80 with 1HDT Low Alternator Output

[carbon60]

Factory alternator and wiring. (This is a 12V system, two batteries in parallel, flips them in series for 24V starter.)

I noticed that my alternator is barely charging, so I measured a few things:

1. At idle, in drive, at a stop: all the dash warning lights come on; go out when pulling away or even giving it a touch of throttle.
2. At idle, with lights and fans on, 12.2V on the alternator post and 12.0V at the battery positive, to battery negative. Seeing around 7-9A using a clamp meter.
3. Testing: 1200 RPM, headlights and fans on. Measure 12.5V at alternator positive post to battery negative and see 17A with a clamp meter.

I'm fairly certain that I have measured 30A at idle in the past and have had no issue pulling two batteries back to full charge driving home from a 3-4 day camping trip, running a fridge.

What do you folks think? Bad regulator or alternator? Ground problem?

 

[bug616]

Typically the regulator on 1HDT

 

[landtank]

Check all your connection at the alternator and ground on the block.

Just for info, I have a brand new alternator that I ordered for someone but didn’t take it.

12v 110a 27060-17180

 

[nickolai]

Before you order a replacement alternator you need to work out which one you have.

There are two styles of factory 1HDT alternator, but most of the aftermarket Alternators are listed as fitting, when they don't.

Some early HDJ81s (up until at least 1994) had a "small body" 60 amp alternator. The problem is that the larger 100+ amp alternators, whilst fitting the cast bracket, do not fit the adjusting bar. In order to use the bigger alternator you need to swap to the adjuster bar 16381-17020 for the larger alternator. This bracket is retained by 2 of the water pump bolts - I have replaced these brackets without disturbing the gasket seal but your results might vary.

 

[carbon60]

Maybe it’s a battery: I connected my Victron charger and it basically didn’t do much at all.

 

[Sacho]

similar issue in my 80 series i have tried all; the solution was changing the carbons of the vacum pump, a guy told me alt worked through this vacum pump, i allways thougt that it was the alt or a electrical problem changed 2 alternators already with no solution until now; im enjoying the solution.

 

[mudgudgeon]

similar issue in my 80 series i have tried all; the solution was changing the carbons of the vacum pump, a guy told me alt worked through this vacum pump, i allways thougt that it was the alt or a electrical problem changed 2 alternators already with no solution until now; im enjoying the solution.

Alternator and vacuum pump are completely separate and unrelated in 1hd-t.

Earlier cruisers used a combined unit