I have a 1994 E-350 Shuttle Bus. 7.3liter diesel - non-turbo. 200 amp alternator. At idle the voltmeter reads a steady 13v or so. Driving down the road with no electrical loads the voltmeter will pulse between 12v and 14v. If I turn on the A/C the pulsating stops and the voltmeter will read 12v. If I have my headlights on they will pulsate along with all the other light on the bus. I just replaced the voltage regulator because the autozone guy recommended it. All they had was a 100 amp one - is that okay with a 200 amp alternator? It did the pulsating thing before I changed out the voltage regulator also.

Also, The A/C in this bus draws alot of power. If I have it on while idling the voltmeter will start reading 10v after about 5 minutes. Both batteries are brand new. Would a deep cycle for the main battery help at all?

Thanks, Jeff

1994 E-350 Shuttle bus
7.3 liter diesel - non-turbo

 

Sounds like the prob I was having with bothe my trucks, and both times it was the alternator that was causing it, olny diff is that the trucks could have everything on at idle and after about 10 min it would do it as well. Ideally, when you replace the alternator you should also do the regulator so they are both new. But it sounds like the alternator is trying to overcharge the batteries and the regulator is reacting to that.