I have an Armstrong Astro 25BS recirculating pump that has quit working. It is about 5 years old. There is some kind of capacitor or something connected in the box. Is there a way to tell if the pump itself is bad?

Hi,
The most common problem with these circulators is that the stator gets stuck and does not turn.
Sometimes you can take out the four bolts on the corners and pull the motor off. Get the stator freed up again and it will work. Make sure to turn the water off before dissassembling the pump. Hopefully you have valves do you can isolate the pump.
Also check that the impeller has not broken off the end of the shaft, that also happens sometimes.
You can check the cap. with an OHM meter by switching the terminals with the test leads and the resistance should count down to zero with each switch of the leads on the terminals...if not it is bad, but replacement of the cap. may not fix the pump usually it is a secondary failure...
If you can't get the pump ot work after taking it apart and making sure it turns freely then I would replace the pump.

Heatman101