Tail lights on and dead battery

[kjsmiff]

My daughter drives my 2002 100 series daily and this morning the battery was dead. Funny thing is that the tail lights were illuminated with everything off. I jumped it, then while running had her apply the brakes and nothing changed, the brake lights did not illuminate and the tail lights remained on with all light switches off. Them being on drained the battery but I can’t sort out what the issue is. Any advice would be appreciated.

 

[Godwin]

Check the brake pedal. On earlier models, and I'm assuming the 100 series, there is a small rubber cushion that contacts the brake switch when no pressure is applied to the pedal. When this rubber cushion degrades the brake switch will remain on and brake lights will be on. The cushion is cheap but a pain to install because you have to crawl under the dash to do so. Quick fix might by taping a penny to the brake pedal to shut off the brake lights.

Or I could be wrong since I don't have any experience with 100s .

 

[Mike NXP]

Check your wiring in the rear, may need to drop spare tire...Ill try to find the forum on MUD but I recall seeing few people who had issues with corrosion on either their trailer harness or something similar up there and it was causing brake light issues.

I could be wrong, but you'll just have to diagnose the brake light circuits from one end to another and see whats up...

 

[Mike NXP]

Here is what Godwin is referring to up above, from an 80 series forum..worth investigating

J

Thread 'Brake lights stuck on'

Aug 10, 2019

I went out to take two tires from my car to the shop, when I got there, I noticed all my brake lights are stuck on. Since my car is taking up my garage and it is going to be >100 today, I am a bit limited on how much I am willing to do in direct sunlight to troubleshoot this right now. Any ideas where to start before ripping things apart and looking at wiring?

Figured I'd also post here but also see if anyone know what the heck this thing is from. Coincidentally it showed up in pieces on my driver floorboard, but I don't think it is related.

• jblaze
• Replies: 5
• Forum: 80-Series Tech

• 

 

[Dirt J]

It was the TAIL lights, not the BRAKE lights, correct? If so, were the license plate bulbs on too?

 

[kjsmiff]

It was the TAIL lights, not the BRAKE lights, correct? If so, were the license plate bulbs on too?

I don’t recall if they were or not.

 

[kjsmiff]

Yes, the tail light were on, not the brake lights. The brake lights wouldn’t come on with the brake pressed and the motor running.

 

[kjsmiff]

Trying this again, hoping someone has some experience with the situation. The tail lights and only the tail lights, come on as soon as the positive terminal is connected...no keys, no light switches on, no doors open. Additionally, the brake lights don't work when you do turn the car on. Checked bulbs, fuses, relays and any exposed wires I could find. Disconnected the aftermarket back up camera and display unit which was wired into the panel via the cigarette lighter fuse and the rear a/c fuse and replaced the normal 15A and 30A fuses. I can't fugure this out for the life of me. I have literally had someone watch while I pulled every single fuse and relay individually, just to see them go out and couldn't make them go out. Anybody have any ideas?

 

[89BIGBLUE]

Investigate trailer wiring harness for corrosion/short?
Above spare tire.
Has been responsible for tail light issues and battery drain in a few threads.

 

[Dirt J]

You pulled the 15A tail light fuse and it was still on? If so, something is back feeding that circuit, or a hot wire is chaffed and energizing that circuit.

Is there 12V on the bulb side of the fuse holder when the fuse is pulled?

The relay could also be the culprit. Would be helpful to remove it and manually jumper those leads.

 

[Dirt J]

Do you have the wiring diagram? The tail and brake circuits share the J37 connector and trailer harness connector. Two places to check for shorts.

 

[kjsmiff]

I don't have a reliable wiring diagram, just what google or you tube pops up. I am not 100% positive that I am even looking at the correct relay. Going to drop the spare tire today and keep trying.

 

[2001LC]

I hate aftermarket (AM) wiring. I just had issue, where a 10 year ago installed trailer brake assist. Only now caused, a short. Due to a factory wire that had been cut. Which moved and touched metal. So look close at any AM wiring.

Also look above tail pipe resonator. I've seen where one had a hold in in rear top area. melted a group of wire housing blocks (undercarriage, inner frame RH rear corner. Also look for holes on upper side of muffler.

We've another bunch of wire housing blocks, undercarriage LH rear. Check them out for damaged or aftermarket wiring..

Has windshield be replaced. Is so, look for leaks into cabin. Water intrusion cause all sorts of electrical issues.