TST & speedo "jumping" code 0622

[ataboy9026]

My speedo has been "jumping" up 5-8 mph occasionally while driving since I installed my TST box. It happens at all speeds at different times. It will jump up or spike only for a second and return to correct speed. I called TST and they said there was no way it was their box as it doesn't have any trans control. But it does tap into a fuse the controls transmission. And this morning my check guages light came on with amp guage at zero. It is code 0622 - generator problem. I cleared code and started again, it ran with low volts for about a minute and tripped 0622 again. I cleared and tried again a few more times with the same results. So I bypassed the TST and it reads low for about 2 full minutes the comes up above 14 like normal. It reads low like it does when the grid heaters are on but the have never been on for 2 full minutes before. And its 50 degress out today. I drove it and the speedo does not jump anymore with the TST bypassed. Any clues???