23-10-2015, 03:44 PM
(23-10-2015, 08:46 AM)ex 2 Base Wrote: The "Dummy light " or" idiot light" is the ignition warning light on a car. We had a car and the bulb was loose in it mounting which then stopped the alternator from charging. We were going home and the engine stopped for no apparent reason. When I tried to start the engine the battery was completely flat, no ignition warning light of course. Fortunately for us a neighbour saw us and stopped, he had a strong rope in his boot and gave us a tow home, just about a mile. After charging the battery the engine started, no ignition warning light , I checked the alternator, no output . I was a bit confused and then started to check the rest of the charging circuit and it was then I discovered the loose bulb. What a job to remove the dash to gain access to a simple bulb. The manual said you had to remove the steering wheel, with all that entailed. I managed without removing the steering wheel as so many controls are mounted on the steering wheel.It excites the magnetic field. I was a bit frustrated over explanations of dummy lights online but someone on a racing car forum cleared it up.
Finally I've done a few jobs on my friend boats and notice all their alternator are battery sensed. Ted
You'll find the D+ wire on the back of the alternator and it's thinner. That will cause the bulb to light but it should become positive on engine start and the bulb will go out. That's why they say 12 volts each side but really it's just zero potential between 2 terminals that are both 12 volts positive between each one and chassis.
