paradox

Hey guys.... this just happened today. Normally, when I turn on my headlights, the dash display would dim. When the headlights are turned off, the tach, speedo display etc would brighten again. Been like that since I purchased the car, and I always thought that was copacetic. So, I'm going down the highway, it starts raining like crazy, and I turn on the headlights. Dash display dims like it usually does, then a coupla minutes later, it goes black for about 2 seconds. It comes back on, but now it's bright, like when the exterior lights aren't turned on. Hmmm, I says to myself, what's going on here? Then.... everytime I went under an overpass where there was significantly less light, the display gets dim again. Soon as I'm out, it gets bright. This only with the exterior lights on. No problems with it off.
So.... where to begin troubleshooting? Maybe a short? How do I isolate? Anyone ever heard of anything like this before? Any help would be mucho appreciated!!!

media2lexus

When I first purchased my 1998 LS400, I observed exactly the same thing. This is normal for this car. The light sensing device (located on the left side of the dash, right beneath the windshield) is activated when the lights are on and when you rheostat for your display is not turned all the way to the right (and clicked in place). What happens is that with your headlights on, it is trying to adjust your display brightness.

If you have your display turned down almost all the way off (but not completely off), when it senses that it is darker out (i.e. going under an overpass) the display will go off altogether.

I had to take my car to the dealer at least twice before this was explained to me.

I hope this helps.

paradox

Hi media2lexus.... thanks so much for your reply. I really thought something funky was going on with the old girl. I had called Hennessey and asked them, and the service tech said he never heard anything like that before, and to bring it in. Confidence inspiring, isn't it? Anyways, I REALLY appreciate your response. Thanks again!!