I said I would update; my problem seemed to be the battery!

I had the very nice platinum tested over two days at advance auto and they did return and exchange it for me.

The brand new battery has performed perfectly since installing. No doubt my weak charging system and bad/weak grounds and long periods of sitting contributed to the loss of that one. Oh yea I did also replace the clamp for the positive lead.

Anyway if it comes back again I'll update, I haven't let it sit for more than a couple of days but I believe it was the battery.

What about you OP?? Find the "leak"?

As a follow-up on the resolution of the problem, I had the battery tested several times and it tested fine. It was a one year old Bosch. I finally gave up and bought a new battery. Problem solved.

Richard

The modern car battery in general only seems to last well when in pretty much constant service unfortunately. Or that has pretty much been my experience.

They also seem to have their overall life expectancy reduced when drained down too far. For example if you purchased a new battery and over the period of say the first year. It was totally drained down pretty flat say six times. I would expect a much shorter life than if it had not been. I have no proof of this other than what I think I have observed.

It may be my harsh cooler climate here yet in some ways batteries in hotter climates sufferer their own types of stress.

I devised a glow relay modification (you solder one resistor across two points inside the glow plug relay - documented on this forum - search) that gives this extra indication - but it shows on the normal glow light on the dash you don't have to add an extra bulb. And no extra wiring or wiring modifications anywhere. Only one resistor inside the relay.

The glow light will initially be full bright while starting an active glow then goes to half-bright when the glowing timer is over, and finally goes dark after you start the car. If ever you see any level of brightness while driving, or bulb never goes completely off after starting the car, you'll know plugs are still being energized which of course is a drain on your battery / charging system and burns out plugs prematurely.

__________________
Cheers!
Scott McPhee

1987 300D

At the battery when car is off, and everything switched off, disconnect negative terminal and put an Amp meter in-line to complete the circuit. There could be a surge for about 30 seconds as various devices in the car (alarm system, electric vacuum pump, etc.) do their boot up / power up sequences.... then the car settles down should draw (Rule of thumb) about no more than 50 mA.

If you're seeing 250 mA or more... your battery, even a good battery, will drain in about a week of sitting there if the car is not started. (Quicker drain proportional to amount being drawn of course). If you drive the car every day.. this would never be an issue... but after parking at the airport, say, and returning from the trip... dead battery.

Until you find the problem - you could compensate with a trickle charger / battery maintainer while parked for long durations. But then you're trusting the plug-in to remain good while you're away.

I like the idea of hunting down the high current consumer by methodically pulling fuses and re-inserts while watching your meter on the battery. If NO FUSE pull alleviates the high current (>250mA) draw... well, then you have a potential wiring issue between battery and fuse blocks.. or maybe you added a circuit upstream of the fuse block and didn't put your own fuse on the line?

__________________
Cheers!
Scott McPhee

1987 300D

I am not sure what the three previous answers are addressing. I bought a new battery and the problem was gone. The previous battery was bad.

Richard