The International Cessna^® 170 Association

I have a 1953 C-170B. The needle portion of the T&B indicator is frozen. I think its electrical unit but can't tell. Any ideas on its power source?

It is likely* powered by a self-reset circuit breaker mounted beneath/behind the panel…which looks like a small1-inch round black bakelite hockey-puck. It usually also powers the stall warning. Check to see if your stall warning horn/light works…. if so, it’s probably not the C.B. (On the other-hand, if the T&B is internally-shorted …it may be de-activating/“popping” the C.B. …and if so, would prevent the stall Warning actuating also. In such case, if you electrically isolate/disconnect the T&B then, obviously, you can determine if it’s the C.B. or the T&B.)

* Some aircraft have been modified to utilize ordinary manually-resettable C.B.s.

Very good information. Thanks for sending me this. I'll pass on to my shop.