More charging questions

[MadRiver]

Ok, eletrical cognoscenti, here's another charging issue. I was puttering around town in the 250 today, and I noticed that my ammeter was always at a slight disgarge when sitting and idling, with none of the auxiliary stuff (heater, lights, etc.) running. If I started driving, the needle went to the midpoint between dead center and the "C" marking. I did a little poking and prodding, and here is what I found. Before starting the car, I tested the battery with my multi-meter, and got a reading around 12.4. When the car was turning over about 3000 rpms, I was getting about 13.6 across the battery terminals. I haven't yet tested the voltage at the terminals at idle (about 800 rpms), but I'm going to do that now.

Any thoughts from the collective? Thanks as always!

B.

 

[TR3driver]

That's fairly normal for a Lucas alternator. They simply don't have much output at idle.

There are some faults that can reduce output even farther, so it might be worth having it checked, but my guess is that it's working "as original". A simple (but crude) test is to turn on the headlights and heater, then rev the engine to around 2000 rpm and see if the alternator can still move the ammeter to charge. If so, it's probably fine.

 

[RobT]

That's normal. The alltinator needs to be spinning above a certian speed (above idle) before it starts to charge. I find between 1,500 - 2,000 RPM before the altinator kicks in. The voltage should be in the 13.5 - 14.5 range.

Rob.