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?

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1 Answer 1


It's possible the capacitor simply failed and compared to the cost of the entire pump, quite inexpensive.

As a first step, I would try replacing the capacitor with one that is rated for the conditions. I can see -40-+90C on it. That may not be adequate for this application. You might also see if you can get a higher temperature rated capacitor as a replacement.

  • Replacing the cap fixed it
    – Kulluk007
    Dec 5, 2021 at 18:50

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