Charging problems - alternator or voltage regulator or...?

[carrot]

Hi! How do you diagnose a charging problem? I had about 12.1V across the battery when it was running, but it is flat now. The problem seemed to come up quite quickly after a small 4WD'ing trip. So... any suggestions on how I determine what is wrong? Thanks! Oh, it's a GQ petrol BTW.

[midi73]

Hi! How do you diagnose a charging problem? I had about 12.1V across the battery when it was running, but it is flat now. The problem seemed to come up quite quickly after a small 4WD'ing trip. So... any suggestions on how I determine what is wrong? Thanks! Oh, it's a GQ petrol BTW.

If it is only 12.1 when running, it sounds like it is not charging. Did you go through water, on this little 4x4 excursion of yours?

[carrot]

Yeah, it isn't charging, coz now it's flat and needs jump starting. We did go through some shallow rivers and puddles, but they were maybe only up to 20cm deep.

[CWBYUP]

wd40 in the back of the alternator once you get it running again.

worked for mine, otherwise a wire has come off.

isn't 13.6 the minimum you want across the battery at idle ?

Nick

[killalux]

you want around 13.6v, the voltage reg is inside the alt.
WD40 in the back may help but i doubt it if it already dried out. It could make it worse if it mixes with brush dust and causes the brushes to stick.

[bazzle]

Sounds like the brushes are not touching properly.
Hose out alt, see if prob goes away (mud ingress).
Remove alt and check brushes and area for crap worn brushes. If all ok may be diodes, regulator etc

Bazzle

[juls]

Or fuse. Took a little bit to track down this as the cause of my alternator stopping at wonnagatta.

From what we worked out, the trace wire went through the fuse block.

You need a multimeter and wiring diagram to determine if the alternator is charging or if it is a wiring issue.

[stirlsilver]

Would doubt it's a blown diode or a loose winding since there is 3 phases in alternators and at most you will only ever loose one at a time (in which case the alternator still charges but it isn't steady).

Is the alternator externally or internally regulated? Does the charge light come on when you flick the key to the "on" position with the engine off?

Do you have a multimeter? If you take a photo of the alternator showing how it is wired up, we might be able to help diagnose this further by telling you where to look.

[carrot]

Thanks for all the replies! The voltage is regulated internally. I took the alternator out and popped it open, and everything looked ok, so I took it down to an auto elec and they talked me into getting a new one for $260. It's working now! [/i]