Roler

Charging issue

G'day

It's been a while here, hope all are keeping well
It was a while for the XJ too
Had been sitting a few months, so charged the battery overnight, did some pre-start fuel conditioning and started up.

As the engine was idling, did some testing in the engine bay and noticed by battery voltage being below 12.4
Putting load on it, made it even go to 12V. Jeep kept running pretty much normal during this.
Increasing the rpm's would bring it up to 13.8 Volts (it never has charged over 13.8V either in the past 12 years, even with the previous alt in there)
Letting it idle back down would drop the batt voltage again to below starting voltage.



- 2nd-hand alternator from the junkyard, about 2 years ago.
- Cleaned up all the engine bay grounds, including the 2 on the coil mount
- Did a load test on the battery, reading remained within good range.
- Did voltage drop test: No voltage drop over the positive or negative side between alt and battery
(about 0.006V)
- B-terminal output reflected batt voltage running idle and with increased rpm's.
- Gave the alt a few loving taps, in case something had to "free up". Or just because that usually fixes half the issues with this ride.



So in short: alternator appears to not charge the battery at idle, but seems to be able to put out enough when raising the rpm's
Voltage regulation ( by the ECU) could possibly at fault, but I understand this would be less likely; it would mean that only at idle the ECU doesn't tell the alt to start charging?

Alternator the cause, despite it being able to put out enough umph with increased rpm's?
(Not sure yet how to check the ECU voltage regulation for the alternator at idle)

Thanks for your input

Cheers

Philippe L.

In my experience: when an alternator doesn't charge the battery (voltage too low) when your engine is idling, the alternator needs replacement.

cruiser54

sure. Only show up when you need something!! LOL. Great to hear from you.
Have you been driving the Jeep anyway?

Rogue4x4

Welcome back Roler.

It's quite possible your alt is starting to go south, especially if it's a salvage. Things like that are hard to pin down. I suggest you find someone semi local to rebuild your alt, buy a refurbished one, or just get a new one.

JY parts are always a crap shoot, might get you by, but there's miles on salvage parts you can't account for. Great in a pinch, but longevity is sacrificed.

My perspective. Welcome back.

Roler

I'd prefer the term "posting with purpose " or "reasons to visit old friends" LOL

Glad to see you still here, Cruiser, I really am. I didn't know what to expect with the way the world is atm
Good to see you still supervising the flock. Although I expected your post count to be over 50K by now so you obviously gotten a bit slack in my absence

I haven't driven it at all the past months, it has not been my daily driver anymore for a few years now
I guess technically I can drive it the way it is now, just cant let it idle..

Roler

Thanks mate

Yeah I have hardly ever bought junkyard stuff, also because I haven't got many around here that have XJ parts.
But its always a gamble.
Option of having a shop rebuild my previous one might be an idea, I hadn't thought of yet. Was still in the diagnostic phase of the process!

Good to see a few familiar names starting to pop up again

cruiser54

A few of us hang around like a bad smell....

could you remove the alternator and have it tested?

Roler

Ha! my smell hasnt returned fully yet after my covid experience a few weeks ago
the only thing that was preserved was the smell of Vegemite on toast for some reason lol

Yeah good idea to try. We don't have the parts stores here that do alt testing like in the US but surely I should be able to find a local guy that could have a look.

Bugout4x4

I am only jumping in here because it could be an issue I have run into several times. How long has it been since you put a new belt on it? I have had them wear the grooves to the point they no longer grab enough traction to spin the alternator fast enough at an idle. They end up riding on just the very points around the pulley and have no grab at all down in the V grooves themselves. And they don't always squeal or make any noise that would alert you to a slipping belt.

cruiser54

How do you differentiate the difference in smell Vegemite vs Fart?

Roler

Differentiate the difference hehe

One smells like home ( or makes the neighbourhood dogs howl)
The other is Vegemite

cruiser54

That's Oz slang, ya know.

Roler

I should edit that answer, after all there are many differentiating differences to differ there between them. And yet again, not. LOL
But we digress from the thread here, P!

Roler

Trying to find some info about how to check the ECU'S 'signal' to the alt to tell it to start charging. Probably probing some connection at the ECU or at the alt (or both) I reckon, to get some voltage reading. Just would like to check this as part of the diagnostic process to make sure that's good before condemning the alt (again) .

FSM states for the EVR (voltage regulator) to "refer to appropriate Powertrain Diagnostics Procedures manual". Have trouble finding it, is that part of the FSM?

cruiser54

I think I have a paper version of 91 or 92