Alternator/Battery warning light question
Discussion
Hi all,
Back again with my delightfully temperamental 280i.
My battery warning light has been playing up recently. When I turn the car on, it lights on key turn, but recently has started staying on while idling.
Once I pull out and start to accelerate, it goes off and stays off.
Additionally, if I rev the engine up once, even while stationary, the light will go off and stay off.
I've run some tests. I turned it on and disconnected the battery while the warning light was still on. This killed the engine dead. Dead alternator, right? Not so simple.
I then turned it on, and revved it till the light went off. Then, allowed it to go back to idling, disconnected battery again. This time the engine did not die, but stayed idling.
It's a bit weird, because if the alternator was bad, you'd expect it to stay bad when at idle, not fail to work for a bit but then magically work after you've driven it a bit. Anyone else had any experience with this?
I think i might just replace the alternator. Anyone can confirm for me that this is the right one? Attached a picture of mine below (think mine is missing the back casing).
https://www.ebay.co.uk/itm/202924477422?ul_noapp=t...
PS - Also noticed a wire was disconnected from the engine. Included pictures below. Bit weird, but didn't seem to do anything at all. Anyone know what it is? Doubt it's related but just in case.
Back of my alternator
The wire (previously disconnected)
Back again with my delightfully temperamental 280i.
My battery warning light has been playing up recently. When I turn the car on, it lights on key turn, but recently has started staying on while idling.
Once I pull out and start to accelerate, it goes off and stays off.
Additionally, if I rev the engine up once, even while stationary, the light will go off and stay off.
I've run some tests. I turned it on and disconnected the battery while the warning light was still on. This killed the engine dead. Dead alternator, right? Not so simple.
I then turned it on, and revved it till the light went off. Then, allowed it to go back to idling, disconnected battery again. This time the engine did not die, but stayed idling.
It's a bit weird, because if the alternator was bad, you'd expect it to stay bad when at idle, not fail to work for a bit but then magically work after you've driven it a bit. Anyone else had any experience with this?
I think i might just replace the alternator. Anyone can confirm for me that this is the right one? Attached a picture of mine below (think mine is missing the back casing).
https://www.ebay.co.uk/itm/202924477422?ul_noapp=t...
PS - Also noticed a wire was disconnected from the engine. Included pictures below. Bit weird, but didn't seem to do anything at all. Anyone know what it is? Doubt it's related but just in case.
Back of my alternator
The wire (previously disconnected)
Hey Penelope Stopit
First off thanks for the warning - good to know, I'll not disconnect it while running again. Last time I follow random instructions off the internet.
Re the feedback on the problem.
The light seems in good order as it is coming on and turning off with a half turn. I've recently replaced and tightened the belt. The earth and positive i'll check tomorrow, but otherwise sounds like I just need a new alternator eh. I'll pop one in just to to be safe - got an MOT coming up.
Cheers for the advice!
Best,
J
First off thanks for the warning - good to know, I'll not disconnect it while running again. Last time I follow random instructions off the internet.
Re the feedback on the problem.
The light seems in good order as it is coming on and turning off with a half turn. I've recently replaced and tightened the belt. The earth and positive i'll check tomorrow, but otherwise sounds like I just need a new alternator eh. I'll pop one in just to to be safe - got an MOT coming up.
Cheers for the advice!
Best,
J
Thanks all for the advice - i've ordered a replacement. As far as I know the one on there now could be 40 years old so it's time for a change.
As a post script - did anyone know what the wire that I photographed? The plug has started to disintegrate so i'll need to replace that too, but I have no idea what to start looking for.
Cheers,
J
As a post script - did anyone know what the wire that I photographed? The plug has started to disintegrate so i'll need to replace that too, but I have no idea what to start looking for.
Cheers,
J
Hi Adam,
When you say 'on a 280i you need a V6 chap' i'm not entirely sure what you mean. Do you mean I need a different alternator - or are you talking about the plug? If it's just bog standard that's great though, thanks - sensor makes sense, could be the temp sensor as it goes in by the coolant pipe.
When you say 'on a 280i you need a V6 chap' i'm not entirely sure what you mean. Do you mean I need a different alternator - or are you talking about the plug? If it's just bog standard that's great though, thanks - sensor makes sense, could be the temp sensor as it goes in by the coolant pipe.
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