When it rains, my lights turn on

nickbrumme

New member
Hey all-

I read a couple other old threads about this, and even posted in one, but I haven’t found an answer and it doesn’t seem like people are responding to the old threads so I thought I’d start a new one.

I have a standard 1998 SR5 V6 2WD 4Runner. All original sound system and alarm system (I did disable the alarm and remote lock years ago though, so I only use the physical key to unlock. I forget exactly why I did that. I think it was because of something like when I locked the car with the fob and opened it with the physical key the alarm would go off or something like that. Pretty sure that’s unrelated. It was years ago. This current headlights issue is only months old). I do not have the auto off headlights. I have standard headlights.

The headlights work completely fine, everything as you’d expect, but when it rains, they turn on. Even if the key isn’t in the ignition. Clearly some water is getting somewhere and shorting the circuit. When it's raining, keys are not in the ignition and light switch is in the OFF position, the headlights are on. If I turn the PARKING lights on, the headlights turn off (like they should be when the parking lights are on). And of course when I turn the switch to the headlights ON position, the headlights turn back on. But when I move the switch back to the OFF position, the headlights are still on. SOMETIMES going back and forth between on and off like this shuts them off. But only temporarily, and then as it rains more, jiggling the switch like this stops working and the lights are just always on. I've been functioning by taking the fuses out whenever it rains for a couple months now (doesn't rain much in LA). But every so often it starts raining while I'm sleeping and I wake up to a dead battery.

Some more info:
When I turn the car on sometimes after it's been off for awhile (raining or not raining) I hear what sounds like water draining from right where the dash meets the windshield. I'm sitting in my mechanics waiting room while I'm writing this and I told him what I just told you and he says what I’m describing sounds like there's something wrong with the heater core. My cold air AC definitely rarely works, though the heater seems to consistently work... I don't know if this is relevant to the lights. But it seems like a similar area...

One night, it was raining and I had taken the two headlight fuses out like I have learned to do. Went to get dinner and when I came back out to my car, the PARKING lights were intermittently flashing and I THINK I remember when they flashed, the horn also briefly beeped with it? It was probably like every 20 seconds or something it would just barely flash & beep for half a second. This only happened that one night (that I saw). Usually (to my knowledge) when I pull the headlight fuses out and it's raining, everything stays off. To my memory it wasn't raining particularly heavy that night either...maybe just more consistently?

Pretty sure that's all the info I have related to that issue. I first noticed it happening probably 6 months ago. But it hardly rains in LA so I've lived with it. Maybe it was happening before without me knowing. It took me a second to put it together that it was happening while it was raining. But it’s definitely only when it rains.

Any ideas about what exactly is happening and how to fix it?
 
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Yes, the Durk is the man for this stuff.

I'll relate an experience I had once.

When camping in Zion NP during a freak cold spell/snow occurance, we got a LOT of condensation in the runner over the week we camped there. We had a small electric heater so we were comfortable but a lot of wet built up on the windshield, to the point it ran down in drops and went somewhere. Where it went was at least partly in the fuse box/control module under the drivers dash.

After a couple of days parked, not moving I noticed the airbag light was dimly lit one night. Not even keys in the ignition. I have a built in volt meter that measures from the key switched accy. circuit, and it was on and reading 3 or 4 volts, again with the key out!

I posted on the forum here and no one really had much insight. After a day of this I had a thought about the water. I put the heater on the drivers floor pointing toward the fuse block and dried things out. And the problem went away. We have since been careful to avoid such extreme amounts of condensation by installing vent visors and leaving the windows open more at night. That was a few years back and has never happened again.

So, to get to the point, any chance you have a leak allowing water onto one or the other of the fuse/relay blocks?
 
Thanks guys! I'll send him a PM and post back what I learn.

any chance you have a leak allowing water onto one or the other of the fuse/relay blocks?

I think that sounds like a probable hypothesis—I'm not too sure how I'd check or fix that though...any ideas?

Thanks again!
 
no response from thedurk yet, so I'm bumping this thread. Anybody else have ideas? It seems like other people have had this problem too
 
no response from thedurk yet, so I'm bumping this thread. Anybody else have ideas? It seems like other people have had this problem too

El Durko is a busy man, and he lives where it snows which means he is probably digging out of winter. Never can tell! So here is my quick read on the situation.

I'm going to assume you don't have DRL's. And since pulling the fuses mitigates your problem, I'll also assume the HL relay is powering the lamps all the time.
In order for the HL relay to provide power to the lamps, it needs to be grounded by the logic circuit in the combination meter. But all the HL circuits flow through the Body ECU, which is the fuse panel next to your left knee. The Body ECU is your most likely failure here because in addition to power, the lamps need ground, which is provided by the switch, highly doubtful both the comb meter and the switch are failing simultaneously. So I'm looking at the Body ECU.

Let's start by having you confirm the HL relay circuits show this.

Pin 4 and 2 have power all the time, this is normal.
Pin 3 has ground all the time(not normal)
And Pin 1 should have nothing with the power removed, or it will be grounded through the lamps. You could apply power here and see if the lights turn on.

I'll follow up with you later to see if you checked anything!
[MENTION=10169]TheDurk[/MENTION] :cheer2:
 
Thanks [MENTION=102597]IBallEngineer[/MENTION] !!! I will check those things with my multimeter when I get home. Just to confirm–pins 1-4 you're referring to are the sockets where the fuses that I've been pulling live in, correct? Like I pop my hood to get to them, they're NOT next to my left knee, correct?

Assuming you are talking about the two I've been pulling, pins 1-2 are from the top HL fuse and 3-4 are from the bottom HL fuse, L-R respectively, correct? Forgive my ignorance, I'm suuuper DIY and new with this stuff.

Thanks again for your attention!!!
 
Thanks [MENTION=102597]IBallEngineer[/MENTION] !!! I will check those things with my multimeter when I get home. Just to confirm–pins 1-4 you're referring to are the sockets where the fuses that I've been pulling live in, correct? Like I pop my hood to get to them, they're NOT next to my left knee, correct?

Assuming you are talking about the two I've been pulling, pins 1-2 are from the top HL fuse and 3-4 are from the bottom HL fuse, L-R respectively, correct? Forgive my ignorance, I'm suuuper DIY and new with this stuff.

Thanks again for your attention!!!

You are correct they are in the engine bay fuse block, but not the fuses, the 4 pins are used for the Headlamp Relay. This is in the middle of the fuse block, close to the fog 15A fuse.

Ignorance is not a bad thing. It simply means you lack some knowledge, which you are working on fixing right now!

:couch2:
 
El Durko is a busy man, and he lives where it snows which means he is probably digging out of winter. Never can tell! So here is my quick read on the situation.

I'm going to assume you don't have DRL's. And since pulling the fuses mitigates your problem, I'll also assume the HL relay is powering the lamps all the time.
In order for the HL relay to provide power to the lamps, it needs to be grounded by the logic circuit in the combination meter. But all the HL circuits flow through the Body ECU, which is the fuse panel next to your left knee. The Body ECU is your most likely failure here because in addition to power, the lamps need ground, which is provided by the switch, highly doubtful both the comb meter and the switch are failing simultaneously. So I'm looking at the Body ECU.

Let's start by having you confirm the HL relay circuits show this.

Pin 4 and 2 have power all the time, this is normal.
Pin 3 has ground all the time(not normal)
And Pin 1 should have nothing with the power removed, or it will be grounded through the lamps. You could apply power here and see if the lights turn on.

I'll follow up with you later to see if you checked anything!

[MENTION=10169]TheDurk[/MENTION] :cheer2:

El Durko fled all that snow over a month ago for sunny Brazil, where I am working on my tan and playing with my new grandbaby. Sorry, I have not been able to get on the forum much. Internet here is a rare privilege, and when I do, I don't have access to my EWD library. I'll be back on Friday.

For the record, I do not do PMs. I tried it, and I hate it. If you can't solve it in one post, then every time you have to go back and open the previous PMs to see what has been done. In a thread, I can just scroll.

So NO PMs, please, unless to alert me to a thread. That's fine.
 

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