LOW COOLANT lamp on permenently. - PeachParts Mercedes-Benz Forum

dkveuro · #1 01-19-2004, 03:34 AM

Hallo everyone....I have posted this to iATN tonight but thought there might be some info available from here too....well, I can only hope !
Driving Miss Daisy this ain't.... Crazy more like !

POST AS FOLLOWS about a 1998 S320W straight 6 twin cam sedan.. VIN # WDBGA32G6VA334301. Build date : 7/97

CLOSED W/SUMMARY

Well, hallo everyone ! It is 00:23 on Monday morning. Just
finished all I could do on this MBZ........You wanna know
what happened ? Okay, get a cup of coffee and a comfortable
chair and 15 minutes spare time, this is gonna be a l-o-n-g
one. You ready? Right, MBZ of OKC eventually sent me two
looms as per last problem with mirror wires shorting. These
turned out to be incorrect looms,called back and eventually
drove to Mercedes of OKC and dropped off looms hoping to
see about correct looms. Seems parts man knew I was coming
and I was told he's off for the day ! So, next day I call
and he says he's going to have to look up what was
available to fix this loom deal. A few days later he called
and said he has gotten information that says that only cure
is to install complete mirror assemblies. Okay, so how much
are they ? $616.00 each ! Pretending not to be suprised, I
ordered the drivers door mirror only, 'cose I'd run out of
money buyin' loads of parts for all these other MB's
sittin' in my shop.A week later it arrives, because, as we
all know, the reason there are holidays is so parts guys
and UPS can screw you around with delivery delays.....Nuff
said ! Anyways, this parcel arrived with a COD balance to
pay against the credit on the looms. Okay, part
#210-810-21-16 LT MIRROR. is checked for busted up whilst
in UPS custody....all okay. Now this afternoon at 14.00 hrs
I gave in to the need to see if I could install mirror
without recourse to dynamite. Here's the skinny for those
of you contemplating replacing a door mirror on a 140 with
power folding mirrors, (I guess the power fold back is good
for another 12 mph on the autobahn, heck, who the blazes is
gonna be concerned about looking in the mirrors to see
who's behind you at 145 mph anyway ? ) Anyway, I digress,
with the mirror folded half way back, close the door and
grab the mirror body and pull it forward and out to expose
the clockwork. Don't worry about the creaking and snapping
noises...If you look all the way in from the mirror side at
the joint, you will see a spring steel wire running top to
bottom held in the center by a tiny finger. With a probe,
spring this wire out from it's position behind the finger,
this allows the two ears at top and bottom to disengage the
mirror body and you can slide the plastic body off the
motorized mirror assembly. Next, you will see three
phillip's head screws holding the assembly to the
door.Remove these and swing mirror away from body with the
rubber gasket, then you'll see the two loom connectors to
the mirror, these pull apart without needing to release any
clips or hooks, and, as they say in most of those dumb
books, 'reassembly is reverse of disassembly.' My problem
was that I had to fix the loom shorting in the right door
mirror too, so I pulled the body off the assembly and cut
the wires to the mirror swivel head, leaving the folding
feature wiring in place so no short would happen, but now
there is no mirror adjustment on that side, only fold. It's
a wide angle mirror so position is not too critical....So,
didn't need two hulking great looms, only mirror head. Job
done, just need owner to authorize right mirror relacement
at another $616.00 plus. So button up the new 'WASHER'
sensor and put all the engine covers back in. Guess wot ?
New 'COOLANT' sensor too. The flaming 'LOW COOLANT' lamp is
still ON !!!! Okay, installed extra ground wire after
cleaning up the two inner fender stud grounds, but lamp
still on...I guess some black electrical tape will have to
do over the warning lamp, I see no reason apart from the
rat may have got into wire loom I can't see or acsess in
the engine bay, although I spent a lot of time looking. Any
more ideas folks ? Everything back in I had removed to get
at a rat's nest under the A/C intake plenum.....Stinky job,
used a painters face mask doing that job as don't need to
contract Bubonic Plague ! Washed it down with diluted
hydrogen peroxide. Next put the Snap-On scanner in to check
all's well. Two codes come up, Missfire #4 cylinder.!!!!!
WHAT ? Ran engine up and sure enough, miss, engine rough.
Took intake off and removed plug cover....DUH, water had
run into cover valley and trickled down into #4 plug
resess. Dry everything out and clear codes...run to warm
and recheck, missfire comes back ! Out comes stetherscope
and I listen to injectors. # 4 not clicking. I know that
the ECU will shut off an injector if missfire values get
above a set value. So, remove coil for #4 and checked for
spark, big fat spark and no fall out. Wiped with dilectric
grease and refitted to engine. Cleared missfire codes and
ran to warm again.....Oh yes, by this time it's 21:30 hrs !
Engine ran smooth. Tried to kill injectors with Snap-On
scanner in 'actuations' feature, but system would not allow
it. Tried 'OFF' '' and 'HELP' menue but still would not
kill selected injectors. On this cartridge there is no
'TROUBLESHOOTER' menu, wanna tell us why, Snap-On.

So, all codes cleared and closed up for test drive. Washed
up and headed out for the WAFFEL HOUSE. About 5 miles into
trip with 'cruise' set at 65mph the ASR lamp comes on,
cycled key off/on quickly and lamp stayed out for rest of
trip of 12 miles plus trip home of 16 miles...Strange !
Also noted the brake pedal is dropping some at stops. Back
at the shop I bleed all wheels, no air, no change, still a
lot of pedal drop at stops. ABS functions okay and stopping
the car is fine but needs a little more travel than I would
like to see. Mmmmmmmmm ? So the upshot of all this is, why
is my LOW COOLANT lamp still on ?.......Hey, you fallen
asleep out there ?.....BTW, code clearing will not always
work if you don't take the key out for a few seconds before
restart or retest, so if any of you are still with me after
all this I'd appreciate any tips you might have. Failing
that, it's a day's subscription to www.Mercedes on line web
site. Being as this is my last post for this HELP mail, you
can email me at dkveuro@juno.com if you have info' or
wiring schematics. For those of you who sent emails about
the COOLANT lamp, thank you for taking the time and trouble
to reply. They where all gratefully recieved. Thanx once
again.......Regards everyone, dk.

END OF iATN POST.

To continue.........

Hope I didn't offend anyone doing this.....need help bad on this.
Becoming the car from hell. BTW, would front to rear worn tyres cause this system to flash the ASR ? All tyres are same size though. Just that back tyres need replacing.
Thank you....dk

stevebfl · #2 01-19-2004, 08:28 AM

I'm thinking that car still uses the series circuit between the coolant and windshield washer fluid sensors. For some reason the IC (instrument cluster) figures out the wrong one.

Try disconnecting the washer reservoir sensor and see what happens. (I don't know what should happen so goog luck)

dkveuro · #3 01-19-2004, 12:38 PM

Steve, disconnecting either coolant or washer sensors has no effect on the warning lamp. It remains on.
Both sensors are new from MB . The voltage on the Brown/Blue wire is 8.46 vdc and 0.085 vdc on the Brown wire and 0.0056 ohms on the Brown wire to ground, measured at the plug connectors or at a peiced point down stream.
I think the 'black electrical tape' idea is workable !!
dk

dkveuro · #4 01-19-2004, 04:46 PM

I told customer about problem and he now tells me the heater manifold block against the fire wall broke and engine overheated. This is when the Low Coolant lamp came on. Been on ever since then he says. Any possible connection with another sensor ?
Wish I had schematics for this....dontcha just love it when they feed you a little bit of history at a time !!!!? Grrrrrrrr.
dk

Gilly · #5 01-19-2004, 04:58 PM

That sensor won't go in upside-down, will it?
Steve, I think the set-up you're talking about that links the 2 sensors together originated with the SLK 170 chassis, I don't think the 140 works that way, individual circuits.

Gilly

mbdoc · #6 01-19-2004, 05:26 PM

The W/washer level sensor is in series with the coolant level sensor on most 1997 (1996 on the W210)& later cars. The cluster MUST see some(but not full) return voltage OR the coolant light will stay ON!
The coolant sensor is a ON/OFF circuit & the w/washer sensor is a variable resistor.

stevebfl · #7 01-19-2004, 05:28 PM

Some reason I read E320. Ooops

myarmar · #8 01-19-2004, 07:24 PM

I have schematic for 140 as of 97.
S41 ECL switch has 170 Ohm resistor inside. S42 Windshield Washer switch has 110 Ohm resistor. The switches are in series and normaly open. So in normal condition IC would see 110+170=280Ohm.
If one of the switches gets closed resistor in this switch would be shorted out, and IC would see either 110 or 170 Ohm.
Reg. Mike

dkveuro · #9 01-19-2004, 07:38 PM

Okay guys...I've been known to get a chassis type wrong before, so let's clear up the cars id.

1998 S320W straight 6, twin cam, automatic, sedan..

VIN # WDBGA32G6VA334301..... Build date : 7/97

I hope I didn't throw a curve ball in there saying anything about a 140 .... Steve, you and me have gotta pay more attention old son !
I'm going to introduce a little more voltage into the circuit with a variable resistor pot and let you all know what happens..
Thank you for the latest info' people.
dk.

dkveuro · #10 01-19-2004, 07:52 PM

Did I say 'Pay attention !' Well I thought I'd double check the VIN and Build Date....Guess what? Build Date should read 07/96...
NOT, 97

.Crap, this is wot comes of working untill 3am on Monday morning.....SORRY folks.
Okay, I'm going to do that test voltage now....see you later...dk.

Gilly · #11 01-19-2004, 08:18 PM

IF you really can't find a problem with the sensor chain, there is one other thing I've seen. I wouldn't have thought it would pertain to this chassis, but then again I didn't think a 140 ever used the sensor chain logic either.
I did see a 202 chassis that we absolutely couldn't figure out why the low coolant lamp kept coming on. Turns out there is some sort of relationship between either the cluster and the engine control module or the cluster and the ACC which will throw on the low coolant lamp in the event of an aux fan failure. Any chance the aux fans are inop on this thing?

Gilly

dkveuro · #12 01-19-2004, 08:42 PM

Mmmmmmmm. That's interesting. The a/c was on last nite in the shop while I was hooked up with the scanner, I never heard the fans kick in , and that was for over 45 minutes too. They get sucked into rotation at high engine speeds but never seem to run up. I think I'll check that right now....BTW, what commands FANS ?
Pressure/heat sensors in a/c lines? My scanner does not feature fans, on/off.
dk

Gilly · #13 01-19-2004, 09:25 PM

On that model, there should be a fan control module I believe, could be wrong on that. The fans are triggered by pretty much what you are used to:
AC pressure and/or engine temps.
Use your scanner to go into ACC to see if you can run a aux fan activation routine, that's where you get to it in the MB scanners.

Gilly

dkveuro · #14 01-19-2004, 09:27 PM

Update...Car in shop.
A/C on. Set to 'LO' both sides.
Drivers side auxillary fan runs but passenger side does not.
A/C off.
Run temperature up to 205f. (Raytek, pointed at underside of thermostat housing.) with #2 fuse for FAN pulled. Intall fuse and drivers side fan runs but not passenger side fan.
All fuses eyeballed and ohms tested good.
'Low Coolant' lamp still lit.
Only one aux' fan running.

Gilly · #15 01-19-2004, 09:43 PM

Unknown if a bad fan itself would cause the light to come on or not, or even if this problem I remember with the 202 would apply to this beast. I would rather think that an actual control problem, like a bad fan control module, would cause the light, but who knows? Maybe too little current draw from the fans would also cause it? Sadly I can't remember what the neccesary repair was on that 202 car, just that a aux fan problem = a low coolant light, some sorta MB "fuzzy logic". At any rate I would think with the big 12 holer you'd definitely be better off advising the customer to replace one of the aux fans rather than worry about the outside mirror. I mean, assuming they can actually USE that mirror to a good effect.

Gilly