[ZekenSpider]

Originally Posted by Keith Wire

Jerry,

I realize that alternators don't exhibit the same problems that the old generators used to (ie @ idle RPM they almost generated so little it wouldn't charge a battery). But, there is still a difference from idle to say 2000 RPM...

So the question is, what RPM was the Suburban running at?

Keith

As I recall the tach said 800 but it would move up to 1000 when the AC compressor cycled. The important thing for the test was the Suburban battery voltage stayed steady at 13.73 (if my DVM is accurate) regardless of the RPM.

We had just finished a 2 hour daytime drive so the battery was topped off and the voltage regulator had cranked the alternator output down to it's minimum.

I just looked at the Suburban again and right after start-up the RPM is 1,100 to 1,200 and the battery voltage went up to 14.3 for a few minutes then dropped to 13.8. Within 5 min. the RPM dropped to 800 and the voltage remained at 13.8. My testing in the previous post was done over a 15 min. period with the TV battery voltage at a steady 13.73.

Jerry