THXDOC

Ok- I have a transient short I would like help locating- I can start my car but sometimes the park interlock stays locked in park, the dash lights and gauges are black, no keyless or door locks or power steering. I can even drive it like this if I over ride the park interlock although it's like a ghost ship to drive with no lights or instruments. (I realize there is a problem with instrument lights in these cars, but this is above and beyond that problem).

Then all of the sudden everything pops on and all is right for awhile. These shorts correspond loosely with fuse #9 circuit, but that fuse isn't blown. I'm thinking loose block connector or ground wire somewhere? 93 LS400 btw.

deanshark

Search for broken wire on trunk hinge.

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

THXDOC

Two new clues- this "blackout" condition can be triggered by a large amp draw- such as turning on the rear defrost- and temporarily "cured" by flooring the accelerator while at highway speed- which would produce an amp surge from the alternator, right? I'm going to clean up battery connections and ground wires.

timmy0tool

iTrader: (7)

i can almost stay for certain it's what deanshark already pointed out. this is very common on first gen LS.

THXDOC

Ok- I'll inspect and repair any loose or broken wires in the trunk hinge. Crazy to think how a wire in the trunk would keep the transmission in park but if it was easy then everybody would have one of these cars right?

Gene01

You might want to monitor the voltage at the cigarette lighter socket to determine if the alternator is working correctly. You can either use a standard DMM (easier if you have a cigarette lighter adapter) or buy one of the very cheap digital voltmeters built into a lighter plug. I think I paid about $3.00 for mine (with free shipping).

deanshark

Crazy but true. Use the search feature at the top of page and, like I said before, search for broken wire on trunk hinge and you'll see how often that wire harness is talked about and 90% of the time it is the fix for crazy electrical problems.

THXDOC

I'm leaning towards the alternator. Here's why- when I fully charge the battery this problem goes away. I think there is inadequate amperage being delivered by the alternator, and thus insufficient power to these accessories. When the rpm's come up, the devices all function leading me to believe it's a weak alternator. I will check at the lighter socket as suggested. Thank you all for the suggestions, it's nice to know we don't face these issues alone.

Gene01

With the car running, it should measure above about 13.6V at the lighter socket.
With the engine off, it will read above about 12.4 or so if the battery is reasonably fully charged.

LScowboyLS

If alternator is bad, it has likely ruined the battery as well by now, and the likely reason that your alternator has failed is power steering fluid leaking on to it, which will kill the new alternator in a few months if the source of the leak is not addressed.

Sorry to be the kill-joy tonight

THXDOC

BINGO- found it- Corrosion in the 120A Alternator circuit breaker posts (found in the second fuse block under the hood). When the rpm's rose, the current apparently jumped the corrosion. At lower speed, not enough to arc. Cleaned it up and all is well again.

Legender

Glad you found it... know that's a relief...and thanks for posting what you found so we're all a little more educated...