I have a Weil Mclain CG boiler and it's behaving strangely. sometimes it runs a long cycle, sometimes a short cycle, and sometimes it fails to start. it seems like if the system is off for a while, then it will run a long cycle, almost like it needs to cool down before going again. typically, it runs one long cycle, turns off for a little while, then fails to ignite at all once or twice, then will short-cycle. it seems to be heating the house ok, but I'm worried it's going to fail when it's really cold.
I have eliminated these things as possible causes: ignition/pilot module, flue-gas spill switch, rollout fuse, 24V relay, thermostat, and thermostat wire (I can explain how I eliminated them, if you're interested). I removed the wiring harness from the damper, and shorted the interlock wire so that the system would run, and it didn't change anything, but I'm also not sure if the damper is working correctly, as it never seems to close.
I noticed the 24V relay was getting very hot, so I replaced it (only $20), but the new one is still getting hot while the system is running. so, I'm thinking it could be the ignition/sense control board, or maybe the gas valve. what is the best way to narrow it down from here? do you think I might have overlooked something? what other components might need to "cool down" before allowing a cycle? how would I test the water temp limit switch?
here is the wiring diagram for the system:https://i.stack.imgur.com/SJgjZ.png
is it normal for the piezo to click like it's trying to ignite at the end of a cycle?
I have some diagnostic skills, a multi-meter, and some experience doing AC/heatpump installation and repair. I'm fairly handy, and generally understand boilers, but I'm just not sure the best ways to diagnose. if you want, I can take some resistance measurements from the relay coil or other components to help narrow it down.
ohh, and the water temperature and pressure gauges seems to be reading reasonable values, though I'm not that experienced with hydronic/boiler systems.
edit: solution was the control board