Upgraded Coil, now Alternator Light on Options

[Tastyplacement]

914world, please save me again from my mediocrity.

2316cc T4. I used to have an Empi distributor with Bosch blue coil. I upgraded to pertronix 45kv 0.3 ohm coil and pertronix distributor. Great spark now, easier starts, but my alt. light stays on. Previously, i would have to get rpm over 2500 to make light go off, now no spike in rpm will make the light go off.

I have led bulbs in dash, and i am willing to do the 100 ohm resistor mod to the alt light if that is necessary.

[pbanders]

BTW, because the current through the alternator light depends only on the difference between the voltage developed by the alternator/voltage regulator (call this Va) and that of the battery (Vb), it can diagnose both overcharging (Va >> Vb) and undercharging (Va << Vb). That's because an incandescent bulb doesn't care which way the current is flowing through it to glow.

Not so for an LED bulb, even if you're shorting it with a resistor. It's a diode, and will be forward biased (light-producing) only in one current direction. It also has a turn-on voltage (Vf) that 's determined by the type of semiconductor that's used, which in the case of a white LED is 3.4 V. This means that depending on how the LED is connected, it won't be able to detect either overcharging or undercharging, and because the Vf is 3.4 V, you won't be able to detect marginal charging system problems that would cause an incandescent bulb to glow dimly.

Get rid of LED alternator bulbs! Not a good idea.

[Tastyplacement]

Checking everything--previous owner had mixed up DF and D+. Unbelievable. I don't know by what miracle this car even drove. I keep it on a charger when in garage, so that probably masked any lack of charging.

Light works perfectly now: ignition on, light is nice and bright, goes out completely at about 1100 rpm and stays off.

Get rid of LED alternator bulbs! Not a good idea.

[pbanders]

Checking everything--previous owner had mixed up DF and D+. Unbelievable. I don't know by what miracle this car even drove. I keep it on a charger when in garage, so that probably masked any lack of charging.

Light works perfectly now: ignition on, light is nice and bright, goes out completely at about 1100 rpm and stays off.

Get rid of LED alternator bulbs! Not a good idea.

Wow, like you say, with Df and D+ interchanged, who knows how it ever worked at all. Glad you got it sorted out.