I have a 1998 GMC Diesel Mac Tool Truck that will not start. Engine type unknown. It started two weeks ago. Then about 10 days later if would not start. It initially acted like the battery was low which it was. It was charged but but still acted like a low battery. It clicked, and clicked. Then went dead. It would not charge. Both Batteries were replaced. Now there is no power to any circuit including starter switch, lights or alternator. Power from battery goes to a solenoid (no growing wire) under dash then branches (2 wires) to a point under dash. Can not trace further. My mechanic found with his tester that the fuse box does not have any power. Using his tester he could gave the fuse box power. All circuits would power up. Head lights came on, dash lights came on, glow plug came on, ignition switch turned starter over. Because it was only partial power all circuits went dead when power was removed. Auxillary batteries are charged and the lift gait works even with out motor running.

Replaced all battery cables including ground wires. Still no life. Checked for other loose wires, and faulty grounds.

Have not been able to find any wiring schematics.

Help. Any suggestions.

What chassis is the mac truck based off of? If we knew that it might help a little. i am guessing it could be a cummins or a Cat. i am ust guessing if a cummins it would be the 5.9 and it could be a bad wiring harness? same with cat, but if a cat it would be a 3126 same problem i would assume bad harness or a wire got cut on the frame causeing a short. but i am just stabbing in the dark here.

sounds like you got bad power connections somewhere. if your mechanic can supply power and everything works, then your grounds must be good. you really gotta know what chassis your workin on though.

There should be a vehicle VIN nameplate post all the info off of it and I will run the VIN.
CC

I have a 1998 GMC Diesel Mac Tool Truck that will not start. Engine type unknown. It started two weeks ago. Then about 10 days later if would not start. It initially acted like the battery was low which it was. It was charged but but still acted like a low battery. It clicked, and clicked. Then went dead. It would not charge. Both Batteries were replaced. Now there is no power to any circuit including starter switch, lights or alternator. Power from battery goes to a solenoid (no growing wire) under dash then branches (2 wires) to a point under dash. Can not trace further. My mechanic found with his tester that the fuse box does not have any power. Using his tester he could gave the fuse box power. All circuits would power up. Head lights came on, dash lights came on, glow plug came on, ignition switch turned starter over. Because it was only partial power all circuits went dead when power was removed. Auxillary batteries are charged and the lift gait works even with out motor running.

Replaced all battery cables including ground wires. Still no life. Checked for other loose wires, and faulty grounds.

Have not been able to find any wiring schematics.

Help. Any suggestions.

sounds to us like you are running a grumman style truck, in which case it is a 6.5l... sounds like you are not getting a good connection on your starter main wire... this is where all power is distributed from for all other systems except your lift... check the pin on the starter, it could have been over tightened and bust inside... if the starter is burned out it can short internally..... you should start here, as this is the problem area most of the time....the 2 wires that were traced back are probably a manual glow plug controller..:)