Can’t find the thread that has the diagram I used. I wired the LED in parallel with the incandescent bulb and this worked good for 5 months/300 miles but now the LED stays on. Key on and both lights are on. Engine running only the LED is on. The LED started out flickering when I was going down hill then it would be on for a bit now and then and still flicker down hill and now it’s just on all the time. 12v conversion with a 10si alternator. Tested at the battery and alternator 12.6v running or not it’s the same. Took the + cable off the battery while running and it stayed running and output stayed at 12.6v.
12.6 is too low when running and also don't unhook the battery while it's running, it could damage the alt. Best is to check the charging amps also if you can. https://www.jalopyjournal.com/forum/threads/alternator-idiot-light-will-led-work.1183762/ Why did you have a led AND an incandescent bulb.
LEDs or simple diodes can short out and pass current Isolate it from the circuit and do a continuity check both ways.
An LED has a limiting resistor in series with it, otherwise it is basically a short circuit which will glow very brightly for a second and then let the smoke out. As said above, disconnect one side of the LED, and you should have a normal 2w "gen light" circuit. If this works OK, replace the LED (make sure it has it's limiting resistor- about 470 ohms for a 12v system.)
so when I wired this last year I followed a thread on here where it said to wire the LED in parallel with the bulb so that’s why I have it like that and it worked until this weekend. Ivan follow a wiring diagram but that’s my limit of understanding of electrical. I am ready to ditch the LED.
Maybe a ground loop. The light stays off because you have 12v either side of the bulb. But the 12v comes from different directions in the harness. Any miniscule volt drop on one side or a different potential at an earth point would be enough to light an LED but not a bulb. It could just be down to connector resistance changing over time.
Yes it could. Does the voltage go up if you increase rpm to say 1500 rpm? If the battery is good and all accessories are turned off, you should see around 14.5 at 1500 rpm. If not, there is a problem with the alternator or voltage regulator (inside the alternator). Also, removing the battery cable with the engine running is hard on the alternator and the whole electrical system. The battery is what controls the output voltage the voltage regulator is looking at battery voltage to control alternator output. Without it in the circuit you could see 40+ volts.
No increase in alternator output at higher rpm and no increase when I took the + cable off the battery while running. Tonight I will take the exciter wire off the alternator and run a wire with a light from the battery to the exciter terminal. If the alternator works then I can assume it’s the LED or the way it’s wired causing the problem. If there is no change then I can assume it’s the alternator. Am I on the right track?
So I tested it tonight. Took off the exciter wire from the harness and ran a wire from the battery to the exciter terminal with a 5w light inline. Had 11.5v at the battery not running. Had 11.5 at the alternator running and the light was red/dim but still on. So I guess it’s the alternator.
Removing the battery cable while running should make the alternator peak out (and hurt it) so if it didn't change that explains why your LED light stays on. It's telling you the alternator is bad.
Only had that reman alternator 4 months. Did a warranty return at oreallys and and got another Wilson reman and it’s working and charging and the light is off.
The Jalopy Journal
