Battery light on even after new alternator?

[Jonesy_sa]

Hi

Replaced the alternator as it had a suspected dropped phase and noisy bearings. The charging light was always duly lit which I attributed to the alternator (I'm told this can happen with dropped phase).
However, new alternator installed and it's still partially lit. Further, if you apply the handbrake the charge light lights fully in sync with the handbrake light.
I've checked and it's charging correctly.
Any ideas?

[0-TJ-0]

Earthing issue is my bet.

[Jonesy_sa]

Which earth's are relevant? And how do I check them?
The loom for the alternator actually has a small earth cable. Any idea where that goes?

[0-TJ-0]

I honestly don't know specifically. Odd electrical issues can regularly be traced to earthing problems. If it were me I would run through the engine bay, disconnect and clean all the earths you can find.. there is one directly off the alternator from memory.

Won't hurt to check them anyway. Good starting point. If it's not that hopefully someone with a bit more knowladge will chime in haha

[mudnut]

Yep, add a couple earth leads from the block to the chassis and chassis to body. Use a bit of WD40 on the existing lead connections.

[Jonesy_sa]

I may have found the problem?
I was checking voltages between batt and various body/chassis points and all seemed very good.
However noticed the auxiliary battery was not charging. I ran a lead directly from the main battery to solenoid (isolator) to activate it. When I did the dash charging light went out.

I can't fathom why this would cause the warning light issue; ideas?

The dual battery system seems very basic. I need to chase the wiring down as it disappears under a few things. Anyone know how these should be wired? I generally only activated when the car was running, not just with ignition on.

[0-TJ-0]

Autoelectrics are a wonderful thing. Sounds like something isn't wired quite right. Reckon you're onto it re-doing the second battery system.

FWIW checking your voltages without load across different parts may not show you a bad earth. The issue can be in the current draw over them or lack thereof. For instance, I had to fix a rear 12v plug in mine when I got it.. showed similar(same minus .1 or .2 of a volt)voltage to the battery but wouldn't run a fridge. Turned out to be a bad earth lead from the battery.

[MB]

Probably not much help maybe, was mucking around with higher output alternators on a chev modified GU 4.2 host and found that same annoying light only at chev 550rpm idles?
Found once it needed a better 750rpm original ‘tickle up’ wise to trick it off.
One of the earlier muck around alternators was playing with I do believe gave same symptoms from a half arsed myself lazy earth to the water pump housing area maybe, unsure bad memory:-)



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