Samthellam

Hey there, I recently bought a 1990 LS400 and I noticed that the courtesy lights don't turn off even when all of the doors are shut. The indicator light on the instrument panel that lights up whenever a door is open also constantly stays on. I have a feeling that it might be the front driver's side door jam switch but there's just some weirdness with the the interior lighting overall.

If I manually depress the front driver's side door jam switch nothing happens and the lights stay on. However, when the key is inserted in the ignition cylinder in the off position with the door open the car starts chiming and stops when I close the door or manually depress the front driver's switch (lights still stay on including the indicator light)

If the door jam switch is indeed faulty, how do I change it out? I removed the trim and cover that went over the seat belt tensioner (I think that's what it is/called) but it looks like in order to replace the switch I have to remove the entire tensioner. Is my "theory" on how to replace it even remotely correct or am I way off??

The car's the overhead dome light switch doesn't seem to do anything. I switch it to the on position, nothing happens. I move it to the door position, nothing happens. The dome lights themselves work when I use the buttons but the main switch doesn't appear to be functioning.

Last of all, when I'm driving, the courtesy lights will sometimes start to dim until they go out and then will randomly light back up. Every single light does this except the open door indicator light that continues to stay illuminated even when all the other lights have temporarily turned off. Also, the courtesy lights don't go out at all when the car is not running and stationary.

Does anybody know what would be causing all of this to happen? I'm wondering if it's all stemming from one common problem or if it's more likely multiple issues. If anybody knows anything I'd be super appreciative of the help/advice on this one!

Arsenii

Hello,

That's an interesting issue, I've never seen that before.

It honestly sounds to me like an Integration Relay fault. The task of an Integration Relay is to switch off major power consuming systems when there is no one in the car, that's what turns the headlights off after some time and that is what allows windows to roll up and down even when the Ignition is Off before you open the door.

In your case, said relays is also responsible for Interior Lights, Door light on the Instrument Cluster and how they all cooperate with doors. Other thing is the fact that a buzzer is not a part of integration relay circuit, which may explain why it operates normally.

The only way I know of to check the relay would be to take it out and inspect it, which may be a little tricky, since it is a part of an interior fuse box assembly, here is a Parts Diagram for your car. That's all I can think of for now, maybe someone else would also chime in..

Hope this helps and best of luck!

Samthellam

Thanks for the information, I'll definitely check it out! I had read about the integration relay but wasn't completely sure what its purpose was for. However, if it does what you say it's supposed to do then that's definitely something I'll have to look into. Hopefully if the problem is because of the integration relay it'll be a somewhat easy thing to fix like a cooked capacitor or resistor.

Arsenii

Well, those integration relays are not even that expensive, here is one on eBay for example, it is the labor of tearing half of the interior apart to access it that I am concerned about..

Hope this helps and best of luck!