67Dart273 said

I finally dug through the junk box, went down to Radio Shack, and built myself a copy of the Mopar C-3826 guage test tool. It's a little crude, but hey, I'm not going to "show" it.

According to what I can find, the three test resistances for senders (in the C-3826 tool) are

L = 73.7 Ohms (empty)
M = 23.0 Ohms (1/2)
H = 10.2 Ohms (full

when the gauge is properly supplied by a working voltage limiter at 5V

The diagram:

Now Rad shack has a fairly limited supply of resistors, and I wanted to be sure and get enough wattage. That's the reason for the odd setup, as well as the switch

With the switch in "center off" for "cold" or "empty" the resistance of 73 ohms is all that is in the circuit. This is made up of a 50 ohm, (2) 10 ohm, and a 2.7 ohm I had in my junk box all in series.

With the switch to one side, the original 73 ohms is now paralleled with the proper resistance to make the combination work. So on one side I added (3) 100 ohm, which in parallel with the original 73, gives me 23.2 ohms for "1/2 tank" or middle of the gauge range

With the switch to the other side, I added (3) 33 ohm resistors in parallel, which once again are also in parallel with the 73 ohm combination, to give me 10 ohms for the "full" or "hot" reading.

The actual measured end results are 72.6, 23.2, and 10 ohms



A shot at the interior. Glued the resistors down with "GOOP." No it ain't pretty. Yes, it works

I think I left enough room to later install a 5V regulator so I can substitute that for a suspected bad instrument voltage limiter

Click to expand...