I get spark and pilot. Cleaned flame sense rod and no 24 volts to main valve . I don't have a meter that can read micro amps . Should the flame sense rod read 0 ohms from rod to connector. What out put voltage is the flame rod suppose to sink.. It reads 20 volts ac at the module .I read 4 volts at the flame rod ,but it restarts the igniter ... that was yesterday.,, Today I wiggled the flame rod connector at the module and main gas burners now work. I am replacing both module and pilot assembly that are 27 years old,but realize how little I really know about the electronic architecture of a any module.Since the boiler burners were submerged from a cellar flood I removed and cleaned every thing ,burners ,assembly ,etc. . The small amount of resistance from my meter prevented ignition, I wonder if it was only residual moisture. A good service tech would sell a new boiler ,but it is mine and it feels like I installed only yeaterday
Brian, I doubt that a responsible HVAC tech would undertake a DIY conversation with you regarding your issue. Your and your family's safety is best served by bringing in a professional, one who will, by his business insurance, assume the liability for the job and make a safe and correct repair.
Assuming all electrical connections are secure, the problem is most likely the controller module. I had the same issue a few years ago. By cleaning the flame sensor with fine emery paper, I got the furnace to limp along from November to February, then ended up wearing heavy clothing until the weather got warm. Further cleaning of the flame sensor proved fruitless. Eventually, I took a chance ($) and replaced the 20-year-old Honeywell controller with a new Honeywell unit, which restored normal operation, using the same old pilot burner and ignition electrode. An advantage of the newer Honeywell control module is built-in continuous self-testing and an LED that reports what is going on with a blink code.
