We have a boiler with a Taco circulator pump that was replaced 2 years ago, and the circulator pump recently stopped working. I realized this when two of the three radiators stopped warming up, and I realized I didn't hear any water running.
When the thermostat is on, the boiler turns on (fires) properly. There is a faint sound coming from the pump but it's rather quiet. I opened up the wiring compartment (behind a metal cover) and found that the capacitor is melted and discolored. So, that's a problem -- but I'm not sure if that's a cause or an effect of some other underlying problem.
Why would this happen, and should I start by replacing just the capacitor, or is it likely that I need to replace the entire pump?