it's not 'shorting', that would be arcing and sparking .... when the gauge gets power it's default position is pegged full until the resistance from the sender gives it a ground - check your sender wire again, and the sender itself, as well as the ground to the frame with an ohmeter, unless you find a resistance between 1 [empty] and 30 some [full] ohms you have an open circuit. if the sender and wire check good you have a bad gauge
Bill
