HJ61 - 12HT Charge Issues

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Jan 13, 2023
Gold Coast, Australia
Chasing a charging gremlin in a 89' HJ61 12HT (12V aussie model).

Back story:

Standard alt died 18 months ago, fitted a new 80A internal reg alt and it run without issues until a week ago. Charge & filter lights remained constant and not producing any charge. I already run a thicker gauge cable from alt to battery to compensate for the bigger alt. This setup has worked perfect for years, over some big drives powering DCDC charger and a few other accessories.

Swapped it out for a new Bosch 80A alt, installed fine and charged at 14.2V on startup....happy days... Left it to idle for 5 mins and when I came back the alt was sparking internally and starting to smoke! Shut the car off and inspected the internals through the reg cover, looks like I could see some damage internally.... not ideal! Haven't pulled it apart yet, but wouldn't expect a bosch alt to fail out of the box?

Removed the bosch and installed another brand new 80A alt, car runs fine but no charge. Charge & filter lights no longer show up with IG on, only appear if I put a test light on the charge circuit (charge lamp relay (CLR) pin 4, charge fuse - test light barely illuminates, is this normal?). Thinking when the bosch unit failed it has caused more damage through the charge circuit.

I've tested the CLR as per the FSM and appears to check out, tested continuity of the charge circuit wires and seems to be fine. Taken supply direct from bat to test and no difference. While running, the volts won't exceed 12.3V at battery and alt. I've added additional earths to alt, block and battery and made no difference.

- Is there a test I can do to bypass the internal reg to see if this is the problem?
- Seem to remember a post about being able to ground one of the alt terminals to bypass the internal reg?
- Can I bypass the charge circuit completely to test the alt?
- As the charge light doesn't illuminate on IG on and only when I use the test light (grounds the relay, illuminates the charge lamp), does this mean the ground for this circuit isn't working as the lamp stays off with IG on?

I'm out of ideas as to what to try next, any help would be greatly appreciated. no matter what I do and change, it won't produce any charge.


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