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miamilexus

1993 Ls 400 Dome Light Fuse Keeps Blowing

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Dome light fuse in engine compartment keeps shorting out. When the 10 amp fuse blows I lose: dome lights, door locks, steering adjustment, trunk release and the AC has to be reset every time I start the car. Driving me nuts.

1993 LS 400

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Something drawing too much current. Try removing dome light bulbs and replace fuse and see if it blows. Could be a partially blown bulb where filament burnt but reconnected (welded itself) together with a shorter filament length. As a result less resistance and drawing too much current.

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Something drawing too much current. Try removing dome light bulbs and replace fuse and see if it blows. Could be a partially blown bulb where filament burnt but reconnected (welded itself) together with a shorter filament length. As a result less resistance and drawing too much current.

I'll try removing bulbs, but... when I replace the fuse all the functions (dome light, trunk release, steering adjustment, door locks, Auto AC settings) work fine for a day or two, then the fuse blows again and everything is out again. Maddening. :( I was hoping there was a common short that has popped up on other 1993s over the years. So far my search for a cause has eluded me.

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It could be one of the door lock motors too. If the mechnism is stiff the motor will draw more current. If you still see fuse pop with no bulb then you could try the following; sitting in the car rock the door lock switch back and forth many times. If current draw is high it should pop fuse in several cycles. If it does pop then you can narrow down offending motor by disconnecting them one by one (a bit of work as you have to open up door panel).

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No sequence that I can recall before the fuse pops. I'll try the door lock suggestion. Just had both panels off to replace the little plastic clip that holds exterior door handle the the locks. Both sides broke within a week. AND no, not the cause of the problem, fuse popping long before the clips broke. My friendly Toyota/Lexus dealer told me I could not buy the little clips, had to buy the whole door handle assembly. He "generously" offered me both handles at cost-$150 each.

One of the local Lexus repair shops said, "while it is true you can not buy the LS 400 clips separately, you can buy SC 300/400 clips separately and the clips are identical."

Off to start locking doors, then opening/closing the trunk (the only two things we did regularly that might "cause" the overload... never did turn on the dome lights, except to check if the fuse was blown. Thanks for the suggestions. Getting closer to parting the car out. Shame because we have gotten to most of the common aliments on 1993 LS 400 (rebuilt/re-soldered dash lights, two alternators, power steering pump, whole steering system, re-flashed the main computer board twice, redid the whole front of the engine, new radiator, just to name the main fixes).

Starting to think my 2007 IS wheel and tires are worth more than the car, but not giving up yet.

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Now I have gone and done it! Blew the whole mess. :cries: Figuring I would use a 15 amp (instead of the 10) while I sequenced around the car trying to find the "offending" function. I went to start the car to move it to the garage... it would not start. Blew the starter fuse. Got that sorted out, but now as soon as I plug in a fuse in the dome light spot, it blows immediately.

Going to start taking things off-line, starting with the door locks to see if I can locate the problem :censored:

Other than all the dome light functions (which are a lot) the car works great. BTW, no problems in the trunk harness or the interior dome lights.

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..."Figuring I would use a 15 amp (instead of the 10) while I sequenced"...

Well not a good idea doing that as the wire is matched to the fuse of the circuit. This could lead to a fire. Only 5 extra AMPs probably protected you though.

Sounds like a hard short so I agree, just start unplugging the lock motors until the fuse stays put.

Any chance the cigarette lighter is on this circuit? I have seen coins and metallic gum wrappers get down those and create a hard short.

Should be easier to find the problem with a hard short as it won't be intermittent.

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..."Figuring I would use a 15 amp (instead of the 10) while I sequenced"...

Well not a good idea doing that as the wire is matched to the fuse of the circuit. This could lead to a fire. Only 5 extra AMPs probably protected you though.

Sounds like a hard short so I agree, just start unplugging the lock motors until the fuse stays put.

Any chance the cigarette lighter is on this circuit? I have seen coins and metallic gum wrappers get down those and create a hard short.

Should be easier to find the problem with a hard short as it won't be intermittent.

At least you didn't call me an "idiot"... Of course, I have already self-named myself and feel really stupid. :blushing: At least it is a "hard short" might be easier to find and the car didn't burst into flames (a good thing I think).

Too many other projects for the time being. Car just going sit for a while. I hope it is easier, but with all the functions attached to the dome light fuse it may not be that easy.

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..."At least you didn't call me an "idiot"... "...

No idiots here. We all have had things happen we thought better of after the fact. Using a 15A for a 10A branch was a heck of a lot better than putting in a 50A! Then you really could have had fireworks or melted cable harnesses. The risk is if the wire get superheated it melts into other wires and the entire car wiring is damaged (actually destroyed). Then you go from a shorted device (say a lock motor) to replacing the majority of the car's wiring harness. For a car of your age that is probably a complete write off.

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Following up on B's comments, once you've found the offending part, I would check the circuit wiring to ensure the insulation is intact. Do some resistance readings. Make sure there's no connection/activation of components that should be on other circuits. As mentioned, shorted wiring can cause all kinds of failures. Replacing damaged/stressed wiring is the safest course for an older vehicle.

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