I used sealed LED indicators on my new engine panel for alternator, oil and temp warning.
When I fired up the engine for the first time, the alternator didn't work. After a bit of research, it turns out the filament bulb is what passes the initial excitation current to the alternator. Once excited, the alternator is self sustaining.
Long story short, a 47 ohm (hot bulb equivalent) resistor across the LED unit solves the problem. Alternator works and the LED still lights before the engine starts and if I remove the drive belt.
Also, for those with filament bulbs, if the alternator light burns out the alternator will not charge. Didn't know that before...
Another guy I talked to knows of a few people who had their alternators replaced when it was just the bulb burned out.
I've read that not all alternators work this way. Most now are self exciting and designed to drive any form of indicator lamp.
Learn something every day....
Chris
When I fired up the engine for the first time, the alternator didn't work. After a bit of research, it turns out the filament bulb is what passes the initial excitation current to the alternator. Once excited, the alternator is self sustaining.
Long story short, a 47 ohm (hot bulb equivalent) resistor across the LED unit solves the problem. Alternator works and the LED still lights before the engine starts and if I remove the drive belt.
Also, for those with filament bulbs, if the alternator light burns out the alternator will not charge. Didn't know that before...
Another guy I talked to knows of a few people who had their alternators replaced when it was just the bulb burned out.
I've read that not all alternators work this way. Most now are self exciting and designed to drive any form of indicator lamp.
Learn something every day....
Chris