Plume of smoke then nothing....

[mcbonio]

Ok so just got in my car to go out, started it and after maybe 10 seconds there was a big plume of smoke from under the drivers kick panel.! Then over a space of a minute the idle speed started to get slower and slower until the engine stopped.!

Now when I turn the key all the dash lights come on, but it won't even crank. I've had a quick look at the wiring under the kick panel and the ECU, can't see any signs of melted wires or anything.

What has happened?

[Brianmoooore]

See if it cranks from the diagnostic socket.

[mcbonio]

Ok its starts now, idle is low and lights are a bit dim. The cluster back lighting is no longer working yet the heating controls and clock back lighting works.

I've found a melted wire, its a 2 pin wire from the abs bulb on the back of the clocks which was disconnected It was loose behind the dash and I think it's shorted on something metal behind the dash.

I think its burned something out as the car doesn't seem right. Could it of flattened the battery?

[mcbonio]

Ok just tested the battery, standing charge is 11.8. Just put it on charge. Could a short discharge the battery like that?

[mcbonio]

Ok left battery on charge over night, tested it on the car, working like normal.! Strange!

[Brianmoooore]

Wait and see if it stays charged before you sign it off, 'case closed'.

[mcbonio]

It seems fine, only issue are the cluster backlights, they don't come on right away, the take about 2 mins before they finally come on. Not sure what's up with it.

[Brianmoooore]

What's (was) the colour of the melted wire?

[mcbonio]

Don't know, its totally melted, the other wire in the same sheath is grey and red.

[Brianmoooore]

Grey/red is the 'live' of the panel lights, not the ABS light. The other wire would have been brown/white, and if power is applied to this wire, as seems to be the case, you will probably destroy the rotary dimmer that is part of the headlamp switch.

[mcbonio]

Are you sure? The burned connector and partner wire are no longer connected and never were, yet the cluster lights come on after about 5 mins of driving. Usually one side of the clocks then the other... strange?

[Brianmoooore]

I can't say exactly what's happened in your particular case, from here, but a grey/red wire in the front of the cars cabin is definitely an instrument panel/switch/ashtray/etc., illumination live feed, not anything to do with ABS, and if a voltage source capable of providing a highish current is applied to any brown/white wire in the same area, damage to the rotary dimmer is likely to occur, unless the dimmer is turned to full brightness.

[mcbonio]

Yeah it wasn't the ABS light, i'm going to have a dig around and get the dimmer switch out over the next few days, have a look.

The melted wire is still functioning but is now bare copper, I will see if I can trace it to its origin and replace it.

Cheers Brian, a massive help as always.!

[mcbonio]

Ok so there is still an issue, went for a drive, car seemed fine. On the return journey home the headlights and dash lights were very dim from the moment I started the car. I stopped and revved the car hard and all the lights suddenly became very bright again and seemed to stay bright for the rest of the journey.

I tested the battery,
Running charge 13.5
Standing charge 12.5

Any idea what this might be, Brian?

[Brianmoooore]

First thing I'd do is take the air filter/AFM out of the way, then whip the regulator pack out of the back of the alternator, and check the condition and length of the carbon brushes,

[mcbonio]

Mines an m30 remember, I think I can get to it without removing anything.

What am I looking for Brian? How can I tell if they are ok or not? Also, you think my short circuit issue might have caused this?

[Speedtouch]

Alternator brushes usually start out life approx. 10mm (1cm) long, but the outer one usually wears alot quicker than the inner one (due to more friction), and when it gets down to about 3mm or so, the connection to the slip ring becomes intermittent, causing poor charging and often a flickering ignition light.

A short circuit may exacerbate a failing alternator. You should really try to find out exactly what caused it to short, otherwise you may not be so lucky the next time, and end up with your car going up in smoke!

[mcbonio]

Yeah the short was a grey/red wire and another wire which is melted and bare. Both had spade connectors and were together in a black plastic sheath. They were loose/disconnected behind the dash and I somehow grounded them on something when tidying the relays around the steering column.

All the dash illumination / dimming still works.

[Brianmoooore]

Thinking about this further, this COULD be the ABS warning light wires. The usual colour for the wires are green/red and green, but I've a handwritten note on my circuit diagram giving grey/red and green as alternative colours.
If this is the case, the melted wire would have been green, and is unfused switched ignition live. This would certainly cause some smoke if it was shorted to earth.

[mcbonio]

Don't know if it was ABS as that is still plugged into a bulb and is working.

Whatever it was is was unfused! I'll check the alternator brushes today, this dim light issue could be unrelated to my short.

[mcbonio]

How many volts should the alternator be putting out at idle?

[Speedtouch]

Around 14V when charging.

However, if your idle speed is too low, it may not kick in with any charge unless you blip the throttle.

[Brianmoooore]

This problem seems to be of an intermittent nature, so measurements are unlikely to help, unless connected up to a data logger. That's why you need to physically inspect the brushes.

[mcbonio]

I can't see how to get the regulator pack out of the back of my m30 alternator. Is it those 2 nuts with wires attached?

[Brianmoooore]

If it's a Bosch alternator, similar to that found on OE E30 engines, the regulator/brush pack resembles an old TO3 power transistor (round; about 25mm diameter) and is held onto the rear of the alternator by two screws.

[mcbonio]

Yeah looks like I'm going to have to take the alternator out to have a look as one of the screws is directly behind the oil filter housing.

There is an issue there as when I start it up the engine runs like its on 5 cylinders until I blip the throttle past 3k, then it idles smoothly.