[sunman]

#4 wire is rated at 85 amps max. Are you pulling power from alt terminal or starter? You are pulling 80 or more. Your alt can put out 185. When amps go up volts go down. That happens when your #4 carry’s more than 85. You probably have a fuel prob or something else but you really need to be on switched side of disconnect. I think it’s a rule. Check out the thread above this one about disconnects