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Modifying a Cycleguard (TLDR; you can't)
Like others I have the annoying Cycleguard LWCO on my boiler and the intermittent level test bothers me. There have been previous threads where people have speculated if it would be possible to modify it in some way to either eliminate this test or at least alter the timing parameters. Somebody even wrote to the company (and never received an answer I believe.)
I opened mine up and poked at the board myself, and unfortunately modifying it is not going to be something anyone without electronics and computer programming skill is going to be able to accomplish. The main control of the device is through a PIC microcontroller (12C508A) which is a one-time-programmable device (meaning you can program it once, but can't ever change that programming later...) Nor is it possible to extract the existing program from the chip. All the timing and state changes are controlled directly from this chip- the rest of the electronics on the board are for conditioning the logic signals into and out of the microcontroller for the sensors and relays.
If someone were skilled enough it would be trivial to develop a new program and replace the microcontroller (possibly even with a different device if desired- Arduino anyone?) The electrical design is pretty simple. The sense lines for the water level probe and "burner activation" input are conditioned into 5v signals and fed to the microcontroller's pins. Two other outputs from the controller run to relays for the burner power and water feeder. So with those 4 GPIO lines directly available it would be simple (for someone who knows microcontrollers) to replace the existing chip with something else.