DOME Fuse Blows as Soon as New Fuse is Put

[Aesyrin]

Hi guys,

Just recently got a 1992 LS400. Everything works mechanically, but I've been having some electrical gremlins.

This is a list of things that don't work: 

• All interior lights
• Trunk release
• Speedometer
• Radio
• Power door locks (key and door panel button)

The ONLY fuse (both in the engine bay and driver footwell) that's blown/bad is the DOME fuse, everything else is intact. The only issue I was trying to fix when I started this was the interior lighting so I could get in at night and be able to see. I checked every interior bulb I could find, and there was not a single blown bulb. I tried disconnecting everything the factory manual said was linked to the DOME fuse (anti-theft ECU, door locks, radio antenna, wireless door lock ECU, etc.) but nothing works. I even switched out the fuse box with another I had from a parts car I took the engine out of, and it does the same thing there. The annoying part is that with the car off, key out, and doors closed, the instant the fuse touches the terminals there are visible sparks and the fuse blows. Even did it with a 15amp that I tried. The only thing I can think of is somewhere in the harness it's touching another wire with a massive amount of constant current, but I wouldn't even know where to begin to look for broken wire. Nowhere in any of the areas I disconnected or at the fuse box did I see any signs of worn, frayed, or brittle wire insulation. Anyone have any suggestions where I should look next or what all the non-functioning items have in common?

Thanks in advance,

- Frederick

[RX400h]

If there is an Auto-Electric shop in your town, I'd recommend taking your car there, as that type of shop specializes in electrical shorts, drains, etc.

[CliffLS400]

I have a 97 LS400 I bought for $400 due to blown air suspension (replaced with springs) and broken front passenger window, among other things. My most recent issues are almost identical to the post above, but began with this:

Inoperable: Dome light, interior floor and overhead lighting, key fob, door locks (unless key in ignition and turned to on). steering column, adjustable mirrors

Due to these issues, I purchased a new multiplex computer for the driver's side door). After installation, I reconnected the negative battery cable, started the ignition, and realized the lights on the driver's side door lock and window control were off. I then discovered the following were no longer working, in addition to the above:

Inoperable: Sunroof, windows, door locks (even with key in ignition turned to on or full crank), trunk switch

I suspected a fuse and determined the #21 "DOOR" fuse in the interior fuse box was blown. I attempted to replace it three times and every time, the fuse immediately blew.

In the engine fuse box, I determined no current was passing through the following fuses (with the engine running):

- "DOME-RR" 7.5 amp fuse

- "MIR-HTR" 10 amp fuse          - "SEC HORN" 7.5 amp fuse

- "ECU-B" 15 amp fuse             - "DOME-FR" 7.5 amp fuse

I really would appreciate some guidance. From the posts I have read it could be the BODY ECU (if this is different than the Engine ECU I would like to know, as I had the engine ECU examined for capacitor issues and was told it is in perfect working order). It would be the door actuators, the locking mechanisms, sensors on the locks, etc..

Please advise, if possible.