the ammeter should be wired in series with all the power the truck uses except for the current going to the starter motor itself. for negative ground vehicles, the positive lead from the battery goes to the starter (or solenoid). do not disturb that wire. from there the current is routed to the rest of the vehicle. it is in this lead that the ammeter should be inserted, that is this wire should be interrupted by the ammeter as it is common to all current drawn except for the starter. so this wire should go from the starter/solenoid terminal to the + terminal of the ammeter, then from the - terminal of the ammeter to wherever the interrupted lead went before the ammeter was added.
