I have found CB's to be less than ideally reliable. They are the first thing I look for if there is a circuit problem. To make matters worse, the later model C 150's have a hidden, self resetting CB for the alternator field. If it opens, and does not reclose, you have no charging, and no indication, unless your keen eye notes an ammeter discharge. ..
I attended a Cessna aging aircraft presentation many years ago. Cessna had bought back two 400 series Cessnas, both of which had had long and tough careers. The presenter told us that the deterioration of the structure they had expected to see, really was not too much a concern. In both cases, it was wiring, and electric components which were in horrible condition. Though Cessna has implemented structural SID inspections, the real message was to rewire the whole plane when it is aged. I guess this is why brand new Cessnas have better wiring, and many ground wires.
Pilots, know your electrical systems, so you are more able to diagnose, and assist the mechanic in finding the fault. "It doesn't work." will mean a larger repair bill, than a detailed description of the failure, and description of fault checking you have already done, and your observations.
When I have CB's removed, if I don't replace them, I at least measure the current at which they pop. I find it's often half again the rated value.