fuel gauge sender needed

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Pete49
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fuel gauge sender needed

Post by Pete49 » Thu 14 Dec, 2017 2:06 pm

Well I got the wire via amazon and like Mat said it only shows to half a tank which is OK around town as the low level light works but I will be venturing interstate next year so would like a replacement. Has any one got a fuel gauge sender for a 280TE they are willing to sell me? Preferably from an 1981 or older as apparently there are some changes made before then or so I read but now can't find the info :angry4: Rather buy form members than look overseas.
Pete
1978 W123 300D Maple Yellow
1981 W123 300TD Classic White (now sold)
1983 W123 280TE Champagne

mathuisella
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Re: fuel gauge sender needed

Post by mathuisella » Thu 14 Dec, 2017 10:02 pm

in the interum...



when the fuel tank is empty, it shows half full on the gauge
when the tank is half full, it shows 3/4 on the gauge,
when the tank is full it shoes full on the gauge.
so it is usable in that regard :)

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Christo C
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Re: fuel gauge sender needed

Post by Christo C » Fri 15 Dec, 2017 7:27 am

It depends whether you are a glass-half-full or glass-half-empty sort of guy, I suppose. :dontknow: :laughing5:
~Christo
1986 230E W124.023 M102.982 ~290,000km Thistle Green Saloon "Janis"

Pete49
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Re: fuel gauge sender needed

Post by Pete49 » Fri 15 Dec, 2017 2:29 pm

Yes I see that part is good its the empty that could cause concern :Doh: But the light lets me know if I'm down to 11 litres so as long as I'm close to a town it should be ok.......or not lol. I wonder if its to do with the resistor on the sender and if changing the value would work. Not having a spare I can't really check it but can you Math?
1978 W123 300D Maple Yellow
1981 W123 300TD Classic White (now sold)
1983 W123 280TE Champagne

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Tony From West Oz
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Re: fuel gauge sender needed

Post by Tony From West Oz » Fri 15 Dec, 2017 3:57 pm

Pets, How long has the sender been faulty?
Has the instrument cluster been changed? The reason that I ask, is that there may be a difference in the fuel gauge unit itself between sedan and wagon, due to the differences in the sender between the 2 variants. You could check by trying a sender from a sedan in place of your wagon sender.

You may still be able to calibrate the gauge to read correctly.
I have never done this on a W123, but did it on my Morris Minor when I was young.
Measure the sender resistance full and empty (remove from tank, drain and then measure with float at top and bottom of travel) Then find resistors that match the full and empty values (My guess is that full is 0 ohms).
Remove the instrument panel from the dash, but plug it in to the wiring harness.
On the back of the fuel gauge there may be 1 or 2 holes for screwdriver adjustment of the gauge. By trial and error you should be able to set the full and empty readings correctly, by swapping the resistance for full and empty.
If there are no holes in the back of the temp gauge, you may need to remove that part of the cluster from the inst. panel and check if you can see an adjustment there. Possibly there will be a lever attached to the gauge spring. This will adjust the reading of the gauge.

One of these may help you get to the bottom of the issue and hopefully fix it.
Life is a journey, with problems to solve, lessons to learn, but most of all, experiences to enjoy.

'83 W123 300D 325000km (Wife's car Josephine - sold).
'84 W123 300D replaced good OM617 912 with OM617 952 and enjoyed having good acceleration for the first time since first driving a 300D in 2002 - became engine and trans donor for 300CD Turbodiesel conversion. Now parted out.
'86 W124 300D sold (Wife's old car - sold )
'85 W123 300CD, 275 000km (Fatmobile) rebuilt turbodiesel from previous Fatmobile transplanted into 280CE (occasional tourer)
'99 W202 C250 Turbodiesel (my darling Wife's car - Sold)
'98 W202 C250 Turbodiesel (my car - Sold)
'06 Ssanyong Musso Crew Cab 2WD Ute (OM662 diesel and Auto Transmission)

tsharkey
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Re: fuel gauge sender needed

Post by tsharkey » Fri 15 Dec, 2017 10:30 pm

Tony From West Oz wrote:
Fri 15 Dec, 2017 3:57 pm
The reason that I ask, is that there may be a difference in the fuel gauge unit itself between sedan and wagon, due to the differences in the sender between the 2 variants. You could check by trying a sender from a sedan in place of your wagon sender.
Good thinking but can verify the gauges interchange happily.
W123 1981 300TD - Family Kid mover
W202 1998 C250D Factory OM605A Turbo - Partner's daily driver
W123 1982 300CD Retro fitted OM617A Turbo - Mine
W123 1984 300TD 5 Speed Manual, to teach the kids how to drive
W123 1982 300TD Factory OM617A Turbo (Hans) - Project
W123 1985 230TE - Brother's
W123 1985 300D - Sister in Law's
1962 S-Series Valiant (Tho Daimler & Chrysler divorced, still part of the extended family)

Past benzes
W114 1969 250CE - PO put in an M110 transplant and nearly sent me around the bend
W123 1981 300TD - "Matilda" - RIP hit front side & rear but left my brother + niece A-OK

Current Projects
Coupe restoration, Turbo Wagon freshen up

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Tony From West Oz
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Re: fuel gauge sender needed

Post by Tony From West Oz » Fri 15 Dec, 2017 11:15 pm

tsharkey wrote:
Fri 15 Dec, 2017 10:30 pm
Tony From West Oz wrote:
Fri 15 Dec, 2017 3:57 pm
The reason that I ask, is that there may be a difference in the fuel gauge unit itself between sedan and wagon, due to the differences in the sender between the 2 variants. You could check by trying a sender from a sedan in place of your wagon sender.
Good thinking but can verify the gauges interchange happily.
By Interchange happily, do you mean that the fault is present with both sender units? If so, the gauge itself is faulty.
If you mean that the gauges for sedan and wagon are interchangeable then we still need to check the sender unit against a known good one from either body style.
Life is a journey, with problems to solve, lessons to learn, but most of all, experiences to enjoy.

'83 W123 300D 325000km (Wife's car Josephine - sold).
'84 W123 300D replaced good OM617 912 with OM617 952 and enjoyed having good acceleration for the first time since first driving a 300D in 2002 - became engine and trans donor for 300CD Turbodiesel conversion. Now parted out.
'86 W124 300D sold (Wife's old car - sold )
'85 W123 300CD, 275 000km (Fatmobile) rebuilt turbodiesel from previous Fatmobile transplanted into 280CE (occasional tourer)
'99 W202 C250 Turbodiesel (my darling Wife's car - Sold)
'98 W202 C250 Turbodiesel (my car - Sold)
'06 Ssanyong Musso Crew Cab 2WD Ute (OM662 diesel and Auto Transmission)

mathuisella
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Re: fuel gauge sender needed

Post by mathuisella » Sat 16 Dec, 2017 3:19 am

sedan and wagon fuel senders are not interchangable

they are not physically the same, sedan is twice as long.

hence the wire length is twice the length in the sedan which makes twice the resistance value. the cluster fuel gauge is the same across all w123s ive seen, coupe, sedan and wagon, petroleum and diesel.

i remember the wagon had a 320 or 330 ohm resistor in parallel with the wire. in parallel it lowers resistance so the wagon wire is difference.


also, the reserve light will light up in your case when the tank is low and the needle reads half full. This is because the needle and light run independent of each other, only link is the fuel level float. So in the short term you are ok.

I would find out what half the cross sectional area of awg 37 would be and find nichrome 80/20 in that size. or find the resistance of the wire in there now and find other wire of equal length with twice the resistance.

Pete49
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Re: fuel gauge sender needed

Post by Pete49 » Sat 16 Dec, 2017 2:18 pm

Tony the sender was fine until a few weeks ago. The cause was the nut on the bottom of the sender unit came off and with the fuel sloshing around the tube cut the wire. As the wire was too short to fix it I had to order some from Amazon (US) and when repaired it reads wrong due to the incorrect resistance I think. As I am not in the electronics field I was hoping someone here may be able to advise me on what resistance it may need.
1978 W123 300D Maple Yellow
1981 W123 300TD Classic White (now sold)
1983 W123 280TE Champagne

mathuisella
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Re: fuel gauge sender needed

Post by mathuisella » Sun 17 Dec, 2017 12:37 am

Pete49 wrote:
Sat 16 Dec, 2017 2:18 pm
Tony the sender was fine until a few weeks ago. The cause was the nut on the bottom of the sender unit came off and with the fuel sloshing around the tube cut the wire. As the wire was too short to fix it I had to order some from Amazon (US) and when repaired it reads wrong due to the incorrect resistance I think. As I am not in the electronics field I was hoping someone here may be able to advise me on what resistance it may need.
I'm doing Electrical Engineering at uni, so this is kinda my area.

If you still got some of the wire i linked you to, the sedan wire. Measure how much resistance that gives over 1 metre.

then write that value down.

then search for wire that has 2x that resistance per metre. Example: if i remember right it should be somewhere around the 100 Ohms per metre resistance, so you would need 200 Ohm per metre wire. ( measure 10 centimetres of the original wire ( no need to cut it, just place probes 10cm apart ) it should be somewhere around the 20 Ohm value of resistance to confirm my theory. )


Just a question. do you still have the original wire ?

( i have done the below, so it is possible )

if so, have you thought about rejoining it. ? takes a bit of skill and good steady hands. get a friend with tweezers on each end to hold the two broken ends together as you put a drop of solder on it to join it.
if there's a small gap, perhaps use a tiny bit of the 37 AWG wire to act as the joining piece, sure your value will be slightly out, by about 5%-10% but you would have full spread of the working gauge of the dash.

mathuisella
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Re: fuel gauge sender needed

Post by mathuisella » Sun 17 Dec, 2017 12:48 am

trucking finally found it.

https://www.amazon.com/Kbees-250-Nichro ... e+40+gauge


this 40 AWG wire Nichel and chrome ( 80% Nickel 20% Chromium )

being half the cross sectional area ( approx 45%) of the 37 AWG sedan standard size, it should work out doubling the resistance as every other characteristic is the same
resistance is futile.JPG
Sorry it's late,

this is the formula to use if you wish to check the numbers.

this should give you a pretty accurate gauge again :)
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Pete49
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Re: fuel gauge sender needed

Post by Pete49 » Fri 22 Dec, 2017 2:20 pm

mathuisella wrote:
Sun 17 Dec, 2017 12:48 am
trucking finally found it.

https://www.amazon.com/Kbees-250-Nichro ... e+40+gauge


this 40 AWG wire Nichel and chrome ( 80% Nickel 20% Chromium )

being half the cross sectional area ( approx 45%) of the 37 AWG sedan standard size, it should work out doubling the resistance as every other characteristic is the same ohms

resistance is futile.JPG

Sorry it's late,

this is the formula to use if you wish to check the numbers.

this should give you a pretty accurate gauge again :)
Mathuisella I just checked the wire as suggested and on the 200 ohm scale it reads 10.5 ohms. That's the 37 AWG but I think it is 21 ohms as I used the wrong setting I think. I'll double check later. I can't find the original wire to check that reading. I think the shop elves used it for Xmas decorations or rewiring their house. g Will changing the resistor get me around that? Oh I'm having trouble trying the formula you showed in the post as I can't work out what the p L & A represent. Yeh I know just a dumb old kraut but I try.
Peter
1978 W123 300D Maple Yellow
1981 W123 300TD Classic White (now sold)
1983 W123 280TE Champagne

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Tony From West Oz
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Re: fuel gauge sender needed

Post by Tony From West Oz » Fri 22 Dec, 2017 3:00 pm

Formula Ώ=ƥ L/A
where ƥ is the coefficient of resistance of the conductor,
L is the length of wire that you are calculating the resistance of and
A is the cross sectional area of the conductor.
Life is a journey, with problems to solve, lessons to learn, but most of all, experiences to enjoy.

'83 W123 300D 325000km (Wife's car Josephine - sold).
'84 W123 300D replaced good OM617 912 with OM617 952 and enjoyed having good acceleration for the first time since first driving a 300D in 2002 - became engine and trans donor for 300CD Turbodiesel conversion. Now parted out.
'86 W124 300D sold (Wife's old car - sold )
'85 W123 300CD, 275 000km (Fatmobile) rebuilt turbodiesel from previous Fatmobile transplanted into 280CE (occasional tourer)
'99 W202 C250 Turbodiesel (my darling Wife's car - Sold)
'98 W202 C250 Turbodiesel (my car - Sold)
'06 Ssanyong Musso Crew Cab 2WD Ute (OM662 diesel and Auto Transmission)

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