The fact is many folks run a straight wire. no problem. MAD Electrics and others say no bulb need except for indicator. Go figure. No really...go figure/give your opinion and let the info flow.
I don't do 'opinions' but was curious about this so I did some experimenting with my truck. It is a custom harness and the exciter wire is connected to the ACC side of the fuse panel so it is separate from the ignition hot side. The wire connects to an indicator lamp and the lamp to the alternator. The alternator is a run of the mill 10SI GM alternator, an early one that is not metric. The ammeter always indicates charge immediately when the engine fires.
First I took the bulb out. With an open circuit to the exciter terminal the alternator did not immediately charge. When I increased the rpm to about 3000 it began to charge and continued to operate as normal once it started to charge.
Then I bypassed the bulb with a shunt which would be the same as a straight wire from the ACC side of the switch to the alternator. The alternator began to charge immediately when the engine fired up. When I turned off the ignition the engine died just like normal. I repeated this exercise several times and the engine never ran on after the ignition was turned off, no different than with the indicator lamp in the circuit.
So in my case, having an indicator lamp made no difference. I am keeping the indicator lamp in the circuit, I don't want to risk the run on situation which would likely happen at the most inopportune time.
Your mileage may vary
Mark
