sierrafery
Well-Known Member
The light is connected to the alternator's small connector through that square grey connector near the ECM so if the light was on while you've got that 14.3V reading might be a bad contact on the circuit cos the light comes on when it doesnt get feed but if the light comes on randomly while driving and you can't confirm the voltage can be an intermittent alternator failure too?
Thanks, I have a voltmeter plugged in permanently so hopefully would be able to see if it was not charging while driving. I will have a look at the connectors near the ECU. After leaving it running for a few minutes the light went out and did not come back on so I should think it is a connection somewhere. Presumably as long as it is physically charging normally it is safe to drive?
This one?
sierrafery
Well-Known Member
That doesnt look square to me and i think it's closer to the fusebox than ECU, it's C0162 i meant, pin 2 brown/yellow wire
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Is your tacho working OK?
sierrafery
Well-Known Member
It's a D2 not 300tdi
See! Did it again! You are always on your toes!
(And I get confused, old age I'm afraid!)
(And I get confused, old age I'm afraid!)
Yep I found it shortly after, connections seem good and no bare wires etc. It seems to just stay on for a few minutes then goes out. Presumably as long as it is physically charging normally it is safe to drive?
sierrafery
Well-Known Member
Did you check the small plug on the alternator too? anyway watch the voltmeter, if that shows above 13.5v while the light is still on you can drive it without fear but if the voltage climbs slowly as well then the alternator is on it's way out IMO
I managed to get the plug off the back of the alternator earlier and using a power probe could reliably put the battery light on and off. To me this rules out wiring in the vehicle?
The battery light does seem to go off after a few miles of driving and doesn’t come back on until the vehicle has been left a while. I am wondering if it’s a sign the alternator is on it’s way out?
No, the alternator is perfectly fine........... right up until the moment that you really, really, really need to get home and its getting dark and you need your lights on and there's a traffic jam on the motorway and its cold and raining.
THIS is precisely WHEN it packs up. Up until this point it will be fine.
THIS is precisely WHEN it packs up. Up until this point it will be fine.
sierrafery
Well-Known Member
Unless it's a bad contact which reacts to vibrations... the relevant test is to watch the voltmeter while the lamp is on
As in a bad contact within the alternator? That’s what I’m thinking
sierrafery
Well-Known Member
If it's within the alternator the voltage should be down too when the light is on unless it's only on the lamp's path
it had a new regulator/rectifier like in the link below about 6 months ago, maybe it’s that that’s not quite right.
https://www.ebay.co.uk/itm/254393727733
if I’ve got the right wire on the connector you showed I’m getting 13.1v on it, 14.4v at the alternator and 14.3v at the battery and at the fusebox.
sierrafery
Well-Known Member
If you get 13.1V on that NY wire while the warning lamp is on the problem should be the wiring or instrument pack cos the warning lamp comes on when the voltage on that wire drops below 7V
