1990 Ls400 Radio And Lights Dim And Turn Off

[NYXTOPOULI]

Hi I think I may have a problem but I don’t know what to do. I have a 1990 Lexus LS400

Ok when I first start my car whether it is in the evening or morning I have a problem with my headlights dimming and my radio turning off whenever I press the brakes. Every time I press the brakes the lights dim vastly and my radio keeps resetting itself and turning off and on, I also hear a cracking noise in my speakers whenever the radio resets itself. Also it only happens when I first start the car after it has been parked in the cold, either overnight or more than 6 hours. I don’t know what to do and I think it may be the alternator or there may be short somewhere but I don’t know where to start. My battery runs great and everything and the car starts fine.

thanks Philippe

[VMF]

there is a short somewhere, radio turns off where there is not enuff juice in the system which is proven by dimming lights, check all the brake illumination wiring and cirquitry.

[90LS400Lexus]

I agree. It sounds like a short in the wiring. Could this be linked to the luggage compartment wiring problems? I did not have that woe with my car, but I have read a lot of bizarre electrical problems when that wiring shorts out. Just a thought.....

[RFeldes]

I have noticed, at nite, that when I hit the brakes my lights dim for amoment also. My thought is voltage regulator if there is one. Any Ideas?

[VBdenny]

This could be caused by something a simple as corrosion on your battery terminals or a weak battery. If your battery is getting up there in years, it might just be about done. Put a vOM on the teminals and check output.

[dole2000]

As simple as it might sound, a new battery and terimals can make a world of difference. I had a similiar problem on a car a couple of years ago. Somehow there was a random dead short in the battery itself. I replaced half the wiring on the car before I caught it.

[dogboy]

Dude- I am having the same problem. I just replaced my bat and the terminals are clean just like brand new. (I might add that this problem only started after the new battery)! I have not started tracking down the problem yet. I think that this may be an alternator problem. I know that my power steering rack has been leaking a little, and this has presented a lot of problems for gen 1 LS400 owners. Also I had fixed the control module that lets you know when bulbs are burnt out a couple of years ago. I am going to recheck it to see if it is failing somewhere different on the board. This is the first place that I am going to start. Have you fixed the problem with your car yet?

[dogboy]

I think I have found the problem. I pulled the Lamp Failure module and as soon as I pulled it out the problem went away. I suspected this first because this is the one unit that is tied to multiple systems that has enough power drain to shut down the radio. Also the Lamp Failure would illuminate when this problem would happen. After I pulled the Lamp Failure module I have not been able to duplicate the problem. There are some signs of overheating on the board. I can post some pictures if it will help. Also I am not sure if this was the source of the problem because the symptoms were intermittent and when the Lamp Failure module is out the break lights do not light up so there is note as much drain on the system. The reason I am throwing this out so quick is I have been able to stall the vehicle if I push the break and tax the electrical system (very dangerous at high speeds). Please let me know if this helps!