I'm desperately hoping someone may be able to help with this as it's looking prohibitively expensive to get someone to come out and this is beyond this lady's DIY skills. My home has an old oil boiler with forced hot water for heating and an indirect water heater for hot water. The forced hot water has two zones. The hot water is working perfectly. Zone 2 is working perfectly. But whenever Zone 1 calls for heat, the circulator relay on the aquastat begins chattering. The boiler fires up and heat IS circulated (I can feel the baseboards warming up), but the chattering continues the entire time that zone has the boiler fired up. I posted previously thinking that the aquastat needs to be replaced, but now it seems like that may not be the issue. Any troubleshooting tips?