Guages...must be a grounding issue, right?

[ddm156]

Still working on getting my guages working. Oil seems to be accurate, moves around from 40-70 as I drive.

Temp - always hangs at 120. Moves to that point after initial startup. I can run the truck and it never rises above 120. After running a while, I noticed from dropping something off once, if I shut the truck off for just 2-3 mins and fire up, the temp guage will rise up to around 170, then within about 30 seconds creeps back to 120. Almost like it reads accurate just at start up and already warm? I did run heat today and it blows warm air, and freshly replaced tstat with a tested (on my stove in a pot of water) and functioning 180 t Stat. When reading taken with ir thermometer was getting around 160-170 when warm. All this taken during freezing temps this morning...

Fuel- when truck is started it rises to empty. That's it. When I ground the sender at back of vehicle I get a full sweep to full.

I was thinking perhaps I had a stuck open tstat and a sunk float on my fuel sender (two seperate issues). Now im thinking its time to add some dedicated ground wiring to the cluster. Never had much trouble with this since rewire using centech harness in 07, but not sure what else makes sense and 9 out of 10 these issues with guages seem to be related to grounding issues...I also recently read on a thread here somewhere that a grounding issue in guage cluster may present in a degradation through the guages(did I understand that correctly)?

 

[Oldtimer]

Stock fuel, temp, oil gages are all the same electrically. They expect the sender to have a range of 10-73 ohms. Use 10, 27, and 73 ohm resistors to test the gages at mid range (27), and extreme ranges (10 & 73).

Edit: corrected mid range values

 

[Viperwolf1]

Mid range is around 27 ohms. It's a logarithmic scale.