1992 Lexus LS400 212k. Electrical Issue.

I lost horn power almost 2 months ago and then lost headlight power. Mechanic said there is power at the horn/lights and switches but something in between is wrong. HE was able to bypass those items so I have their utility. As I began to suspect there was some underlying electrical/short/failure issue developing. Then while driving a week ago I all the sudden lost power to windows, blinkers, doors locks, HVAC, dashboard gauge lighting and functioning. The battery light came on dim and the car remained running. On the way to the mechanics this day, the power was restored and as soon as I used one of those items, window blinker for example, the system would power off once again. Mechanic held car for a night and said he could repeat the problem and sent the car home with me. I drove it home without the power feature mentioned above. I checked the battery level and they were within normal at rest and within normal when car was running with features working. Again this problem comes and goes this past week but has gotten worse.

The next day I was driving to work and I shut the car off at a light to giggle the ignition switch and the car would not start and just clicked due to dead battery or short. Before I got a jump I checked the battery level and noticed it had fallen below normal (obviously). Then after the jump, I noticed the meter read the volt have increased to running voltage with the numbers strangely rolling backward like a timer. So I drove fast to work and a block way the car stalled again. Jumped it again, got to work and meter again was looking like a timer till the car shuts off. My boss thought "obvious" alternator problem which if I didn't know the recent car history I would agree. Despite that, we pulled the alternator and it came back good on 3 tests. Reinstalled existing alternator, test started with same results, had car towed home.

Things you should know:

1) Previous owner has already made repair to trunk hinge wiring problem, typical. I have looked it over and appears fine.

2) Headlights and horn still work as they have been bypassed as mentioned above.

3) Brake Lights also work.

4) Dome lights work.

5) Center dash console clock (at HVAC location) works.

6) Radio doesn't work and hasn't worked in the year and half I've owed car, or previous owner. Works when sun get really hot in the summer months. I believe its has a bad on/off push switch.

7) I've checks basic fuses and everything checks out ok.

8) As far as relays, ECU and FET I am lost where to start looking.

I've been reading reviews for a week and haven't quite found the solution. I believe this is some simple thing causing my issues and that someone who has worked with these cars should have some ideas where to look for a solution.

Thanks for your time.

Steven Z.

Owner 1992 LS400

 

welcome. moved to the right forum. best of luck.

 

1st check all fusible links, found in the fuse box behind the battery. Make sure no corrosion on battery terminals or on fuses. Same with relay terminals. Simple stuff first.

 

Just to close out this post:

So I discovered i had a pretry bad electrical short wite harness which passes through the drivers side fender and into the under dash compartment. Rewired about 13 fried wires and all my problems went away.

 

Wow ! could have burned the car up. I wonder why that happened? I know old Mercedes have had a wiring issue from inferior wire insulation. This is why any car that sits in my garage has the battery disconnected. I don't know about that harness but there is constant power into the cars at all times, and any number of wires could do that exact same thing and burn your car and house down. Hmmm so tell me how did the fusible links look?

 

Glad you found that. Is there any aftermarket equipment wired into the car that was run through that access opening?

 

And very surprised it didn't mess up something else so it wouldn't run. Very lucky there.

 

that is crazy to see. The real question is 'what caused it' and how to make sure it does not happen again.