tahiles

There's a few threads around but they don't really answer my question.

I suspect my Dimmer Switch is bad. Here's why. All the lights on my "center stack" (nav buttons, temp up/down climate toggles, radio, shifter indicators) think it's daytime whether the headlights are on (manual or auto) or the dimmer is in any position.

In the Nav Screen setup is a button for "Day Mode" which the manual states will not show up on the display if the dimmer is turned up all the way....mine's not but the Day Mode option isn't displaying.

I'm thinking the dimmer is bad and the center dash is receiving the signal telling it that the dimmer is turned all the way up when it's not.

Funny thing is, the dimmer works as it should on the main instrument pod. I can't find a wiring diagram to see if the "Day Signal" from the dimmer goes to the entire center stack or if it goes to the Nav which "may" control everything around it? Certainly hope it's not the Nav unit distributing a bad signal ! ! !

Anyone had to replace one of these dimmer - rheostats?

Tom57

Have the exact same problem on '01 (239K miles) for about a year. Mine is intermittent - works fine, sometimes. Unable to diagnose despite extensive research. You're only the 2nd person I've heard who has experienced. Lexus Parts manager has never seen the issue. He's never sold a rheostat / dimmer. There is an MPX network body computer, an ECU, a control circuit and computer for combination meter also potentially suspect in the wiring diagram. Let me know if you learn anything and I'll do same.

tahiles

How did you find out about all the other components in the signal path. Do you have a wiring diagram?

Tom57

D tech at Lexus dealer told parts manager who told me about components in dimmer wiring circuit. (Someone on CL must have a LS electrical wiring manual that would show the dimmer wiring circuit?) Also said to check every fuse first, but since my issue is intermittent, I really don't think it's a fuse. Yours might be a fuse since it's not functioning correctly at all. Check fuse #s 66 (under hood), 2 (driver's kick panel), and 25 (passenger kick panel). (See Owner's Manual for fuse numbers.) My issue occurs after the lights (either just park lights or all lights) have been "on" for awhile.

tahiles

Well...........

There is no fuse #66 under the hood. The three fuse panels have 15, 15 and 11 fuses total and that's how they're numbered in the Owner's Manual.

Fuse # 2 in the Driver's Kick Panel controls Multi Information Display, Audio System, Instrument Panel Light, Turn Signal Lights, Clock, Shift Lock, Sunshade, Power Rear View Mirrors, Fuel Opener System, Adaptive Front Lighting and a few other things. So that one's not a real suspect or I'd have a WHOLE lot more problems.

Passenger Side Kick Panel has 21 fuses, so there is no # 25.......

Don't know where you got this info but it's certainly not good.......

If you have a problem that occurs after the lights have been on for a while that sounds like a component overheating. Using freeze spray on components will help find the problem if that's the case........

marty99

Tom,

Any idea how I remove the rheostat from my 2002 SC430? It's really firm, and hard to reach. I suspect a bad dimmer, but would like to pull it and diagnose before ordering parts.
Thanks,
Marty from Sunny South Florida