Gauges 1966 temp/gas part missing

! Thank you !
There were condensers as well as voltage regulators.
And, some year around there the regulator was inside one of the gauges, and the condenser was screwed to the back of the cluster.

If you are asking about the little canister with the wire, that is the condenser.
Condensers are for limiting RF noise and for the most part only affected AM radios, and it can be left off with little to no noticeable difference at all except for needing a spacer for the tab on the condenser wire where the regulator plugs in together with it.

Here's a generic 66 Dart panel back showing both.

oldregout.jpg