Fuel gauge indication - W123 - Page 2 - PeachParts Mercedes-Benz Forum

steamboatsykes · #16 02-17-2018, 11:25 AM

Quote:

Originally Posted by funola

Here's the wiring diag you're looking for https://www.startekinfo.com/StarTek/outside/12265/disc_2/program/ETM/82_300.pdf

P 120 you can see the gauge cluster power is not fused. You can do a quick test with the key on, short pin 1 and 2 on the sender connector to pin 3 (ground). The low fuel light should illuminate and the gauge should rise. If not, short pins 1 and 2 to a chassis sheet metal ground..... if it works, the ground wire on the connector is bad. If the chassis ground does not help. Check power at pin 6 ? on C151 (circular connector) on the cluster as well as the grounds.

Thanks.

okyoureabeast · #17 02-17-2018, 11:28 AM

Three things affect the gauge cluster:

1. A bad ground
2. A bad sender
3. An electrical fault between the gauge and the sender (ie a bad wire).

I'd hazard number 3.

steamboatsykes · #18 02-17-2018, 12:38 PM

Quote:

Originally Posted by funola

Since the instrument cluster is un-fused, be careful when working on it. Make sure the key is off whenever connecting/ disconnecting the connector/ grounds etc.

I didn't know the cluster is unfused untill looking at this diagram. J

That is really surprising, perhaps they figured that the circuit board traces are the fuse.

vwnate1 · #19 02-17-2018, 09:32 PM

THANK YOU for the handy 1982 Circuit Diagrams PDF .

I'm :

A. old .

B. a (damn) Yankee born & bred, yes I lived in upstate New York in the 1960's (Rochester) .

C. a pedant (? SP ?) about terms of things due to my lifetime of Mechanicing and training .

Maybe one week before I bought my first Klima II equipped Mercedes, I passed on buying the factory Klima II shop manual......

tdoublenastywitit · #20 02-18-2018, 09:52 AM

please post the solution if you figure this out!! I have this problem on two of my w123s now and I'm willing to bet I'm not the only one

steamboatsykes · #21 02-18-2018, 01:24 PM

Quote:

Originally Posted by tdoublenastywitit

please post the solution if you figure this out!! I have this problem on two of my w123s now and I'm willing to bet I'm not the only one

Its the sending unit again. Level sense wire broken and open.

tdoublenastywitit · #22 02-18-2018, 02:58 PM

Quote:

Originally Posted by steamboatsykes

Its the sending unit again. Level sense wire broken and open.

So which color wire was broken?

Mxfrank · #23 02-18-2018, 04:29 PM

Quote:

Originally Posted by funola

Since the instrument cluster is un-fused, be careful when working on it. Make sure the key is off whenever connecting/ disconnecting the connector/ grounds etc.

I didn't know the cluster is unfused untill looking at this diagram. Jake2tech smoked the wiring on his W124 by not taking the above precautions.

I guess Mercedes designed it unfused because they feel loosing all gauges due to a bad fuse is not a good thing. I think they could have done better with a self resetting circuit breaker.

You are obsessed with this idea. Even if it was right, which it isn't, I don't see the relevance. The panel is fused, with the sole exception of the charge indicator. The only thing that would work if a fuse blows is the charge indication circuit.

steamboatsykes · #24 02-18-2018, 04:50 PM

Quote:

Originally Posted by tdoublenastywitit

So which color wire was broken?

Inside the sending unit. One of the float wires.

funola · #25 02-18-2018, 07:47 PM

Quote:

Originally Posted by Mxfrank

You are obsessed with this idea. Even if it was right, which it isn't, I don't see the relevance. The panel is fused, with the sole exception of the charge indicator. The only thing that would work if a fuse blows is the charge indication circuit.

Obsessed? I glanced at the diagram and saw only the un-fused feed and didn't see the fused feeds. That is carelessness on my part, not obsessive.

I am glad you noticed it and corrected me though.

jdere31760 · #26 12-24-2019, 10:32 PM

Quote:

Originally Posted by funola

Here's the wiring diag you're looking for https://www.startekinfo.com/StarTek/outside/12265/disc_2/program/ETM/82_300.pdf

P 120 you can see the gauge cluster power is not fused. You can do a quick test with the key on, short pin 1 and 2 on the sender connector to pin 3 (ground). The low fuel light should illuminate and the gauge should rise. If not, short pins 1 and 2 to a chassis sheet metal ground..... if it works, the ground wire on the connector is bad. If the chassis ground does not help. Check power at pin 6 ? on C151 (circular connector) on the cluster as well as the grounds.

Funola, do you have a manual showing where the ground is on for 1985 300D?
I noticed that this diagram for a 1982 300D is grounded at G103, but where would that ground location be?

funola · #27 12-25-2019, 10:01 AM

Quote:

Originally Posted by jdere31760

Funola, do you have a manual showing where the ground is on for 1985 300D?
I noticed that this diagram for a 1982 300D is grounded at G103, but where would that ground location be?

I don’t think sheet metal change from year to year on W123 series, so the chassis grounds should be the same for 85.

P139 of the Startek elec diagram shows:

G103 for 300D/ CD is in trunk, behind LH wheel well

barry12345 · #28 12-25-2019, 01:42 PM

Quote:

Originally Posted by vstech

My dad always called channel lock pliers “water pumps” I have never heard anybody else call them that...

Air Force?

New Yorker?

Baby boomer...

Just curious if you know where the term is from.

I have also heard them referred to as water pump pliers. I do not know if channel locks was just the earliest developer of that type of plier. But the brand name stuck. Perhaps along the same way vice grips has. In any event both have proven very useful over a very long period.

vwnate1 · #29 12-25-2019, 01:50 PM

"Water pump Pliers" were designed to easily and rapidly tighten the gland packing nuts on water pumps 80 + years ago .

Channel Lock made the best ones, why the name stuck because no one remembers what a gland nut is anymore .

It's the same thing with a 'Crescent Wrench' ~ this is an adjustable jaw wrench that was best made by the Crescent Tool Company....

jdere31760 · #30 02-01-2020, 02:11 PM

Quote:

Originally Posted by funola

I don’t think sheet metal change from year to year on W123 series, so the chassis grounds should be the same for 85.

P139 of the Startek elec diagram shows:

G103 for 300D/ CD is in trunk, behind LH wheel well

Thanks funola, you were right!
I found the ground and cleaned it up.
My fuel guage still reads only full, no matter how much fuel is in the tank.
I ohmed out the fuel sending unit and it works fine with the ohm readings posted online. So the saga continues.....

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