Alternator struggling

[taslucas]

I have noticed in the last few days that upon start up my voltmeter is only reading about 10 volts. I can sit there idling for a while and it doesnt move off 10 volts regardles of the engine rpm. As soon as i put it into drive and start moving, the voltmeter jumps up to the normal 14 volts and will stay there wether driving or idling until i turn the car off. The belts are all tight. The voltmeter has always been on 14 volts consistently since i got the trol until just recently.
I do have a noisy bearing in one of the pulleys but that has been there for well over a month where as the volt issue has just happened in the last few days.
What could be going on there? Is my alternator on the way out? Does it just need a clean out?

[Bigrig]

Test the battery charge itself mate, and the alternator also. I wouldn't be relying on the internal gauge for an accurate assessment of what's going on - they're well known for starting to play up.

If you're not getting charge, then yep, you could be up for a new alternator (and battery maybe if it's stuffed from being drained etc).

[taslucas]

Cheers,
Battery is good. So do I just test the alternator with a multi meter while running? It should read somewhere around 14 volts?

Tap, crackle, pop

[Winnie]

Yep that's right. 13.5V-14.5V should be around what you want.

[Sir Roofy]

With what you do with your troll mate and looking back on
a pic you put up of your motor covered in mud id
suggest an overhaul of the alternator is due

[patch697]

Cheers,
Battery is good. So do I just test the alternator with a multi meter while running? It should read somewhere around 14 volts?

Tap, crackle, pop


Yep test for charge at the + pole (heavy white wire from memory) with the engine running but keep the revs up while testing to get an accurate reading, as some alts don't charge well at idle like Bosch for example & need a few revs to get there charge rate up.

[threedogs]

Heres what happened to mine, no warning, no noise, temp soared then Patrol stopped, that was is FEB still sorting all the gremlins associated with it. Changed every sensor on it
If yours is birdcage style would say its US and needs bearings and brushes put through it, cheaper than a reco.
They need the revs up a bit to excite them to start charging,

[Yendor]

It could possible be a weak diode or even the brushes getting low in the alternator.

Possible even a bad connection in the alternator sense circuit.

The first thing I would check is your earths and the connections at the back of the alternator.

Then check the sense circuit, in the small plug that connects to the alternator there is a white wire. Connect a test light to this white wire it should light up.

While watching the test light wiggle the harness up to about six inches away from the alternator, does the test light flicker or go out?

If the above is ok, then start the engine and compare the voltage readings across the alternator and across the battery at a fast idle.

It will also be a good idea to perform this check with some load on the alternator so turn on your high beam and interior fan.

[taslucas]

With what you do with your troll mate and looking back on
a pic you put up of your motor covered in mud id
suggest an overhaul of the alternator is due

Quite possibly. Ill say it again though: cant drive out your driveway without hitting mud here:)


Yep test for charge at the + pole (heavy white wire from memory) with the engine running but keep the revs up while testing to get an accurate reading, as some alts don't charge well at idle like Bosch for example & need a few revs to get there charge rate up.

I called in to an auto eleccy this arvo and he said it would be fine to test it at the battery to see if the alternator was putting out a good voltage?


Heres what happened to mine, no warning, no noise, temp soared then Patrol stopped, that was is FEB still sorting all the gremlins associated with it. Changed every sensor on it
If yours is birdcage style would say its US and needs bearings and brushes put through it, cheaper than a reco.
They need the revs up a bit to excite them to start charging,

Was that a siezed bearing?


It could possible be a weak diode or even the brushes getting low in the alternator.

Possible even a bad connection in the alternator sense circuit.

The first thing I would check is your earths and the connections at the back of the alternator.

Then check the sense circuit, in the small plug that connects to the alternator there is a white wire. Connect a test light to this white wire it should light up.

While watching the test light wiggle the harness up to about six inches away from the alternator, does the test light flicker or go out?

If the above is ok, then start the engine and compare the voltage readings across the alternator and across the battery at a fast idle.

It will also be a good idea to perform this check with some load on the alternator so turn on your high beam and interior fan.

Awesome reply Rodney, thanks mate. I will try to check those things this weekend. This morning i noticed that the battery light on the dash was lit up ever so faintly while the gauge was showing the 10vlots at idle. So im guessing that rules out a faulty guage? This arvo when i started it after work the gauge went straight to 13.5/14 (and no battery light at all). Also i noticed my lights flicker ever so slightly a few times on the way home- not sure if that has anything to do with anything (except mud lol)

Thanks for the replies guys:)

[threedogs]

Had a slight squeak at camp at idle, could hardly here it, disappeared with the revs raised slightly. thought it was only water on the belts.
Only got about 80ks home everything stopped, seized the bearing in the clutch on alternator, would never have picked the noise as bearing
and would never have made it home no matter what we did, other 4x4 towed my camper. RACV towed the GU for free, total fix to get mobile $370

[taslucas]

Bugger. Mines squealing pretty bad but im not sure which pulley/bearing it is yet

[kiwijase]

shouldnt you "Load test" the battery?
It may be losing cranking amps but show a standard volt rate while idling? I had same problem you describe,thanks to Rodney Its sorted.
I went and bought new batterys and a new alternator.....now just hubs and bearings to do.