electrics gone a bit random query...

[ceebeedee]

Hello All - Happy New Year...

Feels like I have a dodgy earth issue but I thought I'd throw this up on here to get any other opinions..?

Took the Elise out for a spin to Kenmore yesterday - didn't make it back to Pitlochry without a tow back from an indulgent friend in Aberfeldy - eek..! The car died with full beams and heater on, the red battery light came on and then it was dead as a dodo within 3 minutes.

On being back at home I'm seeing a number of issues - maybe I have some dreadful multi-point failure going on.

First thing to say is that the battery is 3 years old - and the car never gets used enough, so it is probably spending too much of it's time at low ebbs...

The two front headlamps (low beam) seem to have blown...

Multimeter was initially showing only 10/11V at battery on idle. Examined the alternator wiring and the cable fell out of the plug on touch. Connector and insulation gone brittle from proximity to exhaust heatshield. Aha, i thought - sorted. So I spliced the cable back and rewired the connector with some short lengths of new cable - it then shows 13.5V on idle. I was pleased. Then, on load (full beam + blower) the reading dropped back to 9V - revs increase makes no odds. So, less pleased - not sorted...

Then the funny business started - immobiliser and alarm going off randomly. Car will /wont start. Headlights turning on themselves. The Stack LEDs going "disco". The scenario is now so random that I'm struggling to find anything repeatable in the behaviour. Or maybe I've lost by ability to be analytical...

I've tried experimenting with temporary earths from battery to engine casing / bracketry - but again it all just seems a bit random and I'm struggling to see a pattern...

At this point on Hogmany - all pointers welcomed. Perhaps I'm looking for someone more knowledgeable to suggest an order of attack...

Thank you...

[David]

To me all these 'faults' fit the classic loss of regulation - probably due to the loss of the reference voltage to alternator (connector problem). You've probably caused an over voltage. I'm sure some of the guys with better knowledge of your car will be along to point out what needs to be checked - but the battery might have been damaged, if the fault was there for a while.

[dirkpitt]

hi

try recharging the battery right up externally and refit or re connect, then see how you go......if the problems return then a new battery would be a good idea...an besides it always good to have a spare IMO.
i remember the old man would have a flat battery by summer for his old MG midget and would have to really charge it up to get the car going again, however...the battery never really recovered from being flat for a long period of time........it never held its charge for long and he had to change in the end......
hope, its that simple.......keep us posted

[ceebeedee]

Thanks for responses so far chaps - I'd put the battery on the bench and it's charging as we speak, Regardless - I'll tackle it all next year..!

Hard to tell what the prognosis on it is - but I have a sneaky feeling a new one will be on the way - at least.

Fingers crossed that it's that simple...

[robin]

It's not the battery. The car will run from just the alternator assuming you can get the engine started in the first instance.

Is it S1/S2? I'm assuming K-series.

If it's S1 then check that the battery cannot have slid across and touched the chassis, though it doesn't sound like that in this case.

If it's S2 be sure not to reconnect the battery with polarity reversed now you have removed it - that creates all sorts of additional woes.

When the battery is fitted then turn ignition on but don't start the engine. Does the battery (charge, actually) warning light come on? It should. Now start the engine. The light should go off. If it fails to come on in the first place you've lost the charge control wire to the regulator, or the regulator is bust. If it fails to go off, the regulator is bust (assuming alternator drive belt is fitted). The regulator tends to break when the engine is under load and the control wire fails; this creates a surge current that blows the diodes in the regulator. You can repair by fitting new regulator if you can source one or you can exchange the whole alternator.

You should probably check all the fuses in the normal fuse box and then those next to the ECU too.

Cheers,
Robin

[ceebeedee]

Robin,

thank you for fab, helpful message reply. I've not been able to look at this until today. As you suspected, fresh battery in, key in, start engine, light stays on...

Fuses seem OK.

Looks like I'm on the hunt for a regulator and connector. From a cursory google session, they seem hard to find. Even alternators aren't ten a penny. In fact, some cost as much as £300..! I wonder if this a special item or is it possible to use units from other k-series motor like an MGF or Rover 25/45.. ? the connector onto my alternator is certainly marked BMW.

Thanks to this amazing forum again..!

[BiggestNizzy]

Pop into your local scrap dealer. he'll have one

[ceebeedee]

Poor wether and lack of motivation meant I pushed her into the garage afew weeks ago.

Better weather and half term hols means that I've now got an new Alternator fitted. Sorted newer wiring into the old connector (couldn't find a new connector to match...) and hey presto we're back in business...

Just need to figure out why all the headlight bulbs seem to have blown all at once in tandem with this. Doesnt seem to be the fuses - hmmmm...

Many thanks again to all, particularly Robin, having seen what a huge a contribution you make to this board on all things electric I'm delighted that you cast your eye over my post - Cheers

[robin]

I suspect you got overvoltage during the initial failure - it's possible that the regulator pack let go in a spectacular fashion. I would find the cheapest bulb, plug it in, spark it up .. bet it doesn't blow.

[ceebeedee]

all sorted - new bulbs went in a treat (after I figured out I have to remove front wheels to get into them - lol

thanks again..!