Lets do last question first. The 12 volt dash gauge is calibrated to work with a 12-volt sender which works in the range of 30-90 ohms. By contrast your original 6-volt sender worked in a range of 0-30 ohms. So if you change the dash gauge, you will also need to change the sender as well.

As for your temp gauge that is likely the same story. One alternative is to install a Runtz inline to each gauge. That way you can keep the original senders and dash gauges and everything will work as they did originally. Its kind of related to the kiss principle.....Thanks Randy

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