E300/W210: Battery drain - help! - PeachParts Mercedes-Benz Forum

scott19_68 · #1 02-23-2008, 08:53 PM

Driving home last week and all of a sudden a 'brake pad wear' warning was displayed on the console-thing - I knew my brakes were in need of a service so I thought that it was not unexpected. What I was not expecting was the slew of BAS/ASR warnings displayed about 5 minutes later. I was only a few miles from home at this point - turning up the street my radio turned off and I was stuck in 3rd gear until I pulled into my garage.

The next morning I tried to start it up but the battery did not have enough juice to turn over the engine - I figured that would explain the weird electrical issues the night before. Since my battery is less than a two years old, I thought this issue was just a bad alternator - but after a installing a rebuilt one there has been no change. The battery voltage while the engine is idling is about 10.5 volts which is obviously not correct.

After reading as many old posts as I could find related to my issues, I have performed the following with no luck:

- Installed rebuilt alternator (as mentioned above)
- Cleaned battery terminals & chassis grounding point
- Disassembled and cleaned power distribution connector (X12/3)
- Disassembled and cleaned grounding poiints in engine compartment

Any help is greatly appreciated!

Brian Carlton · #2 02-23-2008, 09:04 PM

What's the battery voltage with the engine running at 1500 rpm with the headlights on and the blower running at max?

raMBow · #3 02-23-2008, 09:07 PM

I have had no issues like these. Sometimes weird electrical issues are attributed to the K40 relay. However, your symptoms do not sound like ones I recall with that issue, but you may wish to look that up and see if anything sounds familiar.

So that is a random guess on my behalf, sorry.

raMBow · #4 02-23-2008, 09:17 PM

check out this thread... mentions low batter symptoms and K40.

'96 E300 W210 low battery symptoms

E300 (diesel)1996 cuts out at idle and while crusing.

main one on K40

K40 Relay

Looks worth checking this out.

RAYMOND485 · #5 02-23-2008, 09:49 PM

1984 300d Turbo 146k
Replace Your Battery And Alternator Needs To Be 13.2-14.2 Volts
Autozone $90.00 Plus Core $12.00 Do A Search Battery Drain

nhdoc · #6 02-23-2008, 10:03 PM

Yeah, just because the battery is only 2 years old doesn't mean it is good. One bad cell in 6 can cause low voltage. Have the battery tested, most auto parts stores will test it for free. That will at least either confirm or eliminate this as being responsible.

scott19_68 · #7 02-24-2008, 09:57 AM

Thanks for the advice - here's a small update:

- Detached battery terminals and put on a trickle charger all night - this morning, charger was showing about 1-2A @ 13.8V.
- Pulled K40 and checked connectors and PCB - found an odd 'solder bridge' made up of what appeared to be tiny metal flakes (see attached). Cleaned up PCB on K40 and reinstalled.
- Put multi-meter in amps mode and put in series from positive terminal to car positive terminal - was showing about 0.75A. Connected battery to car terminals and checked battery voltage - now showing about 13.4V.
- Car started right up and seems to run great. CCU in diagnostic mode on sensor #24 showed 11.0 - turned on headlights and showed 10.8 - set blower to max and showed 10.7 - increasing engine RPMs did not make reported voltage fluctuate - turned both off and went back to 11.0 - battery voltage checked with multi-meter was 11.5V while idling (I assume the multi-meter is more accurate than diagnostic reported by CCU)
- Turned off ignition and checked battery voltage - showed 12.6V

Not sure what might be happening but I'm going to pickup a new battery later today.

pimpernell · #8 02-24-2008, 11:45 AM

I would be especially concerned about that solder bridge, which could be causing a short. As for your voltage readings they are very much on the low side. I have a Scanguage attached to my vehicle, and when first started, with the lights on, rear defroster, and front defroster activated, and the afterglow process engaged, my voltage measures 11.8 at idle. With the afterglow process completed, my voltage jumps to 13.2 at idle, and 13.5-13.7 at about 40 mph. Good luck with your problem.

TMAllison · #9 02-24-2008, 12:04 PM

I've got an old known good K40 relay. I'll check the bottom of it and see what that area looks like.

There are two alts that were used. Up until prod date 11/97 they were 90A, thereafter 115A. Did you get the correct model?

Did you repalce the regulator too?

The BAS/ASR lights sounds like batt voltage. ECU loses communication and reports system warning on dash.

TMAllison · #10 02-24-2008, 03:03 PM

Those two points are not connected to each other on the back of my relay.

Didnt want to pry it apart to see if they connect on the inside of the PCB. Too many pins to try to get back together.

scott19_68 · #11 02-24-2008, 03:44 PM

I did not measure any continuity across the solder bridge but there was some resistance - fairly large (k-Ohms) if I recall. Bridge was easily wiped away with a cloth. I purchased the newer 115A alternator as that is what was original - the regulator is internal to the alternator, correct? I'll have the old one tested just to be sure. Thanks for checking your K40 Terry.

Update: Bought new 'group 49' battery at Sam's - same results (idling voltage remains at ~11V even after 2-3 minutes) - revving the engine does not change reading. Belt is not squealing - I assume it is not slipping since tensioning system spring is not broken. I wondered if the glow plug relay could be 'fused' but not reporting the error code - removed relay and checked for continuity between +12V input pin and all 6 outputs (there was none). I did notice about 9k resistance between ground and each of the 6 outputs - does that sound OK/correct?

From inside the car you would not know the charging voltage is really low - starts right up and there is no indicator light or warning message...

Parrot of Doom · #12 02-24-2008, 04:00 PM

Looks more like arcing to me, the bridge being composed of the tinned copper PCB.

If its been modified by someone, they're an idiot. If you wanted to hardwire something like that then you'd just use wire.

pimpernell · #13 02-24-2008, 04:09 PM

Quote:

Originally Posted by scott19_68

I did not measure any continuity across the solder bridge but there was some resistance - fairly large (k-Ohms) if I recall. Bridge was easily wiped away with a cloth. I purchased the newer 115A alternator as that is what was original - the regulator is internal to the alternator, correct? I'll have the old one tested just to be sure. Thanks for checking your K40 Terry.

Update: Bought new 'group 49' battery at Sam's - same results (idling voltage remains at ~11V even after 2-3 minutes) - revving the engine does not change reading. Belt is not squealing - I assume it is not slipping since tensioning system spring is not broken. I wondered if the glow plug relay could be 'fused' but not reporting the error code - removed relay and checked for continuity between +12V input pin and all 6 outputs (there was none). I did notice about 9k resistance between ground and each of the 6 outputs - does that sound OK/correct?

From inside the car you would not know the charging voltage is really low - starts right up and there is no indicator light or warning message...

I would still be very leery of that relay....below is some more info regarding this issue. Even though you have wiped away the "bridge", the component on the other side of the board could be fried, and not functioning as designed.....just my thoughts...

Electric Breakdown
There are four possible failure mechanisms related to the
initiation of an electrical arc across or through dielectric
material: dust-buildup, air breakdown, surface flashover, and
dielectric failure. The path of arc formation primarily
differentiates the four failure mechanisms.

Dust-buildup occurs when dust attracted by a direct current
(DC) electric field spans adjacent conductors. The absorption
of moisture by the dust over time can result in current leakage
and eventually produce a short circuit.

TMAllison · #14 02-24-2008, 05:08 PM

Unless you swapped in your old reg the new alt must come with it atached.

http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=25L0RF04Y2B310OCNL&year=1998&make=MB&model=E-300DT-001&category=F&part=Voltage+Regulator

scott19_68 · #15 02-24-2008, 06:50 PM

Another update: Cleaned the contacts/terminals on the alternator and coolant circulation pump - disconnected condenser fan (does not work anyway) just in case it is drawing too much current - still only 11V while idling

I think I'll be ordering a new K40 just in case - and to have one as a backup in case it is OK. I am still perplexed by that 'bridge' that was present before I cleaned it away - there was no evidence of any other bridge anywhere else on the board or even any contaminants. Could that be the remains of an undersized wire from a modification by the PO?

Just in case there are any K40 experts out there I've attached a picture of the connections so check if anything is odd or out of place. Notice the spliced wires on the left side of the attached photo - not sure how those got there...