Headlights Staying On

[grantwils]

my 2001 S200SE is in the auto-sparkies place. HLC relay and Theft Deterrent ECU were changed but this made no difference... Will update soon...

[grantwils]

update... Autospark has sorted it. Not sure how but there's no auto-lights any more.

[Fugu]

update... Autospark has sorted it. Not sure how but there's no auto-lights any more.

Hi Grantwils, i had the same issue with my car, the car leaked prior to my ownership however they got a sparky in who bypassed everything and the result was the loss of the Auto Lights.

I seriously recommend you read my thread to make sure you haven't been left with the same dangerous bypass.

Linky

[grantwils]

update... Autospark has sorted it. Not sure how but there's no auto-lights any more.

Hi Grantwils, i had the same issue with my car, the car leaked prior to my ownership however they got a sparky in who bypassed everything and the result was the loss of the Auto Lights.

I seriously recommend you read my thread to make sure you haven't been left with the same dangerous bypass.

Linky

I think I'll be checking this weekend!

[KentIS300]

Guys it might be a silly question ... my car had the windscreen replaced by one of the previous owners... dont ask me how long ago I have no clue.

Let's say the new windscreen already has a small chip on it.

Does this problem occur to the cars with Xenon lights as well or only the Halogen ones?

[Fugu]

Guys it might be a silly question ... my car had the windscreen replaced by one of the previous owners... dont ask me how long ago I have no clue.

Let's say the new windscreen already has a small chip on it.

Does this problem occur to the cars with Xenon lights as well or only the Halogen ones?

Both types, although the issue is nothing to do with the lights themselves, it is down to water getting in the fusebox due to leaky screen.

A chip wont do any damage, it's down to the window not being fitted right.

[KentIS300]

Nice to know I think ... lol

I don't know how the halogen lights work ... but I have noticed that it is not possible to switch on the Xenon lights without the Key on the on position.

So I was wondering if it was the same for the halogen lights?

[grantwils]

Another update on this...

I had condensation issues and had removed all sorts of interior trim looking for a leak which I never found.

A couple of weeks ago I replaced the cabin filter (less than 5 mins, less then £15, easier than changing a bulb) and condensation issue is gone.

I suspect knackered old cabin filter contributed to or caused this issue which resulted in condensation dripping into electrics in footwells causing headlight issues.

[The Transporter]

If your cabin filter is clogged, thenthe ammount of fresh air from the outside will be greatly reduced and so stale moist air will not be replaced and you will suffer from condensation....

[Jeff Cooper]

Hi All. Goldmine of info on this thread - last Sunday I came home late in torrential rain and found the headlights kept coming on after locking the car up. I've only had the car 2 weeks so didn't know any of the history, but checked the windscreen and its a Pilkington.

I pulled out all the connectors in the fuseboard on the drivers side and gave them all a spray with Contact Cleaner. Then I checked the passenger side and found 3 of the connectors badly corroded and all green and yucky. Gave them a good cleanup, sprayed all round with contact cleaner and with WD40 and the problem has gone.

Then I checked the windscreen - the top passenger side clearly isn't sealed correctly, and the bottom passenger side is also pretty poor. Will be having a go this weekend with the sealant gun. I have no idea when the screen was replaced or who with so I have no real come back - and not sure if the dealer who sold me the car will take any interest. I'll see if a bit of sealant sorts it - given the fact we have rain non stop forecast for the next week will be a good enough test.

I suspect the previous owner sold the car because of this fault - the Battery was pretty low when I bought it but after a good run seemed ok.

I'm relieved it was nothing too major - I guess replacing the antitheft unit may help in some cases, but before any money is spent, a good hour checking all the connections in the fuseboard is well worth it. If I've managed to resolve it then the total cost was £3 for a can of contact cleaner and £6 for a tube of silicone sealant.

Fingers crossed!

[Underdriven]

Hi, I am having a issue on my 01 IS200 where the headlamp relay under the bonnet is buzzing with the car OFF, headlamp switch at any position including auto, the headlamps dim when the relay is buzzing, lights work as normal with car running. I have removed the plugs from my theft ECU and it still buzzes, another thing I did that has me confused is disconnect the plugs in the driver AND passenger footwells one by one and it STILL buzzes. I do have a aftermarket windscreen (starts with Plinkerson or something like that, I know these are the bad ones), I did notice a bit of moisture on one of the white plugs in the driver footwell but as I said, even with it unplugged the relay still buzzes, I have read this entire thread and tried it all including replacing the relay with a know good one so looking for last opinions before I take it to the shop. Appreciate the help.

[Scott W]

Hey Guys, New forum member here. I had all the above issues with my 01 IS200. Lights staying on with key out of ignition, buzzing relay etc. I did have a replacement screen prior to the fault occurring and suspected rain water had got into the fusebox as stated above by several members. However I didn't find any moisture in the fuse boxes.

I work in the motor trade and can get my hands on replacement parts quite easily so I initially I replaced the relay but the new one buzzed also. Next I replaced the light control indicator stalk but sadly the problem remained. Having researched the issue on this forum I noticed lots of people having good results from replacing the anti theft ECU. This worked a treat in my case also and my lights are now fully functional and auto lights are back again. !!! No more inconvenience of pulling the relay out every time to save the Battery. Could not be happier with the car now.

Many thanks to everyone sharing their  experiences and useful advice on this forum.

TLDR : Anti theft ECU was the problem.

Kind regards,

Scott

[Lucazade]

I think I might have found the issue for my car. Typical symptoms, i.e. lights turning on when pulling the keys regardless of the stalk's position, Battery draining overnight, etc. Everything started after having the screen replaced, as usual.

I had the bypass wiring fix done by a car electrician so I lost the automatic lights but was able to go through the MOT. However the problem reappeared roughly a year later. This time I had to pull the relay to avoid draining, but then one day I came home with the rear lights on (feebly) and the horn's relay clicking away. Odd. I thought it could have been the anti-theft unit but that uses a separate horn/siren IIRC.

Anyway, this time I decided to check the windscreens even if there's no trace of condensation in the fuseboxes, inside or outside. I then checked the windscreen defroster (the wiring that stops the wipers from sticking to the windscreen) and although the wires seems ok, the socket was wet and had a little oxidation. I blew the water off, sprayed some WD40, dried it and left it unplugged but wrapped with a rubber glove's (middle) finger to make it waterproof. No problems so far regardless of the torrential rain we've had overnight.

See pics for the area involved, as well as the plug after cleaning it. One thing I noticed is that the cowls' draining slits in that corner don't have a mesh like the others, but I don't know whether it's intentional.

I'll keep you posted.

[Lucazade]

2 hours ago, Lucazade said:

I'll keep you posted.

Fail. Lights just turned back on. It might be a coincidence, but that happened soon after locking the car so the anti-theft might indeed be the cause.

[Lucazade]

BINGO!

That's the "theft warning" ECU, for those wondering what the problem is.

Anybody still struggling with the headlights issue, now you know what to look for.

Still not sure of the connection with having the screen replaced, though ...

[P.Lindblom]

I recently bought an IS300 SportCross and the lady who owned it told me the windscreen had been replaced and since then the alarm goes off whenever it rains. I discovered the front passenger door had a faulty sensor so i mended that, but after a night of heavy rain I woke up to lit headlights and rear lights. When I inserted the key in the ignition the lights went off, but came on again around 30 seconds later. After an hour or so the car had dried up and the lights turned off on their own.

I found and read this thread before diving under the dash to have a look at the Theft warning ECU. It looked perfectly fine on the inside though.

 

The rain started pouring down again and I could see the occasional drop of water falling on top of the right side fuse box. Upon closer inspection I noticed some of the connectors looked pretty corroded and nasty. I decided to remove the fuse box, disassemble it and clean it thoroughly.

 

This pin had almost corroded right off

The main problem is of course the leak around the windscreen, but I bet this clean didn't hurt. I just thought I'd post this to add to the knowledge if anyone else has the same problem in the future.

[marcb]

Just on the offchance there's someone still struggeling with this issue, on my 2001 IS200 I had the 'headlights on' as the only symptom, and the only wet connector was one that went into the foreward side of the theft unit. Drying of which solve the problem.

[scudney]

This(the headlights staying on)seems to be a problem when a windscreens are replaced with non OEM one's 🤔