[praneshpal]

While driving I lost the RPM indication and lost power. (For a while the radio had been cutting in and out )
I pulled to the side of the road and turned the engine off.

When I tried to start it gave typical low battery with relay clicking. (Battery about 6 months old– usually lasts me 3-4yrs)
I waited 10 min and managed to start again. I drove to work and turned engine off.
Same battery issue – clicking. Can’t start. Waited and the battery recovered.
Started car again - checked voltage at battery - 12.4 V - Revving engine no change in voltage. Lifted the negative off the battery while engine running and the engine stopped.

Car does NOT bring on charge light when key "ON". Also no charge warning light when engine running.

I am presuming fuse to charge light and pre excitation resistor blown so no supply to field coil OR maybe just the light not working.

Will test in the weekend. Some cars have the light in series with the field so if light is blown no supply goes to the field coil. Any one know if Lantra is same?
I don't have the right version electrical diagram ( I have one from Elantra 2001) - so if anyone has it will be appreciated.

Thanks.

ps - car is right hand drive Australian model - not that it matters for the electrical system

 

[Drunken Elvis]

This is a US 1997 Elantra

 

[praneshpal]

Thank you.

 

[AUTOSPARK]

Some cars have the light in series with the field so if light is blown no supply goes to the field coil. Any one know if Lantra is same?

Yes, it is. But the charge warning light is powered by the same source as all the other warning lights on the instrument cluster. So it's not likely to be a blown fuse if the oil light, etc works.

No charge warning light when the ignition is switched on is often because the field circuit inside the alternator is open circuit, usually because the alternator brushes/slip rings are worn. To confirm that is the case what you do is disconnect the 2 wire connector off the back of the alternator and ground the warning light control wire (white/yellow, according to the diagram). With the control wire grounded, switch the ignition on and see if the charge light is illuminated. If it is you know the warning light wiring is good, meaning the open circuit is inside the alternator itself.

If I helped you fix it, why not...

Your support is greatly appreciated​

 

[praneshpal]

Yes, it is. But the charge warning light is powered by the same source as all the other warning lights on the instrument cluster. So it's not likely to be a blown fuse if the oil light, etc works.

No charge warning light when the ignition is switched on is often because the field circuit inside the alternator is open circuit, usually because the alternator brushes/slip rings are worn. To confirm that is the case what you do is disconnect the 2 wire connector off the back of the alternator and ground the warning light control wire (white/yellow, according to the diagram). With the control wire grounded, switch the ignition on and see if the charge light is illuminated. If it is you know the warning light wiring is good, meaning the open circuit is inside the alternator itself.

If I helped you fix it, why not...

Your support is greatly appreciated​

With the control wire grounded, switch the ignition on and see if the charge light is illuminated.

To confirm that is the case what you do is disconnect the 2 wire connector off the back of the alternator and ground the warning light control wire (white/yellow, according to the diagram). With the control wire grounded, switch the ignition on and see if the charge light is illuminated.

To confirm that is the case what you do is disconnect the 2 wire connector off the back of the alternator and ground the warning light control wire (white/yellow, according to the diagram). With the control wire grounded, switch the ignition on and see if the charge light is illuminated

Good idea - what I will do first is rather than grounding it I will disconnect and measure the voltage at the terminal. if the light and fuse are intact I should get battery volts (~ 12V) . That will then isolate the fault to the alternator.
I think you have nailed the problem - it is an internal alternator problem - most likely the brushes.
Thank you for your input. Will post what I find.

Out of curiosity does anyone know why the RPM meter would have gone to zero - I have heard that the low volts will cause the RPM indicator to fail as the low voltage causes the sensor to fail. Does the RPM come from the crank sensor or does it count pulses on the ignition?

 

[praneshpal]

I tested the charging light circuit by earthing the wire that comes from the light. Light worked fine so fault in alternator. Brushes looked ok. Did not check further - will order a new alternator . If new one does not work then must be an earthing issue and the alternator must have been ok. Alternator is $80.00 so not too big a deal . Will post how it went with new alternator.

 

[praneshpal]

New alternator (rebuilt one) put in. All ok.