GeneralD

Hello fellow Lexus enthusiasts!

I come to you with a pretty ugly electrical problem....

To make a long story short, I believe that a jump-pack or jumper cables were hooked up backwards with the car's battery completely flat. After that it would crank but not start.

A bit more investigation revealed that about 3 fuses were blown - two up front, and another in the cabin. Upon replacement the car will now start and run, but is only running on the battery charge. IE: the alternator is not charging. Additionally many accesories will not function (gauges, radio, power windows, etc), and the transmission selector will not unlock from park.

Could the alternator's regulator circuitry have fried and caused all these other devices to not function? Should I expect replacement of the alternator to fix everything else, or does this indicate something more sinister is in play?

Any direction or sugestions you guys have would be appreciated....

What say ye?

Thanks,
Rick

esucaris1

As far as the accesories sounds like another fuse... as far as the charging system could it have had a problem already?

GeneralD

Ran fine right up to the point where it wouldn't start at all one day after a jump. And the fact that 3 fuses all blew at the same time....

Prior to that day the battery was weak, but once it was jumped it would stay running (off the alternator). Now when you pull the jumper cables the engine dies a short time later once it has drained the battery.

I've checked all the fuses with a MM, and they all check out good. There's a LOT of accesories (including all the guages, and backlights, etc) that aren't working. Perhaps a relay or something that isn't activating due to the alternator not working? Just a guess. I have no idea really - thus my post on here

Rick

lxgs4

have you checked your 140 amp alternator fuse? Last time i saw a car jumped backwards, there was about 10 fuses blown.

amf1932

You must have surely burned out the diodes in the alternator, so the first thing to check is the output from this component. If you determined that it's not putting out any voltage, and you replace it, you'll probably find that everything will be back to normal.
Most electrical accessories won't work when you just have the battery power without the alternator working. While you're at it, check out the condition of your battery(Load test), and the terminal connections(clean & tight).

guitarmike

no the alternator is protected by the 140amp alt fuse. No damage would have been done to the alt from the backwards jump. You do however sound like you have more blown fuses. Ie.. gauge fuse etc.. Not sure on what model car you have but it's likely that there are fuses blown under both the passenger and driver kick panels, and also under the hood. Make sure that you check all fuses. If the alt fuse up front is blown, if i remember correctly, it is screwed into the fuse/junction block up front, and will not just pull out. hope this helps.

powerwave

there's another fuse blown somewhere. the alternator fuse can still blow with a backward jump. just be glad you didn't backwards-jump a hybrid... it could always be worse!

amf1932

It's a known fact that using the wrong polarity when boosting a car that has a weak battery CAN burn out the alternator diode(s), even though you have fused protection in the circuit.