Now my takagi tk3 finally lights up. Outdoor propane unit. It seems to refuse to light when the outdoor temp is at 40 degrees or lower, and the H2O and propane pipes are at 31-35 degrees or so. When the temp rises to 46-48 degrees on both gas and h20 pipes, it will light up eventually.
When the temp outside is 50 degrees or higher, it lights up.
Does anybody out there have any guidance for me on this system? The unit is not sooty, has all the condensation drain and dampers, has the 3/4" propane line from the tank, and the computer surge protector power strip. All the installation tips from the owners' manual have been installed and work ok. The big Rheem gas fired hvac unit on the same gas line works just fine. The overheat control fuse connector melted from white to brown, so I shunted it with a paperclip and the TK3 started right up. This is a white fuse wire wrapped around the back of the copper colored heat exchanger at the top of the unit, and the connector that melts goes between it and the hi-limit switch at the extreme upper left on the output pipe. This tip came from this forum. Thank you!