Do we have any electrical system guru’s on here?

[Morris]

On a charge light on the dash.....one side goes to the battery via the ignition switch (12 volts) which is 12 volts.....the other side of the lamp .....goes to the alternator which is close to the same on both sides of the lamp putting out 13.5-14.5 volts....which means the lamp will not light because the potential is the same on both sides of the lamp......if the voltage from the battery or the alternator starts to fail....then the difference in potential gets larger and the lamp starts to light.....the brightness of the light depends on the amount of voltage difference between the two sides of the lamp.....it at least warns you that something is not working properly in your electrical supply system....I doubt that the fuel pump had any effect on the Battery/Alternator lamp or supply.

[767Jockey]

Originally Posted by Morris

On a charge light on the dash.....one side goes to the battery via the ignition switch (12 volts) which is 12 volts.....the other side of the lamp .....goes to the alternator which is close to the same on both sides of the lamp putting out 13.5-14.5 volts....which means the lamp will not light because the potential is the same on both sides of the lamp......if the voltage from the battery or the alternator starts to fail....then the difference in potential gets larger and the lamp starts to light.....the brightness of the light depends on the amount of voltage difference between the two sides of the lamp.....it at least warns you that something is not working properly in your electrical supply system....I doubt that the fuel pump had any effect on the Battery/Alternator lamp or supply.

Morris, this darned thing stayed on all the time.

[patrickt]

Originally Posted by 767Jockey

Morris, this darned thing stayed on all the time.

I think Morris confused you. A charging system that actually uses the idiot light does so by running current through the filament of the bulb to the voltage regulator. When it does this, it "excites" the VR to begin charging the system (assuming the alternator is working). The lead from the VR to the bulb is a ground circuit before the exciting takes place. Once the exciting takes place, it is a positive feed. So, when everything is running properly the bulb has a positive feed to both sides of it, so it doesn't light. BUT, if either side is noticeably "less positive" than the other, then the light will burn dimly. If either side is really negative, then the bulb will burn brightly. Sometimes the filament of the bulb does not have the proper resistance so you add a resistor in parallel. Now, here's your quiz in order to get an honorary Club Cobra EE degree: How do you measure the resistance of a bulb's filament when it always shows zero ohms when you measure it with your VOM?

[Dominik]

I am also pretty certain that you cannot use a LED pilot light for above reasons. The resistance would be too low.

[strictlypersonl]

Originally Posted by Dominik

I am also pretty certain that you cannot use a LED pilot light for above reasons. The resistance would be too low.

I think you mean "high"...

[spdbrake]

I switched all my dash lights to LED last year.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
Red=alt, Blue=hi-beam,Amber=Fan,Green=Turn
I used the 24vdc version as I don't like blindingly bright caution lights. These can easily be seen during the daytime as well.

Had to add a Resistor as the LED did not have enough resistance to trip the alternator on and also turn off the light.
https://www.amazon.com/s?k=Twidec%2F...f=nb_sb_noss_2

Back to the OP original question. The alternator may have set too long causing the original problem. https://www.engineersedge.com/motors...d_flashing.htm

[krausewich]

Originally Posted by Morris

On a charge light on the dash.....one side goes to the battery via the ignition switch (12 volts) which is 12 volts.....the other side of the lamp .....goes to the alternator which is close to the same on both sides of the lamp putting out 13.5-14.5 volts....which means the lamp will not light because the potential is the same on both sides of the lamp......if the voltage from the battery or the alternator starts to fail....then the difference in potential gets larger and the lamp starts to light.....the brightness of the light depends on the amount of voltage difference between the two sides of the lamp.....it at least warns you that something is not working properly in your electrical supply system....I doubt that the fuel pump had any effect on the Battery/Alternator lamp or supply.

Morris.. So your saying there is some truth to when the Ol' lady says "I thought the light would get brighter if it were serious?!"

I will never admit to this...

[Blas]

The red light on the dash should turn on with the ignition key in the on position. Once the motor is running and the key is back in the on position (from the crank position), assuming the engines idle RPM’s are sufficient, the red light should go out. There are a trio of diodes inside the alternator. Your alternator is making AC current, and it is being converted to DC current. If any of the diodes are damaged or are beginning to fail, the red light will begin to glow a bit, and as the diode(s) continue to fail, the red light will get brighter and brighter. Most single wire alternators are not designed to have the charging light functional. There are a few exceptions out there and there is an aftermarket circuit that can be added which will make the red light functional again with a single wire alternator. Lots of people put way too high output alternators in cars with wiring not designed for large amperage units.
Blas