Battery/Alternator light stays on when ignition is off and key out, RT132 Corona.

[TTMX83]

Basically I was driving home last night and the electricity started to run out, eventually I had to pull over as the battery was dead flat. When I turned the car off to lock it up I noticed the CHG light stayed lit on the dash. When the key is turned to ignition the light does not illuminate, nor does it when the car is running.

This is in an RT132 Corona.

I have Googled for the last hour and not a lot comes up. Some suggestions were the diodes have burnt out, the key barrel is faulty or some dodgy wiring.

Armed with my multimeter, what voltages should be present at each terminal on the battery and alternator with the car running and with it off?

Something to note also is the car started to make a whirring, bearing sort of noise at idle in the last two days. I originally thought it could be the water pump bearing but now I think it is something to do with the alternator. Car is 100% standard as it came from the factory in 1980.

Had a quick look at it now. Pulling the charge fuse out turns the light off. I noticed when reconnecting the battery, it is pulling the voltage regulator relay on (or off) it makes a clicking noise that I can't recall it ever made before.

Many thanks.

Cheers Brad.

[lexsmaz]

Hi Brad,

From your description it sounds like as you mentioned that the Alternator diodes have failed .. If it was a faulty ignition switch it should be powering up other things in the car when you turn the key off, which i pressume its not & also the light Not coming on when you turn the key on sounds like the alternator diodes fautly too ..

Try pulling off one of the small wires off at a time off the back of the alternator with the ignition off & see which wire takes the light off, ( obviously the main battery wire will have power to it so leave that alone ) the wire that takes the light off is the charge light wire & should not be powered up from the alternator with the car off, so once you have found the wire double check with a test light to see if it has power coming out of the alternator on that wire as it normally shouldn't & if thats the case that it has power in my opinion the Alternator is at fault ...

Rob ..

[Dazza]

I would say it is diodes in the alternator that have failed. The whirring noise it is making is a hint.

[TTMX83]

Thanks heaps guys, Bought a new alternator and it's all fixed. Although the new alternator is ever so slightly different in that the adjusting nut is further around so the arm is too short! Modified that and it will do until I can make a proper arm.

Cheers Brad.