I'm going to try and repair my fuel tank sender unit. Currently it's open circuit, so I probably need to replace the resistive windings and/or wiper, although this is speculation at present as I've not dismantled it yet. In order for me to source the correct wire, does anyone know the minimum and maximum resistance values for the unit please. If anyone has ever done this, please let us know how it went (good or bad!). Cheers.

 

Argh. My restorer has moved to Bloemfontein & we threw a couple of those away. All I have left is an Engine, Moss box & overdrive. The rest was sold as scrap metal. oops I'm sorry. Mine were S Type

 

I have both my S type senders out of the car (and out of the tanks). Just checked and the resistance... varies between 27 k Ohm to 250 k Ohm

 

25 to 250 ohms is the nominal values. I've never tried to repair on at the windings, but look at the terminals, you might be able to repair a break there. These resistance values carry on until at least Series III XJ, so you might be able to adapt another sender. I'll have to check, but I'm pretty sure the range changed on the later XJ40/X300 saloons. Those have plastic bodies instead of metal, so would be more difficult to work with.

 

Must be my eyesight reading the meter...didn't have my glasses on.. must have been 27 to 250 Ohms not k Ohms

 

Fabulous! Thank you all for your replies. Seems conclusive that these are the values I should be aiming for. I have absolutely no idea if I can fix it, but I always like to try as a first resort. I'll report back with my results. Thanks again.

 

VB, I think when you get in there, you will find it's the wiper that has worn, and/or the moveable contact that attaches to the wiper has failed.
There are different arrangements sometime there is a braded wire that moves, or it may have a simple contact on the bearing.
The bearing has become oxidized or it self is so worn that the slider has lost contact with the windings.

If the winding have become broken, they would be all frayed and making intermittent contact when checked with an ohm meter _ you would have readings all over the place when the slider was moved.

Look for a bad connection to the spade terminals through it's mounting plate as well.