Anyone ever rebuild a gas gauge sending unit W114/W115 - PeachParts Mercedes-Benz Forum

meltedpanda · #1 11-10-2005, 08:34 PM

Removed my sending unit out of the ol gal tonight because it was not working. When I opened it up it was obvious why, old deposits made it impossible for the float to go up and down the arm within the tube and make contact with the top and bottom. It cleaned up nicely but alas the thin wires broke. has anyone successfully replaced these wires ?
or found the parts to rebuild?

meltedpanda · #2 11-11-2005, 10:02 AM

I decided to give it a whirl. I replaced all the wires and freed up the slider, Don't know if it will work but it was worth a try, new ones were $70
I just was not able to find the very thin wire, I used a strand of wire out of a 12g lenght

kpb · #3 11-11-2005, 10:30 AM

hi ron, necessity is the mother, right?

Tomguy · #4 11-11-2005, 10:41 AM

Were the wires you used insulated? The original ones might have been. I hope you don't find out if it should be insulated too late!

meltedpanda · #5 11-11-2005, 10:50 AM

Tomguy
no, at least they did not appear that way. There are three thin lines that act , as far as I can figure, like a rheostat as the float rises and falls, at its lowest point it contacts a copper disk that tells the low fuel light to illuminate on the dash. The lines run parallel to the shaft and integrate with some type of mechanism on the float. Not sure what or how that tells the fuel gauge how much gas is in the tank.

KPB, glad to hear you got the mail , stay tuned for further adventures!

250 Coupe · #6 11-12-2005, 03:22 PM

Ron,
I'm afraid it's not going to work. The wire is the sender has a higher resistance than ordinary wire. The span can be anywhere from 20 or 30 ohms to over 175 ohms.

The short length of 12 AWG you used will have a resistance of less than 1 ohm.

For more info, check out http://auto.howstuffworks.com/fuel-gauge.htm

Michael

psfred · #7 11-12-2005, 09:06 PM

That's fine resistance wire, I know of no source for it.

You will have to buy a new one.

We did the same thing on my brother's 300D --tried to clean the center shaft and broke one wire.

Turned out not to be corrosion, anyway, it's failed chrome plating, so it wasn't fixable in the end.

Peter

drewleroy · #8 11-13-2005, 03:49 AM

Resistance (Nichrome) wire is still widely used and is available from
http://www.wiretron.com/

I've only ever ordered copper magnet wire from them, and it was quite expensive. This route would likely cost more than just purchasing a new sender.

Drew

meltedpanda · #9 11-13-2005, 07:52 PM

Well you are all right, although I thought I was being pretty clever , and it looked really good, it did not work for the reason you gave 250 coup.
I am wondering if I used really fine wire , as in hair thin, for the two sending wires and the copper strand for the center if it would work?

250 Coupe · #10 11-14-2005, 01:33 PM

Ron,
The important thing is the resistance per foot. Altho very thin copper wire may have a slightly higher resistance, it will still be in the range of <1 ohm per foot.

The reason it's so thin on the sender is to give it better resolution (finer steps). You'll need to find wire that has the same resistance per foot and wind the same length to get a gauge that reads correctly.

Michael

billrei · #11 11-14-2005, 02:51 PM

I have a spool of 40 AWG Ni Chrome wire that I used to rebuild the sender in a 300TD I use to own. Rebuilding the sender is not easy because you need to tension the wire in order for it to work properly. If anyone wants to take a shot at repairing a unit I will mail you a couple of feet of wire. Just send me a self addressed and stamped envelope and I will enclose the wire for free. Private message me for my address.

anilv · #12 11-15-2005, 01:37 AM

What about yanking the sender off a W123? They're longer and should yield a suitable lenght of wire.. I would think one from a diesel is better as diesel should be less corrosive?

As for the resistance..I would imagine VDO used the same types of wire in all their sender and calibrate the readings at the gauge?

Anil