Tom M'Guinn

Ok, if you need help on the temp gauge let me know. And good luck!

Baughbob

Success! I soldered the resistor back in place (2 places). I bench tested it and it worked perfectly. I put it back in the cluster and installed it back in the car and it works. I may need to tweak the 20 ohm resistor as my gauge shows half tank and the resistance on the sending point leads indicates about 5/8ths. On the right track. As for the water temp gauge, I bench tested it as well using my variable resistor and the resistances shown in Clarks Garage material. It seemed to track correctly. Upon reassembly, it was not working. I pulled the leads on the sensor and using my variable resistor set at 38.5 ohms, I connected to the sensor lead and ground. The gauge read 80C. I adjusted the variable resistor until the gauge read 100C and then checked the variable resistor. It read 14.5 ohms, some 24 ohms less. Any ideas?

Tom M'Guinn

Congrats of getting it working! Turn the trim pot all the way counter-clockwise to maximize the fuel gauge reading. If it's still low, then (a) you're in good company, (b) you might start be checking the resistance in the wire from the sensor to C on the gauge and cleaning everything in between to reduce the resistance (e.g., edge connector, sensor connector, football connector, etc.), and (c) if determined, you could probably "calibrate" the output by changing the value of that 70 ohm axial resistor. As for the temp gauge, just based on your results, it sounds like the gauge is seeing 25-30ohms more resistance than you actually have at the sensor. Again, that's likely being introduced in the edge connector or the football. A pink pencil eraser works well on edge connectors and under the football connectors, etc. Emery cloth or sandpaper works well too, but you have to be careful not to be too aggressive...

Baughbob

Early on, I had cleaned the edge connectors with a q-tip and electronic cleaner, along with the pink eraser. With my wiring diagram, I know which pin it is so I'll clean again. While out, I'll bench test the gauge again to confirm it is working as intended. I'll also check the resistance of the signal wire from the edge connector plug back to the sensor connector. I really appreciate the guidance.

Baughbob

Update, I adjusted the trim pot a bit counterclockwise and bench tested it successfully. As for the temp gauge, I did a better job of bench testing it and with my variable resistor set at 38.5 ohms (100C), my gauge is only reading 80C, or just slightly above. This corresponds with what I saw last night with the gauge connected and my resistor grounded at the temp sending unit plug. It appears that the additional 30 ohm bug is within the gauge itself. I checked the 68 ohm resistor that is soldered to the gauge. Unlike the fuel gauge where there was something visibly wrong, the temp gauge is not revealing anything. Any thoughts or guidance?