96' Headlights Randomly Coming On While Vehicle is Off and Locked (1 Viewer)

[Wompom]

Alright Electrical Gurus -

I'm stumped.
For the last year or so i've had my headlights randomly coming on at night, day, whenever, when the vehicle is locked and in park.
This morning I got a call that my headlights were on... the switch was on, but they turn off with the vehicle.
I've also had this happen with the switch OFF.
I replaced the headlight relay a few months ago which seemed to solve the issue at the time.
Additionally i replaced the fuses as they were original and didn't look great, but were not popped.
I'm stumped. I've checked wiring, haven't found any cuts/nicks or something. I can't believe another OEM relay already failed.
I'm running the 8005/06 bulbs trimmed to fit if that makes any difference.
Searched and didn't find anything similar. Anyone have any ideas?

 

[clx16]

Have you checked for a short? Grab the wires and wiggle them around up front. The short to ground right? Is it low beams or brights?

I accidently shorted mine and they came one once.

 

[Wompom]

Have you checked for a short? Grab the wires and wiggle them around up front. The short to ground right? Is it low beams or brights?

I accidently shorted mine and they came one once.

Low beams. I haven't found any shorts anywhere looking through the engine bay. I'll take a deeper dive though, that would make sense. I wonder if having other items on the shared ground could cause it. The weird thing is it'll randomly happen after sitting a few days, not right after turning off the truck or something.
In this case the cruiser has been parked a week, no issues, til this AM they came on.

 

[77mustard40]

Do you have one of the port installed security systems? Just a guess as my lights come on for 30 seconds when I lock or unlock with my key fob which is part of arming the 1990's era security system.

 

[Wompom]

Do you have one of the port installed security systems? Just a guess as my lights come on for 30 seconds when I lock or unlock with my key fob which is part of arming the 1990's era security system.

I do. Wondering if that could be the culprit. It’s worked fine 99% of the time (besides the few times it’s been totally unresponsive for a bit of time). Id really love not losing the fob access.

 

[Rusty Marlin]

I consider myself lucky, The Bean didn't come with a fob, so I never got used to it.
The security system locked me out a couple times while I was working on the truck, luckily the spare key was in the house.
I ripped The Bean's system out by the roots one day after it angered me enough.

 

[gummycarbs]

Bad L1 Light Retainer Relay or D7 diode?

Thread post with wiring diagram.

 

[Wompom]

Bad L1 Light Retainer Relay or D7 diode?

Thread post with wiring diagram.

Interesting - I’ll have to check those. I replaced the relay itself but not the L1 or D7. I’ll see if I can find where they are.

 

[jht3]

@Wompom you ever figure this out?

i swear mine is doing the same thing. i usually turn the switch OFF, but last night let it do its auto thing as a test and meant to double check that all the doors were fully shut and the head/tail lights off (but got distracted by my kid), and came out this morning to dim headlights and a dead battery, so its on a charger now. i don't think the parking lights were on, and i didn't think to check the tails or license plate. i was heading to work so didn't have time to pull out a DMM and test away either.

i swear sometimes the headlights will "wake up" and turn back on if i open/close the drivers door to get something out of it in the driveway. but not repeatable and mostly question my sanity.

my other post on this topic

 

[Wompom]

@Wompom you ever figure this out?

i swear mine is doing the same thing. i usually turn the switch OFF, but last night let it do its auto thing as a test and meant to double check that all the doors were fully shut and the head/tail lights off (but got distracted by my kid), and came out this morning to dim headlights and a dead battery, so its on a charger now. i don't think the parking lights were on, and i didn't think to check the tails or license plate. i was heading to work so didn't have time to pull out a DMM and test away either.

i swear sometimes the headlights will "wake up" and turn back on if i open/close the drivers door to get something out of it in the driveway. but not repeatable and mostly question my sanity.

Not completely. I replaced the headlight relay and it seemed to stop but I noticed it do it once the other day again. Chased a billion things and not sure what it is.

 

[jht3]

dang

i hate to say it, but i don't think changing the headlight relay would change anything. i know my lights switch off proving the relay isn't sticking, but like you, feel they turn back on spontaneously. based on my understanding of the EWD, the ONLY way they can do that is if the headlight relay coil (on pin 4) gets re-energized by the light retainer relay. but i'm not smart enough to figure out how that can happen, or the role of the diode. the tail lights don't have a diode, if anyone can explain that i'd be grateful.

 

[jonheld]

dang

i hate to say it, but i don't think changing the headlight relay would change anything. i know my lights switch off proving the relay isn't sticking, but like you, feel they turn back on spontaneously. based on my understanding of the EWD, the ONLY way they can do that is if the headlight relay coil (on pin 4) gets re-energized by the light retainer relay. but i'm not smart enough to figure out how that can happen, or the role of the diode. the tail lights don't have a diode, if anyone can explain that i'd be grateful.

I agree. The headlight relay is not the issue. The light retainer relay, called "Light Auto Turn Off" in the EWD, runs both the head and tail relays. One would assume that if the low beams are magically coming on, then the tail lamps and side markers are as well. One would need to verify this before proceeding further.

You could also remove the light retaining relay, jump pins 7-3 and 8-2 on the connector, and lights will function normally from the stalk switch.

 

[jht3]

well it did it again overnight. drove the truck to get dinner, and when i got home i left the headlight switch in the full on position. when i opened the drivers door the dash lights extinguished, as did the headlights. exterior and interior were fully dark. i locked the truck w/ the key.

came out this morning to find the low beams on, parking lights on, tail lights on, dash lights on. interior overhead lights NOT on. opening and closing the drivers door kept everything on. switched the headlight switch off manually.

not sure what to test, but its got to be that light retainer relay, right? how and why is it switching the ground back on all by itself? i do still have the TVSS system (not the RS3000) installed, but disabled on the dipswitch as i have no fobs. i don't quite understand if the TVSS has control of the lights?

i did have it on a charger so the battery isnt completely dead. all this cant be good for this new AGM battery

 

[jht3]

now something else odd is happening. with the truck on and headlights on, as soon as i turn the truck off all lights turn off immediately (headlights and dash lights). the auto off timer isn't holding the lights on until the drivers door is opened.

this one has me stumped. guess i need to find another light retainer relay if i want the auto off feature to work, and i do as a safety for when i forget to turn the lights off manually.

 

[jht3]

another update. just went back out to the truck to check the fuses (they are all fine) and the auto off is working as it should. but i don't trust it to not turn back on all by itself so the headlight switch remains OFF

 

[jonheld]

The light retaining relay senses the driver door and is a "one shot". IOW, with the stalk switch in the ON position, and the ignition off, when the drivers door is opened, the lights cut off. In this state, even if the relay senes the door open or close, the lights will remain off.

You either have a faulty light retaining relay or a faulty stalk switch.

I would remove and bypass the light retaining relay as the first diagnostic. Non invasive and simple.

 

[jht3]

yea, i understand that the door switch going to ground signals the relay to switch the lights off. what i can't wrap my head around is the circuitry inside the relay as depicted in the EWD (if it is even accurate). it has been a LONG time since electronics class.

i guess i wonder what the more likely failure is: the light retainer relay or the light control switch/stalk. with the ignition on, all lights work as they should. when the retainer relay isn't even working at all, i lean towards the relay being the problem. and the lights turning themselves back on i do as well, as maybe there is some failure mode that allows the relay to allow current to flow to the light switch again. since it is so intermittent, i'm basically forced to throw parts at this...or bypass the relay as you pointed out. a new relay is ~$140 and a new switch is $100.

the previous owner did install a new headlight dimmer switch, as the high beams were not working properly. that is working properly, and not part of the auto light off circuit.

 

[jonheld]

the previous owner did install a new headlight dimmer switch, as the high beams were not working properly. that is working properly, and not part of the auto light off circuit.

What is a "headlight dimmer switch"? Are you referring to the stalk switch?
EDIT: nevermind. Got you.

 

[jht3]

After turning the ignition off, roughly one minute later I can hear the click of a relay, under the fuse panel. Any idea what relay that is? Might not be light trusted at all

Fwiw, my lights have shut off with the ignition all day today. As another data point, when in this state, i can't turn the parking lights or headlights ON without the ignition on. but flash does work. aren't you supposed to be able to turn the parking lights on with the ignition off? not sure if this helps isolate the issue to either the retainer relay or headlight switch.

 

[jonheld]

I just tested this on my 97 LX450.
Door closed, ignition on. Switch headlights on.
Switch ignition off-lights stay on until door opens.
Once in this state, you must switch headlights off, and THEN the stalk switch controls headlights normally, regardless of door open/closed.