I have a Navien N240-A-LP tankless water heater. Will not stay on.

SOURCE: rheem tankless water heater wont lite

the system was not sized properly, you need to have a 3/4 gas line to the unit for the volume of gas it needs, the tankless water heaters need to have every bit of gas that is says, it sounds like who ever installed di not make sure you had enough gas comming in the house, you might have to either have a new meter installed or run the gas lind directly from the meter to the water heater and cap off the gas line thats there

SOURCE: what is error code 59 on a noritz tankless water

The 59 code is typically caused by insufficient gas supply to the unit. It can also be caused by obstructed exhaust flow, stuck exhaust damper (located directly on top of the unit's exhaust), insufficient makeup air, or improperly installed venting (i.e. too long or too many elbows).

I would recommend initially checking the incoming gas pressure at the gas connection on the unit. The gas pressure should not drop below 5" water column for a natural gas unit, 8" for a propane system (the unit need to be operating at its maximum output).

SOURCE: My Paloma tankless water heater flashes C2 11 error code

I just had the same problem and I fixed it in about an hour or 2. First shut off the gas,water and power(unplug it) Take off the cover There are about 20 screws above the electrical circuit board. You have to remove all of those screws to remove plate that is covering the burner assembly. The burner assembly has these 3 pins that look like number 7's these are covered with build up and gas can't flow right. That's why you get the c211 error not enough gas. Take a wire brush and gently remove any build up, I also cleaned the thermocoupler which is next to the burners. It looks like a metal pin with a couple of wires coming out of it this was also very dirty. I took a can of air and basically freshened it up It works perfect now. Email me with any Q's at [email protected] Good Luck All that you need is a long phillips screw drive and a drill because its about 25 screws
The burner assembly has 2 screws all the in back underneath the assembly once you remove those 2 the assembly comes out . You don't have to disconnect any wires.

SOURCE: Paloma tankless, gas, water heater, error code C7 76

If you look on the left hand side of the burner control module you'll see 4 capacitors - the capacitors have most likely failed...pretty sure anything code 76 is P/S failure. It may also be covered for manufactures defects. If the cap is blown..the top will be slightly raised as apposed to flat like the other nearby caps - they are called top blow capacitors...the damage should be evident.

SOURCE: richman gas lp tankless hot water heater. used for

I had the same problem with my Paloma a year and a half after installation...contacted Rheem\Paloma\Richman customer service (800-432-8373) and they recommened a local installer in my area. The technican diagnosed the problem as the "flow control valve"; he managed to get Rheem/Paloma to cover the part under warranty...I only had to shell out the money for the install.