How to test alternator
At low RPM's(idling in drive), my stereo shuts off because it doens't have enough power.
Wait, careful about making an assumption as to the "because", until you've tested and traced a couple more more items. You may be right, but the process of thinking through the diagnosis can easily be tainted if you already think you know what the problem is.
So i'm thinking that I either have a bad battery, or an alternator thats going out.. How do i test the alternator?
A voltmeter will tell you mountains. Attach to cigarette lighter, or any fusebox terminal-- the basic system voltage should be the same no matter where you test. 12.6V indicates a fully charged battery, engine off. With engine running, a functioning alternator should provide at least 13.5, probably 13.8, maybe even low 14s. If the battery has been really run down recently such that the alternator is doing a great job of bringing it back up in a hurry, mid 14s isn't unreasonable.
It's a little hard to imagine that the voltage drop caused by a dome light energizing is enough to trigger audio shut-off circuitry, unless you've been running the battery down below 11V or so... and if so, I suspect you'll find out pretty darn soon when there's not enough juice left to start the car.
- Erik
64 Valiant, 170 3-spd
82 Volvo wagon, 5.0 5-spd :)
