Purney,
The heavy wire you are describing (10 gauge) that comes from the starter should go into the cab and attach to the positive side of the ammeter. The coil wire (+) shouldn't and probably isn't spliced into that big wire! It might appear it is spliced into the heavy wire, but is actually taped along side of it in the loom and goes into the cab to be attached to the key switch.
It would not function if it were spliced into the heavy wire...actually it would work, for a couple of hours!
Stuart
