Thread: Battery warning light, but charging

Check your earths and clean where necessary.
regrds PhilipA

i just looked at the schematic for the 2.4. there is no stand alone input for the battery light at the cluster so it must be a signal over can bus. i recently had a situation that the +ve lead to alternator had been removed and the nut was finger tight. The terminal was barely touching the post. I watched on my scan gauge the volts drop from low 14's down to 11.8 in a 2 hour drive from home to Goulburn. The battery warning light came on, smack on 12v. Not your problem and not likely offer a solution.

If your scan gauge is reading 13.7 at the same time the warning light is on, there is something amiss between the ECU, CAN Bus cables and the instrument cluster. The scan gauge is reading the volts in the battery/12V system not the output of the alternator (my experience above, there was no charge coming from the alternator because i had no charging cable termination).

I assume your alternator is +/-14.2V under normal driving conditions not 13.7. 13.7 is too low.

FYI - the Puma alternator is a self exciting alternator. The ECU over a LAN wire monitors the output and provides a signal what output to produce.

Alot of antidotes and no solution, sorry.

In a mechanical system the red light is the difference in voltage between the alternator and the battery. bright means big difference dull small difference.

One test you could do to test whether this applies to your system is to connect the negative of the battery to the body of the alternator with a heavy jumper wire like eg starting jumpers. It will not hurt anything.

if you find that the red light goes away, then clean the alternator mount bolts etc as a start and then progress to all the other earths.
If not then you have an electronic problem. Or you may have a crook diode in the alternator, but you say you have replaced it.
Regards PhilipA

Originally Posted by MLD

i just looked at the schematic for the 2.4. there is no stand alone input for the battery light at the cluster so it must be a signal over can bus. i recently had a situation that the +ve lead to alternator had been removed and the nut was finger tight. The terminal was barely touching the post. I watched on my scan gauge the volts drop from low 14's down to 11.8 in a 2 hour drive from home to Goulburn. The battery warning light came on, smack on 12v. Not your problem and not likely offer a solution.

If your scan gauge is reading 13.7 at the same time the warning light is on, there is something amiss between the ECU, CAN Bus cables and the instrument cluster. The scan gauge is reading the volts in the battery/12V system not the output of the alternator (my experience above, there was no charge coming from the alternator because i had no charging cable termination).

I assume your alternator is +/-14.2V under normal driving conditions not 13.7. 13.7 is too low.

FYI - the Puma alternator is a self exciting alternator. The ECU over a LAN wire monitors the output and provides a signal what output to produce.

Alot of antidotes and no solution, sorry.

Thanks for that info. Photo was taken stationary at idle and with the headlights on so happy with 13.7V there. It usually sits at 14.0 to 14.1V.

Originally Posted by PhilipA

In a mechanical system the red light is the difference in voltage between the alternator and the battery. bright means big difference dull small difference.

One test you could do to test whether this applies to your system is to connect the negative of the battery to the body of the alternator with a heavy jumper wire like eg starting jumpers. It will not hurt anything.

if you find that the red light goes away, then clean the alternator mount bolts etc as a start and then progress to all the other earths.
If not then you have an electronic problem. Or you may have a crook diode in the alternator, but you say you have replaced it.
Regards PhilipA

Thanks Philip. The red light is always strong...either on or off. The trick will be to be able to test the alternator for earth when the red light is on, as more often than not everything is fine, but will definitely do this if possible. Cheers

as noted the instrument panel cluster gets its info from the single pair of can bus wires from the ecm to the IP cluster.

*You could pop out the IP cluster and unplug, clean, plug back in the plug on the back.
*Also unplug you digital gauge thing and see what that does.
*on the earth side, you could try, drivers side on the transfer case at the back/top there is an important earth bolted to it, seen plenty of this earth not bolted on the transfer case or loose, it causes some very odd electrical faults, this may be one such example.
*Another earth is passenger side in the engine bay on the firewall near the ecm.

Just as another thought, check the plug on the back of the alternator, i'm pretty sure its to the ecm (engine computer) and back.

Try changing the battery in the key fob.

Originally Posted by DazzaTD5

as noted the instrument panel cluster gets its info from the single pair of can bus wires from the ecm to the IP cluster.

*You could pop out the IP cluster and unplug, clean, plug back in the plug on the back.
*Also unplug you digital gauge thing and see what that does.
*on the earth side, you could try, drivers side on the transfer case at the back/top there is an important earth bolted to it, seen plenty of this earth not bolted on the transfer case or loose, it causes some very odd electrical faults, this may be one such example.
*Another earth is passenger side in the engine bay on the firewall near the ecm.

Just as another thought, check the plug on the back of the alternator, i'm pretty sure its to the ecm (engine computer) and back.

Thanks Daz
I'll check that out. Cheers