Flat 6

Flat 6

Member
Gawd I hate electrics.

So I’ve just changed my alternator to a new higher output one as recommended in here. With old alternator the battery was not getting a charge but there was no charge warning light.

With new alternator the battery is still not getting a charge but charge warning light is on.

Where do I go next?

A
 
Flat 6 said:
Gawd I hate electrics.

So I’ve just changed my alternator to a new higher output one as recommended in here. With old alternator the battery was not getting a charge but there was no charge warning light.

With new alternator the battery is still not getting a charge but charge warning light is on.

Where do I go next?

A
Click to expand...

How's the condition of the wiring ?

I'd put new leads on to be fair ...
 
Connections seem fairly standard, certainly no changes made since alternator has been charging OK. Connections to alternator were in block originally with three connections. Two of the wires push onto thicker blade connections. The third goes to a smaller blade closest to engine block. I think the smaller connector had become disconnected because the plastic holder wasn’t holding it in place. So I cut off that end of the plastic block and that thinner wire is just pushed on directly. I think that thinner wire is the one that goes to dash charging light? Al
 
Flat 6 said:
Connections seem fairly standard, certainly no changes made since alternator has been charging OK. Connections to alternator were in block originally with three connections. Two of the wires push onto thicker blade connections. The third goes to a smaller blade closest to engine block. I think the smaller connector had become disconnected because the plastic holder wasn’t holding it in place. So I cut off that end of the plastic block and that thinner wire is just pushed on directly. I think that thinner wire is the one that goes to dash charging light? Al
Click to expand...
Yes smaller wire should be charge light one.
 
And does the red light stay on when running , have you measured voltage on battery when engine running
Have you got 12v on the thin lead when it’s disconnected from alternator , red bulb should come on when you earth the thin lead
 
Last edited:
steve2286w said:
And does the red light stay on when running , have you measured voltage on battery when engine running
Have you got 12v on the thin lead when it’s disconnected from alternator , red bulb should come on when you earth the thin lead
Click to expand...
Yes, red light stays on when running

Voltage on battery is 12.3v at moment and doesn’t change when engine revs. To be fair the battery hasn’t had a charge for many starts and a 5 mile test drive with red light on so not surprised it’s only 12.3v.

12.3v also on thin alternator lead when disconnected and yes, red light comes on when that lead is earthed.

Did I read somewhere that the alternator won’t charge the battery if that thin lead has become disconnected from alternator? I am wondering if my old alternator was actually OK and the thin wire was actually not in place. When I pulled the plastic wire holder out of the alternator the spade connector on the thin wire was not properly seated in the plastic connector and I think it is possible that it wasn’t on the alternator at all. Might have a duff replacement and might test by putting old unit back in.

Photo of existing wiring and plastic holder attached.

Thoughts? TIA.

Al
 

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Thin cable excites the alternator to make a change.

So light should be on with ignition.
Once running the charge should turn out the light.

Make sure little cable goes on little connector. The 2 large lugs are joined
 
Looks like your charge light lead is ok, think it does need that exciter voltage to get charging
Can you crimp in those big connectors a bit to get a tighter fit on the spade terminals also do this on the small one to make sure .
You will have checked the belt tension by now, giving about 3/4” movement on the longest run between pulleys.
Is the earth lead got good connection between engine and chassis
You might be able to remove the spades from the connector and fit directly to alternator , give spades a clean if you can too.

The light goes out when the 12v charge coming out of alternator “cancels out” the 12v coming from bulb wire as I imagine it
 
OK, thanks guys. Good to hear that the 12v thin wire is doing its job.

The engine is earthed directly to the battery neg terminal which is earthed to the side of the radiator casing. None of this has changed since the battery was getting a charge so I’m still thinking the issue is with alternator.

I guess the thicker brown wire goes to the solenoid and on to positive battery terminal. What does the thinner brown wire do?

Will swap back in old alternator this weekend making sure all connections are as clean and tight as possible. Will report back.

Al
 
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