Recently, my 1990 Lexus LS400 ran into an electrical problem. I can start the car and drive. However, the dashboard light, radio, and seat adjustment do not work at all. Only the headlight and interior lights work. After a day of driving, the battery becomes drained so I assumed the battery was not getting charged by the alternator. But when I took both the battery and the alternator to my local auto store to be tested, they both tested good.

So my question is what components to check for next? I am guessing the wiring and relays? If so, how to check to see if a relay is in working order or not?

 

Might want to check this first...

http://www.lexls.com/tutorials/lighting/bulbout.html

 

Thx for the info on the trunk wires. I checked and did indeed found two broken wires (One white and one green). However, even after I reconnect the two wires, the problems remain the same. Besides headlight and interior light, all other electrical system do not work. No suspension, no dashboard light, no power window/door lock/moon roof, and no battery recharging. Car still remain startable and drivable.

What other wiring/relay should I be looking into?

 

did you check the fuseboxes inside under the dash and next to the engine for popped fuses...?

 

yes, I have checked all the fuses/fusible links in both areas. They are in working condition.

 

man i got almost the same problem as you but the things that aint working on my car is
my cluster/dash, radio, ac, turn signals, and hazards dont work....

my fuses are still good also
but i think it maybe wiring

 

alright take your positive and your negative on the battery connections and swap them.
Negative on postive and positive on negative, this will fix all your problems and you will come back to thank me.

 

I'd say you have a bad ground somewhere...

 

I just fixed my 98' LS400. It was a cartridge fuse. look real careful because the top of fuse (where you can the copper) was not burned/broken. When I attemped to pull the fuse only the case came up. I could see where the fuse had melted at the bottom. It will be a fuse under the hood and if it was not burned where you can see at the top thru the clear plastic, it should at least be a little cloudy from the smoke generated from when the fuse burned at the bottom. Just fixed mines and have not test drove or anything but I had the EXACT same problem.

 

Thanks very much. It was indeed the 120A Alternator Fusible Link that caused the problem. The top of the fuse was not burned or broken. But the fuse was melted at bottom.

I replaced the fusible link and clean/scrub the connectors. Car now runs great!!! Thank again for the help!!!