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[Raeturbo]

I’m with brushes👍

[iansoutham]

Have tested the lead by basically disconnecting both ends and applying copious amounts of current through it. Although not loose, the battery end did get “warm” so I would say something there for definite. It seems to be that the light comes on dull for a few minutes after start up before slowly going out unless lots of equipment turned on.

[Doctor Gollum]

The light is a charging light not a battery light.

A reduced amperage means an increased resistance for a given voltage... V=IR and all that jazz.

[iansoutham]

Update…

It is definitely NOT anything alternator related.

I swapped the alternator out for another known good one (borrowed off a friend who has an X20XEV Cavalier that had literally just come home from work in it) and still doing exactly the same thing. I will bench test my original again, just to be belt and braces. I did put a regulator pack in it about a year ago.

I also put a jump lead from the alternator B+ to the battery directly (with the original lead still attached) and again, no difference.

I will take the car into work this weekend and deep charge the battery off the car and then use our warranty-spec battery tester to get a “real world” condition report (full computerised that we have to have for our warranty claims to BMW) on that as well.

[Raeturbo]

Bad earth?

[iansoutham]

Bad earth?

Can only double-check.

This light has been random for a couple of years and many things have been apart and rebuilt in the meantime so I would like to think not?

Quick question as I have not looked too far at it at the moment, the positive lead runs from the battery, across the top front of the engine and down in front of the alternator. It then splits to the alternator and the starter motor. What is the split? Soldered connection, runs from starter motor to alternator as a separate lead, other?

[Doctor Gollum]

It's two separate leads in a common wrap if it's anything like the V6. Which it sounds like as the routing is pretty much identical. 

[iansoutham]

Definitely 1x larger lead off the battery terminal than what is at the alternator. I know onFords they run a lead to the starter and then a separate one from that to the alternator, just hard to take it a part in the dark at the end of a driveway.

[cam.in.head]

if you have tried a lead from the alternator direct to the battery (battery rather than anything else)then you have already eliminated anything positive cable wise so its either a bad earth connection ,a short somewhere on the charge light lead or a fault on the dash.
especially if you dont actually have any charging issues or obvious faults.
i would have thought due to the volt drop alternator to battery then adding the extra cable would have shown up the cable or connections but apparently not.

[iansoutham]

Well…..

Alternator double-checked and all good. All positive leads I can get to cleaned up. It would appear that the X20XEV runs a cable to the starter motor and then a drip lead back to the alternator. The starter motor connection is the only one I have not managed on the positive side.

On the earth, it goes straight from the battery to the bracket behind the PAS pump that holds the aircon pipe. The “stud” looks like it may be the culprit as someone (not me) has had it apart and then done it up allowing the connection to twist right round and bend. All removed, earth connection cleaned up and straightened, along with the stud getting a drop of thread lock to hold it in place (it turned instead of the earth but when trying to undo) and everything reconnected after cleaning.

Whole 0.2V drop now from alternator to battery, no battery light at the moment and only glows slightly with aircon, headlamps, front and rear fogs, heated rear window and both heated seats on, then goes out as soon as heated seats switched off.

Will find out tomorrow for certain. Will also take starter connection apart Saturday when I take car into work to do oil change on the ramps and charge/test battery as access is only from underneath.