Outer Limits 4x4 Board

Does it sound like the alternator??
Multimeter on the battery, 12.8v engine off. 13.8v at idle, turn on headlights and highbeam and voltage slowly (in about 30 seconds) drop to 12.5 or less and eventually the radio turns off with it's low voltage protection??

The 12.8V is probably not a true indication of battery voltage off charge. It can take hours to drop and stabilise.

I think the fault is in your alternator or regulator. Residual field is enough to generate 13.8V, but field current isn't increasing to maintain voltage with increasing load. Problem in the field circuit or regulator.

That's my guess but I'd have to take it to an auto sparky from there.

Good luck,

Scott

Turn on the headlights and tell us what the voltage across the battery is...

The voltage at rest you were measuring is consistant with what you would expect with zero load attatched to it. DVM draw almost no current and can give misleading readings in cases like this.

It does sound like a charging issue.

Hi phippsy, DAMKIA’s suggestion will give you some idea of whether the battery is holding a charge but you didn’t say if you revved the motor while you had the headlights on.

If the battery has a shorted cell and you turn the headlights on, the combined current of the headlights and what ever is being pulled by the battery, maybe to high for what the alternator can turn out at idle speed and this can cause the voltage to drop.

Still, the suggestion of having an auto electrician look at it might be the way to go if you can’t pin point the specific problem.

With the headlights on was at idle. I'm pretty confident that it's not the battery as it's only a couple of months old.
DAMKIA, with the car at idle it was at 13.8v, headlights on it dropped pretty quickly to about 12.5v ish.
But also on the way home today all was good until I braked and used the indicator, dropped the voltage and the radio turned off (low voltage protection) also turned radio off if headlights on, or compressor on or combination of the above.

I'm inclined to pull the alternator out to get an auto leccy to look at it, cause I can't afford the $$$ for their labour to remove and install. Or is it better for them to test it on the vehicle? It's a bit dodgy to drive atm with electronics doing weird things.

Iif you pull it out they more than likely will want to pull it down and rebuild it as they will be limited in thier testing ability, and opening it up will probably give them better information anyway.

If you let them have a look at it on vehicle, you can always drive home pull it out and drop it in.

Does the hilux alternator have an integrated regulator?

Yeah, according to the gregory's book it has an internal regulator.

There's an auto leccy we send our trucks to and he seems like a decent bloke so I'll go and have a yarn to him today. See what he thinks.

thanks for the help.