You have a weak ground. Run a ground wire from your tripac engine block directly to the negative side of the battery and should solve this problem.
It's a bad ground. Take top cover off and hook a #1 or #2 awg jumper cable to the tripac engine block and run it to the truck alternator...
It's your engine ground. Hook a #1 or #2 awg jumper cable up aywhere on your tripac engine block and run it up to your semi truck alternator...
