few in a neat row in the fuse box beside my battery.

[Minuit]

If you haven't fixed it by tomorrow morning, I can get you wiring diagrams from the '91 FSM. Won't have access to my books until then.

[Deadlydudly]

That'd be awesome! I was able to push power to the brake/hazard lights by powering the Hazard flasher (by the pedals) and hazard fuse (under hood). So there must be a break in the wiring between the battery and the under hood fuse box (if that's how it works). Seeing a diagram for that area would be fantastic

[Green Mesa XJ]

Sorry I'm probably using the wrong description, cabin fuse box it's the roundish looking things that click at the flashers work. I've had those fail, had a messed up fuse box from the previous owner .

 

But you've found you're not getting power to the dash fuse box so that's the real issue.

 

 

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