Gauge Issues on my CTD RC conversion

[pwerwagn]

I have a feeling that I am overlooking something majorly stupid, but sometimes you cant see the Forrest thru the trees right? On my 79 ramcharger/93 CTD conversion ( https://www.turbodieselregister.com/threads/234147-1-ton-Cummins-Ramcharger-Pop-Top-Build-Thread ), I used the 93 dash/wiring harness, etc in the 79 tub.

I also grafted the 93 fuel sending unit assy into the RC tank, and used all the stock wiring. I hoped it was all going to be plug and play since I didnt cut/splice/etc anything gauge related, but I have 2 or 3 minor issues that I cant quite figure out. I have not dropped the tank yet to check to see if the sending unit is good, so that is one possibility but I wanted to see if any of you have any suggestions of something obvious that I am missing.

All of the guages work, except the fuel gauge. Everything else electrical in the truck works (except the cruise...but Im not sure it worked before I did the conversion). Here's some gauge oddities I've noticed:

1) With the key off, the fuel gauge goes to ~1/4 tank, turn the key on and it goes to E.
2) When step on the brake pedal with the key OFF, the fuel gauge (and perhaps the temp gauge), slowly goes up the longer I hold the pedal.
3) If I turn the parking lights on with the key OFF, it does the same thing.

I very likely could have a pinched wire/wires running back to the tank/lights. I haven't ruled that out. I was just wondering if these symptoms are typical of a bad sending unit/bad gauge/corroded plug/etc?

Thanks!
Jeff

 

[B.G. Smith]

That is a printed circuit board in the dash isn't it? The fuel gauge is wired with 12v to one side and the wire to the sending unit on the other. The sending unit is a rheostat and the gauge reads the resistance at the sending unit. Sounds like instrument panel is not grounded? bg

 

[pwerwagn]

That was my initial thought. I checked grounds once, all seemed ok. I’ll check again.