I took the cluster out of my 65 Satellite over the winter to have the speedo fixed. Now both the temp and the fuel gauge only read halfway when the tank is full and the car is warmed up. I thought it might be the instrument voltage regulator so I swapped it out with another one I had, but no change. Any ideas?

make sure the mounting screws are grounding the printed circuit board & other than that confirm the continuity of all the connections in that area that you were working on

thanks Robert, the lights all work and the gauges get power to move halfway so I figured the cluster was getting a ground. I believe it grounds to the dash frame through the screws. Is there a way to run an additional ground to test?

you might touch a grounded jumper with alligator clips to the VL metal case & might just need a new VL (Murphys law). check that the VL is tight/secure (continuity)