That gauge cluster looks great. Do you have a picture of the completed face? Real tedious work but great job!
Thanks!
Over the winter break I made a calibration box to get the needles on the right way. I found the values on-line for what the gauges should be reading.
For Truck Years: 1979 - 1990
The Temp Gauge Needle Should Point to:
Left Line (Cold) when sender resistance = 1,365 Ω
Middle Line when sender resistance = 96 Ω
Right Line (Hot) when sender resistance = 55 Ω
'87 FSM Electrical Diagnosis Service Manual Supplement:
Oil Pressure Sender:
90-ohm at max pressure
0-ohm with no pressure
Fuel Gauge Sender:
0-ohm at empty
90-ohm at full
From this it looks like the temp sender is logarithmic. I think the oil and fuel senders are linear. I made a calibration box with parts I had on-hand. Unfortunately I didn’t have the exact value pots so I put a resistor in parallel on each. This made their sweep logarithmic. Double unfortunately the pots that I had closest to what I needed have detents so I was unable to get an exact adjustment to the values I wanted. They are close enough. The calibration box has an input from a power supply, three pots for the three gauges, and a wiring harness to my cluster. I measured with an ohm meter to get close to the center values of Temp: 96 Ω, Oil: 45 Ω, and Fuel: 45 Ω. I then attached to power supply and gauge cluster. With 12v input I attached the needles at the center position. I tested at 14v and 9v, and swept through the range of each sender. I adjusted the needles as needed. Unfortunately the oil and temp movements were reverse since I’m using the gauges upside down. I spent a few days learning about gauges and playing around with trying to modify the windings to reverse the movement. In the end swapping the two gauges worked, a simple solution. I have yet to install the cluster in my truck and I may try to modify the needle balance as the needles drop when not energized.
