Battery drain issues '84 300D - what is quiescent current drain?
 

Hi all,

My car was getting hard to start as soon as it started raining a lot here in Portland, OR. Then during the heaviest rains, it wouldn't start at all. All the dash lights would fade and the engine wouldn't turn over. A jump start got me going, and I put the battery on a charger all night.

I disconnected the ground terminal from the battery and attached an ammeter in series. It read 25mA. Is that a normal quiescent load for the car when it's off?

I reconnected the battery and started going through fuses that control things that work when the ignition is off. Bada-bing! Fuse #2 (clock, trunk light, diagnostic, switch-over valve seat back arrester [for a coupe?], roof light front + rear, hazard warning system, automatic antenna, illuminated vanity mirror, warning monitor term. 5, electronic radio) gives a load of 25mA.

So if 25mA is not a normal quiescent load for the car through that fuse (like does the clock use that much current?), are any of those others known problem areas?

I did have a problem where I tried to put on the hazard blinkers the other day during the rain storm and there was just a loud buzzing from the switch. I tried it again a few times and it started working again. Also, the bulb in my transmission selector went out.

Thanks!
Aaron

25ma is insignificant. Sounds like the clock all right.

Since there's only 25ma I don't think there's a battery drain at all. Try checking the alternator, also how old is the battery?

The battery is at least 4-5 years old. I remember replacing it around that time.

I believe my alternator was replaced within the past 18-24 months.

Battery voltage is 12.48 when the car is off, 14.08 when the engine is running.

Any thoughts?

What kind of radio is in the car?

I had similar situation and it turned out to be the battery but something like alternator diodes could cause intermittent charging. Measure battery voltage with cables disconnected. Also, put 1 lead in cell 1 the other in cell 2. Note voltage. Move lead from cell 2 to cell 3. Note voltage each time. It should increase 1/6 with each cell. Repeat after battery sits over night. You could also load test battery by connecting volt meter & cranking engine. Also take to idiot at the chain parts store & have them test charging system and battery.

Had a similar problem in my 300SD. Turned out to be the power antenna.

Sincerely,
Brian

This is one of my biggest pet peeves with these cars. Putting a bunch of accessories on one fuse is probably the dumbest thing I have ever seen.

I kept blowing fuse 2 when I pulled my car out of storage. It ended up being the power antenna, but it honestly can be any one of those accessories.