anything is possible aftermarket, did you buy new gauges?
if the tamp gauge is electrical, than it should be fine on 12V, but the original would have been mechanical, although some folks mistake the small tube for a wire, especially if it's been cut when removing the gauge .... nothing has to be changed, the electrical senders provide a resistance, but for a 6V gauge to read correctly with higher voltage a "runtz resistor" needs to be added inline, they're available at most of the vendors
Bill
