Wiring Loom Short Circuit, Perhaps?

[Jack Pritchard]

Ok, so I changed my alternator

http://www.lexusownersclub.co.uk/forum/index.php?showtopic=80095

and all seemed ok for a couple of days but then, the Saturday before Christmas I was driving at night to pick my daughter up when suddenly the dashboard lights dimmed as did the headlights and I had a sudden loss of power.

I managed to pull over to the side of the road and switch off where I was greeted by a huge plume of smoke coming from the bonnet, roughly where the Battery is.

Roadside recovery came to my rescue and as soon as he connected his jump starter to the Battery smoke immediately started to rise from just below the Battery. Although it was pretty dark so we couldn't tell exactly.

He told me that I had a short circuit in the wiring loom somewhere and it would cost a fortune to put right. Not being the sort of person who likes to be defeated my questions is this. Is there anything I can do about this myself? I've had a really good look all over, both under and above and have even taken the fuse box apart but can't find any obviously melted wires or anything that looks like it has recently been pouring out smoke.

So what can I do apart from get a mobile mechanic around?

Thanks :)

[steve2006]

Most electrical circuits are protected by fuses, the main alternator supply normally has a 120A fuse to protect the high current loom.

What was the reason for replacing the alternator? I would start there and work backwards from it, the only circuit not fused is the starter motor supply and the cable for that is routed around the area where you saw the smoke.

You either need good electrial circuit experience and a multimeter ot a decent auto electrician.

It does seem strange that there is no physical evidence present after such a burn up but the problem could be buried in a large loom.

Not recommended but you could recharge the Battery and then just touch the positive connection back on whilst looking for the source of the smoke then immediately disconnect it.

[Jack Pritchard]

It's funny you should say that. I've been having problems with the starter for a few months now with it either just clicking or failing to start the car when I know full well that the Battery was fully charged.

Also, the mechanic was surprised that none of the fuses blew and if you say that the smoke was coming from that area then this gives me hope that I might be getting closer in tracking the problem down. Perhaps I can't find any smoke damage to the wiring because it was the starter itself that was causing the short circuit and was smoking.

I changed the alternator because it simply stopped working and I was, for a good few weeks, running the car on Battery power only and having to charge it up myself every night.

Thanks for this, I feel a bit more positive now

[TigerFish]

It could well be the starter sticking on, so I would start in that area. There is a tutorial in my sig for overhauling the starter, doesn't cover the removal of the starter though.

[Jack Pritchard]

I certainly intend to.

Forgot to mention that there is now zero power to anything, i.e. electrical system is dead and whenever i connect the Battery all I get is sparks and fizzing :S

[TigerFish]

Maybe the overload in the Battery has cooked that as well, might be worth hooking up another one just briefly to check that as well.

[Jack Pritchard]

Min update:

Disconnected the line that goes straight to the starter motor and as soon as I did that all the cars electrics started working again! So it's definitely that that's the problem.

Of course now I've triggered the immobiliser so I have to wait before I can fiddle around again but, so far so good :)

[steve2006]

That's good news then, I remember flattening the Battery on my 99 GS300 and had to go through the key in ignition proceedure to get the immobiliser reset.

At least the starter is reasonably accessible on the GS unlike the LS so replacement is fairly easy.

[Jack Pritchard]

I've just located the starter and I must admit that it looks very buried and tricky to get to. Any tips?

[TigerFish]

Unfortunately, on the mk1 GS300, it is a right pig to do. I used lots of extension bars, wobble bars and U/J's to go right past the gearbox from the propshaft end to get it off when I did the overhaul tutorial. Not as bad as the V8 GS's or LS's, but much simpler on the mk2 GS300.

[Jack Pritchard]

I reckon that I could have just enough wriggle room to get to the starter if I moved the strut in the middle of this picture.

Question is, is this strut important? Will the engine suddenly shift or something if I temporarily move it out the way etc.

It's so frustrating being able to see the bloody thing but not able to get to it!

[TigerFish]

I can't make out what it is mate :(

[Jack Pritchard]

It's a strut that goes from the air intake block down to the bottom of the engine. I'm hoping that it's just a stabiliser and that I can comfortably remove it to give me extra room to work in.