Ground in non fused circuit?
 

I have ground that does not go away when the fuses are removed one at a time.

1995 S350 W140

I put a verified charged to 100% brand new battery in the car last night. This morning it was down to 60%.

I recharged the battery and:

I connected the positive terminal of the recharged to 100% brand new battery to the cars positive cable like normal.

I connected my multimeter in series between the negative cable on the car and the negative terminal on the battery.

With the multimeter set to DC Amps it is reading 4.4 amps.

Then I went through the front and back fuse boxes and pulled each fuse one at a time, replacing the fuses after verifying that the current did not change.

Is there a non-fused load in here that may be the problem?

What do I check next?

Should I pull all of the fuses? (Could there be multiple grounds? Shouldn't I have seen at least a partial change in current while checking each fuse one at a time if there are multiple gounds?)

Help!

-Jim

The regulator or the diode bridge in the alternator could be going out and causing the drain, if nothing else is.

I wouldn't think that your current draw would be stable if you had it spread around multiple circuits, and having them all fail at once is not too likely.

If you have a Schucks, O'reilly's or the like that can do the free alternator tests, I'd consider pulling it and having it tested.


I'm not too familiar with that particular model, so I can't say just what else might be unfused, or not fused in the main fuse box.

Thanks, that gives me something to search on here on the forum.

I'll read up before I pull the alternator. It has a serpintine belt. My mechanic was not a happy camper when he put the new one on after replacing my air conditioning compressor.

-Jim

Rogue AMP Draw
 

EDIT: Allen beat me to it.

(NOW, you know who can answer this question...[+ it ain't me.] )
(just have to wait until gsxr or one of the professional wrench turners see it.)

I hate to complicate your diagnostic endeavors...BUT,the MAIN ground for the
whole electric system is that wire from the Battery Negative Pole to the Body.
(so [putting your DMM in series at that point] in effect you are measuring the AMP draw from the negative side of the consumer through the body < ground wire < consumer<positive wire<Battery[Positive].)
I'll bet if you put the DMM in series in between the Battery Positive pole and
the positive clamp you'll still get the 4.4 AMPS Draw.

That's a big draw...I'd be suspicious of the rectifier bridge/diodes in the Alternator(It has been known that when one goes bad it suctions off the Electrons.) Yes,the test would be put the DMM in series between the positive lead from the Alternator (Big Wire)and the distribution block on the passenger wheel house.[KO,EO of course][Key Off,Engine Off]

The alternator is at the bottom of the engine bay, of course.

I am away from home right now in a campground. I have the car's jack (yuck!) and jack stands, but no safe place to jack the front end up.

Where does the positive lead from the alternator go to? Is it the second wire that attaches to the positive clamp on the battery?

I followed the smaller wire that comes off of the positive terminal. I goes to a terminal block about 1 foot from the positive terminal. From there it branches over to the fuse box in the trunk and forward (to the main fuse box?).

Strangely, with the ground wire connected to the battery and the multimeter in series from the positive terminal on the battery to the wire that goes to the rear fuse box I get 7 amps!

-Jim

Found a related thread:

http://www.peachparts.com/shopforum/showthread.php?t=179478&highlight=w140+alternator

-Jim

Found a possibly related thread.

http://www.peachparts.com/shopforum/showthread.php?t=34658&highlight=w140+battery+drain

They are having trouble with the trunk closing mechanism and the battery draining.

I have noticed that I have to firmly shut the trunk and hold it shut to get it to stay shut. I'll follow their ideas and see if it is the current drain.

-Jim

Trunk
 

is Staying On...bet that's one of them.
Weird that you are showing two different amp Draw rates?
Unless you've actually got two (2) separate Amp draws.
1.Trunk
AND
2.Alternator rectifier/diode bridge.

See if these help any:

#2
 

#2

Thanks! That helps me understand what is going on a little better. It also makes me wonder why they set it up like they did. Seems like they could have eliminated a connector and run the rear fuse box right off of the battery. It is what it is.

Now to find the front junction (#29 Cable Connector) and lift the wire going to the starter & alternator to check the current from there to ground. #62 is the main cable. At the end of it is #77 to the alternator and #80 to the starter. Lifting #62 at the #29 Cable Connector will let me check out the alternator without having to jack the car up...hopefully.

It will have to wait for Saturday. I will drive the car home tonight and check it at home. Right now I have the lead lifted on the battery to keep it from draining.

-Jim

I took this photo of #53 Cable Connector in the trunk last night. Passenger side on the wheel well.

-Jim

I lifted both leads off of the back of the alternator and still have the ground. It is up to 5+ amps, but that is probably because of the freshly charged battery. (Higher voltage -> higher current).

I lifted the oil level sensor supply line. No change.

Still need to find & check the oil pressure sensor, starter, and a condensor (capacitor).

Any ideas where they are or any other thing to check?

-Jim

Other?
 

The Starter's in the second Cyrillic Pictogram in reply#8 (Just behind the Alternator...or so it appears?)

( Everything Else will be here: http://www.detali.ru/cat/oem_mb1.asp?TP=1&F=140134&M=603.971&GA=722.367&CT=F&Cat=19B&SID=82 AND HERE http://www.detali.ru/cat/oem_mb1.asp?TP=1&F=140134&VIN= )

AND here's your OP sender (It's #293):

Same problem with mine as with every early to mid 90's MB...

I'm resheathing my sensor lines with heat shrink. They are in the hottest area of the engine compartment and are showing the signs first.

-Jim

I've heat shrinked all of the sensor lines, lines to the starter, and lines to the alternator. The ground is still there.

A friend of mine pointed out that diesel conducts electricty and that he has seen soaked wires and connectors cause grounds.

I had a split injector return line just before the ground appeared. It soaked the entire driver's side of the engine bay...:mad:

I guess I will concentrate there next...

-Jim

4 amps sounds like a lot of current to flow through a diesel-soaked wire laying against something grounded. Based upon your prior investigations with pulling all the fuses, it would have to be in an unprotected circuit as well.

Do you have any aftermarket electronics that may have been installed with a direct connection to the positive battery terminal?

Do you have the wiring diagrams for this car? Are there circuits that have fuses or breakers that you haven't yet eliminated?

Just looked at those pictures in an earlier post... I'd suspect the condensor (no. 38), or the starter. Have you disconnected the starter motor?

I have disconnected the starter.

No aftermarket electronics.

I have not found that stinking condensor or connector #29.

It is up to 5.5 amps now.

Battery is unhooked and I am driving a back up car (99 Maxima).

-Jim

Man, what a frustrating problem...
Keep trying, it'll be that much more gratifying when you get it licked.

Four or five amps at 12 volts is 50+ watts. That will cause some heat. Do you know anyone with a thermography scope? You can rent those in some cities.

Hmmm.... Glow plug controller? It's not fused at the fuse box....

I have not tried that yet. It would have to be on the wire leading up to the controller and/or the hot side of the controller itself. That could be a winner. Even with the battery fully charged and the charge booster attached to the battery it is hard to start when the engine is cold.

Almost like the glow plugs are not working.....;)

Starts great once the engine is warm.

-Jim

Found it! Aux Fan Relay!!!

Back on December 19th I came out of the hotel to go take a test and found the battery dead on the car. When I jumped it off to get it started the aux fan started running as soon as the cables were hooked on. By the time I got home that night the fan was not doing that any more.

This spring the ground came in, or at least I noticed it finally.

Once the weather warmed up I noticed that I was having temperature problems.

In April I bought a truck and started driving it every day. I forgot about the car for a while.

Yesterday I was filling out some paperwork and had to look up the day that I took a test, the day the fan ran all night and killed the battery. It all came rushing back...fan running on its own...fan fixes itself...temperature problems...ground... A coil on the Aux Fan Relay shorted itself to ground!!!

.01 amp draw with the engine off and the Aux Fan Relay removed! Life is good!!!

-Jim

Yeah!
 

'Nice save!


EDIT:
I've gone Off the Planet again /somehow converting your W140 s350 chassis to
a 1987 300D W124.

Corrections to make below also!

I'm not sure which one it is. It is the one pictured when you look up the Aux Fan Relay at Fastlane. MB part number 001 542 82 19.

12Vdc 40 Amps. Decent sized sucker. Circled in Red in the photo.

-Jim

Yes,it's a "Big Ole Honker"
 

You'll notice it has 8 Poles
(Quantum leap here...That is your Single Auxiliary Fan Relay...it does both Low
and High Speed relay duties.)

'90-91 OM 602
 

Gets two Auxiliary Fan Relays:

(on the '90-91 [OM602?] K9 [the High Speed Fan Relay]"Load" side is "Straight" wired to X4/10 with No Fuse In Line.)

The original Relays were not fused,
and at some point the part number superseded to the current Relays both of
which are fused.

1.001 542 96 19 (K9 High Speed Auxiliary Fan Relay) [With 30 Amp Fuse]
[This fuse is the "Load" side of the K9 which is wired directly to X4/10
Which makes this circuit "HOT" whenever the Battery is connected]
2.002 542 01 19 (K10 Low Speed Auxiliary Fan Relay) [with 15 Amp Fuse]
[MB says you may upgrade the 15 Amp Fuse to a 25 Amp Fuse]


If you take the time to follow the developments of these relays circuitry
and fusing onward you can visualize the areas that
caused dangers with: Dead Shorts , Etc.

Wow! I never went back and updated what happened. It has been 3+ years now since I had this problem. I finally identified which relay was the right one. My foggy memory says that I had to remove the fuse tray to get to it. I bought a new one on eBay from some guy in the northeast and put it in. It has worked great with no issues. Easy fix once I figured out which one it was. The problem is that I don't know what to put in here to help the next guy out! (I've forgotten pretty much all of the details.)

Jim