[Yosemitest]

Sometimes at very busy airports, transponders within a certain range can overpower the radar and you get "ring-around" from the squawk (transmission of the code dialed in).
First the controller will ask the aircraft to "Squawk Low" to resolved the problem and if that doesn't work, he'll ask the aircraft to "Squawk Standby" (Par. 5-2-12.
Other problems can be a malfunction with the transponder that the Code transmitted is NOT the code being transmitted (which might belong to another aircraft in that area) and that would cause identification problems.
So the controller would tell the aircraft that "BEACON INTERROGATOR INOPERATIVE/MALFUNCTIONING. STOP SQUAWK." (Par. 5-2-15 and Par. 5-2-22.

Then there's electrical problems that might develop a fire, so the pilot would need to shut down, and MUST shut down the power to the transponder.

[FatherofFive]

Sometimes at very busy airports, transponders within a certain range can overpower the radar and you get "ring-around" from the squawk (transmission of the code dialed in).

That was my thought, could couse problems in airports. But why can they shut it down in flight?

[B4Ranch]

FatherofFive, are you at least going to say thanks for the detailed answer?

[FatherofFive]

Then there's electrical problems that might develop a fire, so the pilot would need to shut down, and MUST shut down the power to the transponder.

Thanks. But, does the pilot know there is a fire with the transponder, or electrical in general? If there is a fire in the electrical system, they need to shut down the electrical system. If they know there is a fire in the transponder, it should be shut down automatically.

It just seems to me that shutting down the transponder is a terrorist tool.