I'm looking for help finding the cause(s) of the battery draining on our 1983 300CD-T (Calif.) and would appreciate any ideas or suggestions.

This problem has been present for probably five years (or perhaps longer) - I'm getting old and memory ain't what it used to be!
Current mileage on the vehicle is about 247,000.

Symptoms:
Every three to four months, I'll get in the car and try to start it and upon turning the key to the pre-glow position, the instrument cluster lamps are all off and of course, the starter won't turn (like this morning). I can usually jump start the car.

Background:
1. Every other week, I drive the car to and from work, Monday through Friday (roundtrip is about 26 mi.). On the "off" week, the wife drives it around town on two or three days.

2. Battery replacements:
2001: 228,600 mi.
2002: 231,800 mi.
2004: 240,800 mi.
2006: 242,400 mi.
2008: 244,900 mi.

3. When I start the car (when the battery has sufficient charge), it starts and idles just fine. HOWEVER, while idling, the battery light in the instrument cluster glows bright red. If I never press the accelerator pedal and just sit there and idle, the light remains on no matter what. This seems like a clue that something is wrong. All I have to do is to rev the engine once, the light goes out, and never comes back on.

4. The last time the alternator was replaced was in 2001 at 229,800 mi. At that time, it was replaced with a Bosch rebuild. About six months ago, I had the alternator tested at a local auto parts store and it tested as ok.

5. I disconnected the antenna a year or so ago and that did not appear to affect the problem.

6. I have confirmed that the trunk lamp is not on when the trunk is closed.

7. I have confirmed that the courtesy lamps (front and rear) are not on when the doors are shut and the devices are turned off.

8. I have confirmed that the ground strap near the transmission is securely fastened.

9. I have confirmed that the ground wire by the antenna in the trunk is securely fastened.

10. Headlights, taillights, turn signals, wipers, horn, fuel gauge, power windows, emergency flashers, radio, power outside rearview mirror, glove box light, fog lights, climate control/fan, instrument cluster lamps, tachometer, and defroster: none appears to be on when it shouldn't be and all appear to work properly.

11. The cruise control doesn't work (I don't think, it has been a while) and neither does the power sunroof.

12. Clock in instrument cluster keeps accurate time.

13. The vehicle is stored in my garage in Phoenix, Arizona.

Any ideas for methods to track down the problem(s)? Special tool(s) to use?

Thanks-

__________________
Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

What kind of radio does your car have?

__________________
1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg

when you connect the battery does it arc?

__________________
have no worries.....President Obama swears "If you like your gun, you can keep it

not sure what the issue is, but you might consider a battery disconnect under the hood, since you don't use it that much.

when you do drive it, are they short little trips or longer trips including highway time?

__________________
1985 300D cali 190K

http://mercedes.thatchermathias.com/mw300d.jpg

Pull the fuses 1 x1 until the drain goes away

Do an amp draw test then report back.

X2 on aftermarket radio

__________________
1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)

Have you checked the starter? You don't mention if on the occasions when it won't start whether the other electrics work well or not. The signs (especially #3) would point to a charging problem, but you might have a bad starter that needs some extra "oomph" to engage. When it won't start do you get a "click click" of a closing relay or a slow "rrr rrr" of a weak battery?

Also, when you say "pre-glow" position with no lights, are you referring to position I? If so, mine operates the same way. Position I is sort of like the "accessory" position - the radio works, some other stuff, too, but no dash lights. Rotating further I get the dash lights and glow plug.

Are you certain you have the correct size battery in the car?

If so, then as Oracle suggests, you might be able to use an ammeter (digital multi-meter set up for measuring current) and go through your fuse box one by one to find where the largest draws are.

Basics would be to remove the fuse, then measure the current going across the circuit using probes, then repeat. Since the major symptom appears to only show every few months this might not show up clearly. And you need to be careful poking probes into your fuse box.

Does background # 3 - the battery light - ALWAYS behave this way, with every start showing an insufficient charge?

Does background # 5, the antenna refer to the original factory antenna or an aftermarket? Is it still disconnected, or was that a temporary troubleshooting test? Disconnected via unplugging the multi-pin electrical connnector, I presume?

Yak
'83 300CD

I've never gotten my problem fixed correctly as I'm not much of an electrician. If you want to narrow down the search for the problem you remove one fuse at a time (as someone already suggested) and with one fuse out you take the negative battery cable and touch it to the negative battery terminal. If it sparks that means that something on that fuse is drawing power. You can either do more searching off that fuse or just take it out.

I had this problem with my number 2 fuse and had the fuse out for awhile. However, the number 2 fuse controls hazards and interior lights so it wasn't really an ideal solution.

I recently learned of Battery Brains. I had never seen these products before but it was on a pretty good sale at a place I was already ordering other things from. It allows you to use a remote when you turn off your car you can disconnect the battery without having to open the hood. If you don't turn it off it will turn your battery off itself when it gets down to a certain level and then you just have to open the hood and press the yellow button and start your car. It works great so far.

I should mention I also bought an optional accessory that made installation easier. It is a sensor that is used to sense whether the engine is on or not. Otherwise you have to splice a sensor into a line.

Thank you very much for the replies.

79Mercy
Q: "What kind of radio does your car have?"
A: The original Becker Europa radio is installed in the vehicle (what a relic too!)

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kmaysob
Q: "when you connect the battery does it arc?"
A: I do not *believe* that it arcs (I'm working from memory). There *might* be a slight pop, however.
After I jump started the vehicle yesterday, I drove it around a ways to re-charge the battery. It turns out, however, that I probably under-charged it just a bit because it wasn't quite up to starting this morning. After work today, I'll jump start it, drive on the freeway to get the battery sufficiently charged, and then I'll disconnect and re-connect and post here whether or not I get an arc when I connect the battery.

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::matthew
Q: "when you do drive it, are they short little trips or longer trips including highway time?"
A: No highway time. Typically my Mon-Fri. work driving is about 26 mi. roundtrip where I drive an average of about 40 mph. About 30 mins. of driving total each way. We also have a 1985 300CD-T (Calif.) and when I'm not driving the '83, I'm driving the '85 the very same route/routine and (thankfully!) it does not have this electrical problem.

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Oracle12345 (try to fix it right) - I couldn't agree with you more!!!
"Pull the fuses 1 x1 until the drain goes away

Do an amp draw test then report back.

X2 on aftermarket radio "
Q: Do you mean to pull a fuse, wait a few months, see what happens and repeat?
Q: Could you explain an amp draw test to me?
No aftermarket radio as mentioned above.

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Yak
I replaced the original starter (with a rebuilt Bosch) in Feb. of 2007 when I replaced the cylinder head and head gasket on the vehicle (fun job! - never done one before! - successful - whew!). This electrical problem has existed before and after the starter replacement.

Q: "...when you say "pre-glow" position with no lights, are you referring to position I?"
A: No. I am referring to (don't have the manual in front of me)... is it position II (I think so)? It is the position where many of the instrument cluster lamps (including the glow coil symbol) illuminate.

As for batteries, I have the correctly sized Interstate in the vehicle presently [(have the very same battery in out '85 300CD-T (Calif.)]. I am not with the car at the moment so cannot tell you the exact battery. Prior to that, it was a Batteries Plus battery. Prior to that, it was M-B batteries (multiple) from M-B dealers over the years.

I have a Fluke digital multi-meter.
Q: If I remove a given fuse, how do I measure a current draw between the two contact points for that fuse? Am I simply measuring volts DC and comparing that to the volts DC I can measure between the battery terminals?

Q: "Does background # 3 - the battery light - ALWAYS behave this way, with every start showing an insufficient charge?
A: Yes, ALWAYS.

Q: "Does background # 5, the antenna refer to the original factory antenna or an aftermarket? Is it still disconnected, or was that a temporary troubleshooting test? Disconnected via unplugging the multi-pin electrical connnector, I presume?
A: The original Hirschmann was destroyed by someone before I acquired the car (many, many years ago). I acquired and installed a replacement Hirschmann.
It is currently connected. To troubleshoot about 18 months ago, I disconnected it at the plug where it connects to the wiring harness in the trunk (left wheel well) and left it disconnected. Several months later, the battery went dead.

Thanks for the ideas and information. Please keep it coming!!!

I must have been more tired than I thought when I wrote this post. What the hell?

What I should have said in regards to testing is this:
With you car off. Touch the negative cable to the negative post. If it sparks something is drawing power.
Next step. Pull the number 1 fuse. Touch the negative cable to the negative post. If it sparks you have not found your fuse that is drawing power. Put it back in.
Pull the number 2 fuse. Touch the negative cable to the negative post. If it sparks you have not found your fuse that is drawing power. Put it back in.
Continue down the fuse line until you take a fuse out and touch the negative cable to the negative post and it does not spark. That fuse is the one drawing power. Look at your fuse diagram and see what things are off that fuse. Those are all the likely culprits. To do the job right you then have to test each of those things with you multimeter and figure out what individual item is drawing power and fix it.

You really need to get a multimeter. There might not be any draw on the battery at all, it could just be that your alternator is barely charging the battery. Get a multimeter and read the battery voltage:

1) With the car switched off
2) with the car started, and the alternatror light on at first idle
3) With the car started, just after you rev it so that the light goes out
3) With the car started, at 2500RPM in neutral

Then, with the car switched out and ignition key out, disconnect the negative battery terminal and measure the current draw (amps) between the negative terminal on the battery and the negative cable (or any exposed metal in the engine bay) on the car.

If you can answer all of these questions your problem will be very easy to diagnose!

__________________
1991 W124 250D - 130k Miles

Helpful info. - thank you!

bio_benz
The process you described makes sense to me. I'm at work now, however, tonight I'll follow the steps you described and post results.

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tombance
I have a Fluke digital multi-meter.
I understand the process and steps you described. I'll do them tonight and post results.

Thanks all and keep the helpful ideas coming!!

Be careful using a multi-meter if you're not familiar with circuit theory and how it's measuring what. The recommendations have been to measure both voltage and current. Based on the questions about measuring current draw, I'll assume you're not too familiar. Apologies in advance if that's a bad assumption but I'd rather not have you short out your battery and zap yourself.

Trying not to geek out too much: in a voltmeter mode, it'll operate as an open circuit and measure the electrical potential across two points; in an ammeter mode (for current or amps) it operates as a short circuit and measures how much current flows through the meter.

For example, if you were in a voltmeter mode and connected the probes to the positive and negative terminals of your battery, you'd safely measure about 12 V; but if you're in an ammeter mode doing the same thing it will operate as a short circuit, and probably spark and weld your terminals together.

Your meter will have a max fused capacity for measuring current, probably labelled on the front of the meter. Unless it's a super heavy duty meter, it won't have the capacity to measure your total current draw unless everything is shut off. That's one reason tombance says to measure current from the battery with the car off, but recommends voltage with the car on. You will have some minor current draw when the car is off, since your clocks keep time (radio and dash, I presume).

Answering the specific question about current draw on a specific circuit in the fuse box: In ammeter mode, the meter basically will take the place of the fuse. You set the meter correctly for measuring amps, move the leads to the correct plug-ins on the meter (if required), remove the fuse and connect the red probe to one end of the fuse connection and the black probe to the other end. The ammeter makes the connection and permits electricity to flow. No amps on that fuse means that circuit is not currently drawing electricity. But...since your problem seems either very drawn out, or perhaps intermittent, you may not show a problem and have a bunch of zeroes or a few milliamps.

I'd lean towards a bad/weak charging system, perhaps combined with something else.

One more operator error question: when you turn your headlights off, are you SURE you don't go one detent past off (straight up vertical) and into the "parking by the side of the road at night" mode? One detent past would turn on your right side blinkers into a steady mode and leave them on. It'd be easy to overlook getting out on the driver's side since they're dim lights. They work independently of the ignition - basically wired straight from the battery to the light switch.

One more equipment question: stock headlights & taillights, or euro's or other fog light mods?

Again - apologies for the ammeter lesson, but asking someone to poke metal probes onto a battery can be a risky proposition.

One more question: does your car have the "external A/C fuse" mod, or is it still drawing power through fuse 8?

I can't think of any real reason why this, by itself, would draw your battery down on a periodic basis but it may be a combination of things. If you have the external fuse (a small box on the RF wheel well) you should be able to safely remove and leave out fuse 8.

Thanks for the electrical instructions. I'm not completely uninformed about electrical, however, I certainly appreciate getting the clarification. This was useful. I'll be getting into this tonight and will post results.

Q: "...are you SURE you don't go one detent past off (straight up vertical) and into the "parking by the side of the road at night" mode?"
A: I am absolutely sure that this is not the case. I'm definitely familiar with this feature of the car and in our dark garage, I'd notice it in an instant.

Q: "...stock headlights & taillights, or euro's or other fog light mods?"
A: Stock. Stock everything except the four rims are chrome (versus the stock flat gray)

As for the "external A/C fuse" mod", I don't believe that this has been done on the vehicle. I will confirm when I get home shortly by looking for a small box on the RF wheel well. Some of the ignition wiring is in this area, of course, but I don't recall some kind of non-stock addition there. We (the wife and me) have owned this car since about 1986 and haven't added any such thing.

Thanks once again!