ltoolio

I cracked open (not literally) my fuel sender and the three wires are all snapped.

I'm considering trying to resolder new wires, but before I potentially go waste some....anyone else do this already?

Speedtoys

If they can be soldered..why not? Its a horribly simple circuit.

AirtekHVAC

I did it....it did not work. I used conductive solder, with copper tin contacts on the end....it did not register....wasted my time....your mileage might vary.

jpitman2

Cant hurt to try, now you are this far in. My gauge was erratic, but wires were not broken, and after cleaning the shellac like deposit off them it works pretty well now. The wiper contacts are bent metal like >, and one of mine had the wire on the open side, inside of sliding on the point. The resistance on mine varies from close to zero up to ~ 80 ohms
jp 83 Euro S AT 57k

ltoolio

Since we have some different opinions here, I'll give it a shot and report back.

G.P.

AFAIK the wires have a built in resistance, they are not a normal conductor.
If you managed to do a very smooth solder joint so the float level switch will slide over it, you would still be changing the resistance of the 'loop' of wire in the sender by spreading solder onto the wire. I'm not sure how much of an effect this would have on the accuracy of the fuel gauge.

The following is from a post on another site I made a couple of years ago when trying to sort out my fuel gauge-
The difference between the up to 1988 and 89+ senders appears to be the length of the resistive wires and therefore the travel of the float, the 89+ sender is about 10mm longer. You can see this when the outer sleeve of the sender is removed. I had a total resistance when empty of 70 ohms on the up to 88 sender and 77 ohms on the 89+ sender. The other obvious difference is there are three connections on the up to 88 and only two on the 89+. If you want to repair a sender with a broken wire, I think the gauge is 43 Swg or .09mm.

jpitman2

All conductors have some resistance, its just very low in most 'normal' wiring. As the wire section gets thinner, the resistance will go up.These wires seem to run 35-40 ohms each , at less than a foot long.
Nichrome 80 is 26 Ohms/ft in 36 swg so its in the ballpark.
Do the 89+ models not have a low fuel warning, or do they do it differently than the early models?
jp 83 Euro S AT 57k

9two8

I soldered mine 4 years ago, and it still works fine .


Ken
80 928 S
5 Speed

UK

G.P.

The 89+ models only have 2 wires. The low fuel warning is done via the electronics in the dash, AFAIK. My low fuel light at the gauge comes on when there is about 15 liters left in the tank. There is a printed message in red on the digital part of the dash when the fuel is low also, but I have not seen this on mine since I got the fuel gauge working. I could mess around with the 3 wire pre 89 sender and probably get the digital warning working, but I'm happy with the way things are working now.

jpitman2

The low fuel warning is SHOWN on the dash in all cases, but in 89+ where is the signal that its low coming from? Is only one wire used for the level, the other for low level? Do the electronics deduce the fuel is low by adding up the fuel used, or from the gauge reading?
jp 83 Euro S AT 57k

The Forgotten On

89+ fuel level warning is done by the gauge cluster as stated above. It has no separate circuit like the earlier units.

Porsche outlined how to set it when installing a new sender in section 20-19 or the WSM.

You basically tell the dash when to show the warning based on the resistance from the sender unit when it has 15 liters of fuel in the tank.