arnosub Posted November 21, 2023 Report Share Posted November 21, 2023 Hi, Since I removed the original subaru wrx dash (2002), I no longer have a charge for my battery. I wanted to replace the original light with an LED light but this one stays on all the time and my battery remains at 12.8V. When I reconnect the original dash, the charging light goes out and the battery charges at 14.2V. So there is a link with the dash and I probably have to modify my wiring but I don't see what I should do. Below the original diagram, there seems to be a resistor + a diode above the LED indicator. to give more detail, I currently only have one LED between the + and terminal B1 DenisAlmos 1 Quote Link to comment Share on other sites More sharing options...
Adamw Posted November 21, 2023 Report Share Posted November 21, 2023 Many alternators need significant current flowing through the lamp circuit, into the alternator to excite the field. The factory dash possibly has a parallel resistor across the LED or some type of high-draw LED to achieve this. Your LED, if it was designed to work at 12V will likely have some current limiting resistor in series built-in making it even less likely to work. I would try adding something like a 100ohm, 5W resistor (note these are relatively big) across the LED like below. arnosub 1 Quote Link to comment Share on other sites More sharing options...
KennyJ Posted November 22, 2023 Report Share Posted November 22, 2023 as adam states above , i do this with rally subaru's all the time. i go from B+ bolt to L , i dont add a lamp as you can set low voltage triggers on aim display on system voltage NOTE: i go from B+ to L as these cars have circuit breakers , it would drain the battery on normal cars who keep feeding tje alternator B+ Quote Link to comment Share on other sites More sharing options...
arnosub Posted November 22, 2023 Author Report Share Posted November 22, 2023 thanks all actually, I replaced my LED with a 100ohm resistor and the voltage is 14.2V. It's a 1/4W resistor, could this be suitable? On the other hand, KennyJ, I don't see where the shift between B+ and L is located?Is this the part that I circled in blue? Quote Link to comment Share on other sites More sharing options...
dx4picco Posted November 22, 2023 Report Share Posted November 22, 2023 U=RxI, dissipated power is UxI, so you get around 2W for 14V continuous. that 0.5W in't going to last. arnosub 1 Quote Link to comment Share on other sites More sharing options...
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