LFA

1991 GT; alternator is not charging the battery, alternator is working but looks like the light in the instrument cluster is not enough to trigger the alternator. Is there an additional resistor somewhere?
Thanks for your help.

WallyP

We need a bit more info...

How do you know the alternator is working, but not charging the battery?
When is the alternator warning light on? Off? What is the voltage at the battery with the engine not running? With it running?

First thing to check is the belt - it should be very tight.

Second thing to check is the connection thru the fourteen-pin connector near the jump start terminal - it is not unusual for there to be high resistance here.

GregBBRD

Even without a light bulb or a resistor, the alternator will charge (if it actually functional), if you rev the engine above 4,000 rpms. The early cars had a resistor actually attached with screws to the circuit board for the instrument cluster. It was put there as a back-up to the light bulb. If the light bulb burned out, this resistor still allowed the alternator to charge. There may still be such a resistor on a the digital dash cars, but I have no idea where it would be.

Have you added an additional light bulb into the circuit to test your theory?

That would be simple to do at the 14 pin connector....

Jetdriver69

My 82 5 speed with aftermarket 180 alternator won't excite unless I rev it slightly (1800 rpm). But I have a very small pulley spinning the alt faster than normal.

My alt light is burnt out but it will excite as Greg said. However I have noticed that now it is colder the alternator will excite on start up.

If I pull the pod to change the bulbs to LED and adjust the voltmeter, I will change the light assembly.

Alan

How do you know the bulb is burned out...? any open circuit on the way to the alternator will mean the bulb won't light.

Try grounding central electric pin O8 with ignition on - if the (no) charge bulb doesn't light it is likely burned out (or not connecting), if it does light you have a connection problem downstream. The bulbs rarely burn out - they aren't on very much and they are never at full voltage.

Alan

Jetdriver69

I did that a while back per your advise and no light.

So I am assuming the light is out. All other electrics work as advertised after CE panel refresh, ground cleanings, new negative strap, etc.

Steady 13.8 on the voltmeter and on the post, 12.8 or so on the post after shutdown.

Mostly just an annoyance...