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Headlights Staying On


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Like it say's, since New Years Eve my headlights have started the staying on, on there own whe the keys are out.....

I have read a couple of other topics but have not cured the problem fully.....I spent a couple of day's finding the problem to be moisture in one of the blocks in the drivers side fuse box....the block that is linked to the headlamps.....only by pure chance did I notice that it had some sort of moisture on the block and a slight green colour on the block indicating corrosion/moisture.....all the other blocks seem to be fine only this one, I reallt need to know where is this moisture coming from.... Before you ask the windscreen has never been replaced..

I have cured the problem for now with a hair dryer and dried the block out and it worked for 2days and back they come on....so dried out again and no flat Battery in the morning for work...

I have had my head under the dash looking for water marks of some sort but unable to find any and all the other wires are dry too..

Can I use wd40 to prevent any water getting in or does the block need to be completly dry to prevent the headlamps coming on....don't want to try it if it does not work as then you got to get the WD out of the block....

was thinking vasaline but not sure if the water is running down the wire or actually coming out of the fuse box....

My head hurts with this one and fed up looking every 10-20mins to see if they have come back on....

Help please guys....I know some of you have had this problem and need to know how you cured it... :shifty:

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windscreen normally needs to come out and be resealed - new screen in other words!

but I can't see any water marks or anything from that area...and what puzzles me more is that the only block to have any moisture on it is the one used to control the headlights..

could it be all this snow which is settling on the car around the windscreen????

If I need a screen well it looks like I will have to crack it then so to speak..

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its possible that the pipe for your sunroof is leaking aswell, but the problem usually occures after the replacement of the windscreen.

try sealing the plastic cowl into the recess, that the fusebox rear relays are sitting in

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its possible that the pipe for your sunroof is leaking aswell, but the problem usually occures after the replacement of the windscreen.

try sealing the plastic cowl into the recess, that the fusebox rear relays are sitting in

Not had a new windscreen fitted Mat...

Will have a look around the fuse box and see what I can do but it is strange that I can only see moisture on the plug that controls the headlamps..

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ok, give the contact a good clean then use a water blocker- u get the stuff in car shops to seal ignition systems, spray that around and see what happens.

also check as mat said that the sunroof is draining pour a bit of water in the drain channel of the sunroof( open roof for this) and see that water appears near the rear wheels after a minute or so

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Will have to have a look tomorrow guy's and see what happens, the car is now covered in snow again and the lights are still off after 2hrs of checking...

This is the first fault I have had with the car and owned it for 6yrs....not bad but annoying..

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You could leave a bit of kitchen towel or similar wrapped around the cable for the headlight relay. That way any water that does get down the harness will get soaked up.

Dunno if it also makes it a fire risk, but mines been fine since.

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well had a play in the fuse box area and dried the plug out again and cleaned a couple of the pins as they had a bit of corrosion on them and also tightened up the conections in the plug by bending them slightly and sprayed a bit of wd40 in there and they are off at the moment..

the moisture was so little you would not notice it if you were not looking for moisture if you know what I mean but that bit plays havoc in there....

So I wait patiently now to see if they come back on and then will try more things like wrapping a bit of cloth around the wire...

all your help is appreciated lads....

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I too, suddenly have this same problem - IS200SE (2002) and have posted on the other (very long) thread on this topic. The driver's footwell relay board seems perfectly dry, but in light of this thread, I must check it again tonight and try using the hair dryer. It has been exceptionally cold here in Scotland. Did you also have the other problems at the same time, such as petrol gauge reading below zero and flashing, no MPG or temperature readings, etc?

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keeping the lights on Auto, can reduce the life of the lighting relay aswell causing it to stick on

I've switched the auto lights off for now and 3day's now no problems...fingers crossed....but the car has a good 4inch of snow on it after I parked it and with the car still warm, it will melt and find it's way to the plugg that is of concern.... well it has been 2hrs and still off so looking good up to now....

Still annoying that a bit of moisture can cause a huge problem...

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keeping the lights on Auto, can reduce the life of the lighting relay aswell causing it to stick on

I've switched the auto lights off for now and 3day's now no problems...fingers crossed....but the car has a good 4inch of snow on it after I parked it and with the car still warm, it will melt and find it's way to the plugg that is of concern.... well it has been 2hrs and still off so looking good up to now....

Still annoying that a bit of moisture can cause a huge problem...

Had quite a bit of rain here in the south before the snow and i was suffering with excessive moisture inside the car on the windows i discovered in the passenger footwell was soaking wet i found twigs n muck in the sunroof gullys(cant think of the technical name)cleaned that out and seems better

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Further to my earlier post on my very similar problem, I can give a brief update. Although the wires and plugs in the driver's footwell relay board looked dry, I removed the lower plugs and gave everything a good heat for a while with a hairdryer. On re-connecting the Battery the problems seemed to be gone - the gauges, etc. started working properly and the headlight relay could be put back in without the headlight coming on. This situation lasted around 10 minutes before the outside temperature indicated 'E' again and the other problems returned and the headlamps came on by themselves again. It was too cold and dark to do much more last night. It looks as if the slightest amount of moisture can cause the problems.

I am sure the problem is somehow related to the extremely cold weather, but what can be done in the meantime? There is definitely nothing wrong with the headlamp relay itself, I thoroughly tested this independently. However it is obviously getting a 'ground' from one of the other alternative sources other than the normal stalk switch. The wiring diagrams are not the easiest to follow but possible alternative sources seem to be the rear fog-light switch, auto light system, or anti-theft ECU. It would be nice to try to isolate which one of these sources is the problem. But how is the non-function of several of the gauges, rear screen heater, etc. related to this? What is the common factor??? I can try drying out again with the hairdryer and spraying with anti-moisture contact cleaner/protector......... Also, have not looked at the board in the passenger's footwell yet. Anyone got any further thoughts....?

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Last week my the front lights on my car started coming on after 10 mins and have been pulling the relay out ever since. Local Lexus garage say they seen this numerous times and they're sure water coming down the cables into the electrics (ECU I assume) following a replacement windscreen. Windscreen was replaced years ago and driver side looks dry but they're convinced!

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:shifty: well since my problem started and finding it to be moisture causing the problem I dried the plug that was causing the headlamps to come on and sprayed WD40 onto the plug and the problem seems to be cured but I still keep looking out of the window to check the lights are still off...

So for you guys that are having the same problem, dry the plugs and spray some Wd40 onto them...

I will let you know if the problem re-occurs...

Thanks for your help guys :whistling:

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Thanks for this encourageing information. I was a bit reluctant to spray the plugs with anything but may now have to try this. I would still like to find the source of the problem. Did you manage to identify one connector in particular - different ones were highlighted in the other (very long) thread? Also, did you experience the other symptoms of gauges reading zero, e.g. petrol gauge, etc?

It appears that the headlamp relay coil is getting a 'ground' from one of the other possible sources, thus completeing the circuit, and energising the relay. It is not very easy to see what all the other possible sources are from the wiring diagrams I have. I would ideally like to isolate the sources, one by one, to find out which one was causing the problems. Also, the relay board in the driver's footwell has an add-on extension module to its left hand side, with connectors attached, and this is not featured in the wiring/layout diagrams I have. It thus looks very difficult to do any logical faultfinding.

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