In another post (https://www.clublexus.com/forums/ls4...uel-gauge.html) I described the failed fuel level sender in my 1991 LS400. Sadly, there is no stock in the U.S. of the replacement part (83320-59045). I found one from a 1992 in the boneyard but it had exactly the same failure - the base wiper was worn out. On the chance that I might be able to make it work, I bought the sender from the next newer year series (83320-59065). Unfortunately, it is incompatible, having a different connector, a different float arm geometry and a different resistance range. It is, however, a much improved design in that it uses a coiled wire to make the connection from the wiper arm rather than a second set of wipers as on the earlier years.

Because the wiper itself was very close in dimensions, I decided to try to adapt it to my failed sender. The shaft diameter on both parts is the same (0.100") and the length of the wiper arm is perhaps 40-50 mils longer but within working range. The attached photos illustrate how the adaptation was made.

The first photo shows the two units with the older one being on the bottom. The second photo shows the internals of the wiper mechanism of the newer unit. Although you can't see the wire coil, you can see where the wire exits the box in the lower middle of the photo. The third photo shows how the two boxes compare. The newer one is slightly longer, preventing it from mating up to the older bracket. Note, too, that both ends of the resistor have connections versus only one end on the older one. The boss through which the float arm fits needed to be milled down to be about 0.100" shorter due to differences in the the wiper arm. Although I used a vertical mill to do this it could be accomplished with a Dremel tool since the wiper arm doesn't actually contact it.

The fourth photo shows how I mounted the wiper on the plate from the older unit. The wire bent easily and soldered well. The box has ribs that fit into the slots so I had to shave down the corresponding rib to account for the space taken up by the wire and solder. The last photo shows the wiper arm mounted in the box. In the photo, I'm using a 0.099 drill bit as a test axle.

After reassembling the unit and soldering the leads, a bench test showed solid resistance readings throughout the range. I've installed it in the tank so we'll see how it works in practice.

 

Good job! How did it respond to the repairs?

 

So far, it's working as expected. It'll be another week or so until the tank gets close to empty to confirm that it is working throughout the range.

 

Nice work! Thanks for sharing that. I read through your careful troubleshooting experiments and engineering a nice solution here. Very interesting.

 

I'm happy to report that the sender has been cycled through two tanks of fuel now and appears to be working perfectly.