Alternator Charging System Question

[Ronnie's.930]

1987 930

Several months ago system was producing only 12.2 volts at about 1200 RPM plus. I ordered a new voltage regulator and since, read 13.6 at the battery with car warm (around 1100-1200 RPM). This is a good number, but when I turn all the lights on the engine idle drops about 100-200 RPM and my voltage reading drops to 13.1. Is this typical? I don't remember this "drop" happening before but maybe I just didn't notice?

I'm also newly using one of those tiny PC680 Odeyssey batteries and am wondering if that could be a problem - need to test with another battery.

Thoughts?

[Porboynz]

Sounds about right to me, your idle speed must be high enough to generate some output but not enough to fully compensate for the load introduced by the headlamps. That's enough load to slow your idle, later model engine ECU's increase the idle speed to compensate for additional alternator loads and air con switch on etc.

[Joe Bob]

Anything over 13 at idle is OK.....13.5 -14 at 2500 is optimal.

[Ronnie's.930]

Thanks for the info.