V40 2.0 Engine Managment light...hmmm
 

Hi people,

I stupidly left the interior lights on in my '97 V40 on saturday eve in a multistorey car park and when i returned to the car on sunday (1pm) the battery was absolutely flat.

As my brother had a trickle charge/engine starter unit in his boot we tried that. It plugs into the cig lighter of each car and after 20mins or so supposedly gives enough juice to crank. This didnt work so we bought some jump leads and the car started fine and ran perfectly as normal.

The odd thing is that the engine management light now flashes rapidly at below 1500 rpm but goes out as the revs rise. The car runs perfectly and ive now done 140 miles since with no change in performance/economy etc.

Has anyone had this problem before?

The cig lighter gave out a couple of sparks when the charge unit was plugged in and i wonder if this damaged the notoriously fragile electronics? My V40 is base spec; single airbag, no aircon etc and has never shown any warning lights before.

Thanks,

Joe

Arcing (sparks) when plugging in the charger can cause electronic problems. First off, now the battery is charged, disconnect it for half hour or so to try and reset everything. Next action would be to read the OBD codes (you will need a code reader for that).

Your 1500 rpm symptoms indicate to me that I think you have damaged the exciter diodes in the alternator, either with the cigarette socket lead or by the jump start, go to a auto electrician and get them to check the charge rate above and below 1500rpm, it will be low on charge below 1500 and above 1500rpm will look almost ok.
So your still charging the battery while driving but not at idle, if you get caught in heavy traffic you could end up with a dead battery.
Cheers George

Thanks for the great advice guys, i will disconnect the battery as suggested and see if it resets.

With it disconnected I guess i can also see if the alternator will run the car below 1500rpm with no battery (after starting the engine of course!) - that should show up any alternator issues....oops!

Great stuff,

Joe