Afternoon, all.

I've a problem with charging on my '87 2.6 Montero engine, and a not sure of the cause.

Around a week ago, the battery light started dimly lighting up and flickering on/off while the engine was running - it went totally off again while driving home. When I got home, the the voltmeter showed just under 12v... normal would be around 14v. I haven't taken the car far from home since, and now the battery light is on all the time the engine is running. The battery light dims down when I rev up the engine and brightens when the revs drop back down toward tickover, but doesn't go out at any revs. The voltmeter shows just over 10v now.
The car will start after standing for a while - there's enough power there, but will barely crank if there's only a short time between stopping/starting - when buying gas, for example.

The battery is a year old and I'm not sure of its quality, so I put a new battery on this morning, but the battery light still comes on and stays on when the engine is running. It fades with higher revs but stays lit up.

Aside from the alternator, could anything else be causing the battery light to stay on?

I'm reasonably sure the grounds are good as she starts very quickly on a charged battery and the lights work well, etc. - but I haven't removed and cleaned the grounds.

I fitted a new starter motor and starter relay 3 weeks ago after some starting problems and also put in a new cable from starter to battery - could that have had an effect somehow? - Seems strange the alternator bugs out so soon after I replace some electrical components on the car.

Any help greatly appreciated as I know zip about most things electrical.


Cheers

Rob

Check and make sure your alternator belt is tight and not slipping, but it sounds like bad alternator. Starter/Battery/Alternator are like a family. When one part has problems it can put a strain on the others. For example, a bad starter might make you crank a lot, which drains battery, then the alternator is overworked constantly trying to charge up a weak battery. So it's not uncommon for multiple parts to fail around the same time.

When you turn the key to on, 12+V is applied to battery light on the dash, which makes it light up. When you start the engine, a properly functioning alternator ALSO applies 12+V to the dash light bulb...it's like a head-on collision of power along the same wire. If the alternator is working right, the two forces cancel each other out and you end up with roughly 0V at the light bulb, and it goes out. If alternator is weak and puts out say 8V, it's not enough to cancel out the 12V, so you end up with 4V at the light bulb which equals dim/flickering bulb.

Check the battery cable that you just replaced to make sure that it's tight on both ends.

Many thanks - the alternator/battery/starter explanation makes a lot of sense.
I'll check out the cables again, also.

If it comes down to being the alternator and it needs replacing, are there a lot of different varieties or will one Mitsu 4x4 fit all?

It's the alternator failing. You need a 2.6 alternator, starion or monty, starion makes more amps. Getting yours rebuilt is the easiest path here, don't know about there.

I used a Galant 105-amp (??) for a little bit, too.

Cheers, Eddy.

Rebuilds probably available here, but done by a guy sat holding parts on the floor between his feet while he taps away with a hammer.
I'll take a few beers along for a look-see.

Russell, if I remember rightly - you may have spares available. Would you happen to have a known-to-be-good alternator pulled from a 1987ish 4g54 2.6?

Also, is there any possible way - and I mean ANY way, that the alternator can be swapped out without messing with the air conditioning system?

Problem solved.

I ran a new earth strap big enough to jump-start the space shuttle directly from the top fixing bolt of the starter motor to the battery negative post.
Volts are back to 14 on the dash meter, no more battery light on, easy to crank and start when leaving the gas station.

There's a bad earth cable somewhere (maybe more than one) not carrying enough load... bad contact, degraded copper, whatever.

After looking at the alternator reman process here and looking through the electrical FSM, (cheers Monty), I really didn't want to get into stripping out the aircon unit and messing with a "new" alternator.

Lucked out - worth a try if you have the same problem.

Cheers

Rob

OK, scratch that.

The problem was gone, I drove around for 20/30 minutes and went for some gas, came home - no problem at all.

Then I washed the car and put it inside - waited 1 hour at home then took the Mrs shopping, and now the problem is back. 12v at the dash meter and a very dimly lit-up battery light.

The problem started just after a downpour that left the streets flooded to knee depth at max. The car was parked outdoors throughout the storm, and I drove a bunch of kids home after their very wet football match through the floods.

When I washed the car, I didn't use a jet-washer or go under the arches etc - just a small hose from a domestic tap... washed the car from the top down.

Could it be water ingress causing a problem somewhere?

Left the truck indoors at all times at home and parked undercover when out - kept everything dry and the problem went away.
No worries - problem's not been seen for a good couple of months, now.

Somehow, water ingress caused it. Lord knows how and I'm not about to question him... the alternator works now.