Pagoda SL Group

W113 Pagoda SL Group => Electrical and Instruments => Topic started by: 280sl1968 on September 30, 2013, 12:56:45

Title: Tank sender resistance wire
Post by: 280sl1968 on September 30, 2013, 12:56:45

I carelessly broke the thin resistance wire in my tank sender unit as I was cleaning it.

Things were going too well and my cleaning cloth got caught in it and it snapped.

Does anyone know the specification of the wire? I guess the resistance values are quite critical.

I'd like to resolder a new length of the right gauge wire if I can.


Thanks

David

Title: Re: Tank sender resistance wire
Post by: WRe on October 01, 2013, 05:51:41

Hi,
maybe you can find some info here: http://www.hanshehl.de/tipp19.htm
...WRe

Title: Re: Tank sender resistance wire
Post by: JosephBach on October 07, 2013, 00:08:29

i had tried this many of times, but to no avail. the readings were never accurate. ended up getting a used one...
however if you find a wire that works for you, please let me know!

Title: Re: Tank sender resistance wire
Post by: 280sl1968 on October 10, 2013, 17:21:44

The link provided by WRe is useful.

I did a bit of experimenting today with the broken wire from the sender to get some resistance specifications for a replacement.

I took resistance measurements over various lengths and the results were pretty linear:

1" = 7.5 ohm
2" = 15.1 ohm
3" = 22.6 ohm
4" = 30.1 ohm
5" = 37.6 ohm

So, it broadly came out at 7.5 ohm per inch, which extrapolates to 90 ohm per ft, or 295.3 ohm per m. These readings were taken in a cold garage - it was approx 12 - 15 degrees C.

Looking at the tables on various nichrome wire supplier websites, it looks like 41 gauge Nichrome 60 is a close match. This wire is said to have a resistance of 89.24 ohm per ft at 20 deg C / 68 deg F.

Now to find some......



David

Title: Re: Tank sender resistance wire
Post by: garymand on October 10, 2013, 17:45:28

You might want to buy a 100 or 50 ohm pot and substite it to see how the gauge responds and what resistance the gauge is calibrated to.  I've found the gauges have a hard time showing full scale / full tank accurately.  You could buy a few resistors to cover the range for the wire length and determine the best total resistance for the length to get full swing on the gauge.  Just a thought.  Fun project.

Title: Re: Tank sender resistance wire
Post by: WRe on October 11, 2013, 09:00:00

Hi,
to buy at Amazon or ebay UK,
e.g. http://www.ebay.co.uk/itm/100ft-30m-NICHROME-Nikrothal-41AWG-0-07mm-283-m-86-ft-Resistance-WIRE-/310704600536?pt=LH_DefaultDomain_0&hash=item48576ff5d8.
...WRe

Title: Re: Tank sender resistance wire
Post by: 280sl1968 on October 11, 2013, 10:21:29

Yes, I had seen that eBay listing - I just wasn't sure whether the resistance specifications were close enough.

I guess they are - I don't suppose the gauges are ever as accurate as one might think.

They have another reel of Nichrome 80 which is closer in terms of resistance values but it is $50 a reel.

Gary - the test resistor is a good idea. I have bought a used sender also and found that reads about 6.5 ohm full and about 65.6 ohm with the float at the bottom. When I connected this to the gauge and tested it dry (outside the tank) the needle seems to read OK, (ie at full with the float at the top and at the bottom when the float is at its lowest). These resistance figures differ to what is in the Technical Manual and those figures are quoted in Watts (an error I assume??).

Anyway, if and when I get new wire for the broken sender, I will report back with resistance numbers. It will be an interesting comparison.



David

Title: Re: Tank sender resistance wire
Post by: WRe on October 11, 2013, 11:21:57

Hi,
here you can find similar values: 6.8 full, 67.8 empty: http://www.beetle.homepage.t-online.de/Geber%20fuer%20Kraftstoffanzeige%20Pagode%20W113.htm
...WRe