Fuel sender and grid heater problems

[Sandhiller]

My first problem is with the fuel sender. I took my pickup to a mechanic and he said that when he grounded it out at the tank the gauge would move. My low fuel light still works so I think its the sending unit. If someone on here know were to find one for the 89 year that would be great because I can find one for the 90s and new but not 89. I will use a 90s and newer if there is no difference in them.
My next problem is with my grid heater it will work if i un-plug the air temp sensor thing on the intake. It will also work normally if the temp is below 20 degrees Fahrenheit. I have to crank it a bit at below 35ish before it starts so I thinking it needs to come on around 35 not below 20.
I have also heard that the early 89s had a controller that made the grids come on at lower temps.

[Philip]

The 89's had a temp controller that was set to come on at 15 degrees. The 90 models went to around 50 degree kick on. You need a 90 model controller.

[thrashingcows]

As for the grid heaters....my 89 engine and harness in my crewcab would use the grid heaters, but just in short boosts to warm the incoming air. I never saw the actual "Wait to Start" light come on unless it was -15*C or colder.

I grabbed a grid heater controller from a early 91 truck and tired it with my 89 wiring, and it would come on like the 91.5-93 trucks. Anything colder then around 10*C and the "Wait to Start" light would come on.