In the last two weeks, our car's developed a new problem: about once a week, with no warning, the battery's too low to start the car. My wife (the main driver) has taken long enough trips to recharge the battery from any losses during starting, and drives the car every couple of days or daily. The battery and the charging system test OK (auto parts stores tested them), and I'm not finding any standing voltage drain - it tests at 0.02 amps of standing (everything's off) voltage drain. The top of the battery is good and clean.

What should I be looking at?

Did you check that the glovebox light goes off when closed? Everytime? I pasted a round felt stickum on the lid, the kind that you buy for cabinet doors and/or chair legs.

Find yourself a cheap multimeter, less than $20, and check the voltage at the battery the next time the starter does not engage. You need more than 10V.

Depending on the age, you might need a new battery. The sediment buildup could be messing up one cell which could clear itself with a couple of bumps.

The alternator should be delivering 14.5V at idle with a fully charged battery.

Klaus
--
1967 220 belonging to C.A. lives on

Indeed, it was the glovebox light, intermittently not turning off. When I checked it before (two weeks ago, not a week - time flies), the switch was working; not this morning. Time for a shim on the door.


At the moment, the solution was to remove the bulb.

For what it's worth for other folks tracing this kind of problem, I pulled fuses in groups of five to isolate the group in which the drain was occurring, then replaced them one by one in the problem group to identify the specific set of circuits involved. With the huge number of fuses in the 850 (compared to my 1949 Studebaker truck, which had exactly one), pulling them one by one would have taken a long time.

What do you measure for residual current flow with that light off?
(did you pull a battery cable and measure in series?)

Bill, you seemed to have jumped to a conclusion without demonstrating why you reached that conclusion.

Sounds like your wifes car does not start and you've concluded that the battery is the cause.

Why?

Please describe what happens when the car fails to start.

Does it turn-over at all? Do the dashboard lights come on? Do the headlights look strong?

When it is in this condition, how have you resolved it? Do you put the car on a charger and, the next day, everything is fine?

Please give us some more details.