Hello everyone and thanks in advance for any thoughts on this problem which is starting to worry me. I have a 91 gmc 1500, 350SBC, summit CD ignotion box, and the gauge cluster from a '95 1500 So i could have a factory looking tach. I installed the DRAC behind the raido. So after a few months, all of a suddon, my speedo starts going crazy reading really high. If i were to turning on something that uses power, like the fan, AC, window swich, it would go back to normal. I didnt worry to much over it, but the more i drive it, the worse it gets. Now my tach is reading high, and anything above 40mph my speedo will real 85 (pegged out). If i give it a lot of gas, it will cut out a little bit. The main thing that has me worried now, is that when i try to use the cruse controll at any speed, it starts cutting out really bad, the truch starts jerking really bad, but when i turn it off it doesnt do it anymore. If anyone has any ideas please let me know

 

Check/replace the ground wires from the engine block to the frame and ground wires from frame to body.