The first thing to check is to ensure that the incoming water on the “right” side of the portable tankless water heater. If the incoming and outgoing are reversed, the portable tankless water heater will not work. The incoming is on the far right and the outgoing is in the middle.

Check to make sure you have fresh batteries and they are installed in the correct position.

Number one reason that the portable tankless water heater does not ignite is that there is not enough water pressure. You need a minimum of 0.25-10 PSI, sustained. Municipal water should supply enough water pressure. Most 12/18/120/240 pumps well as long as they are capable of delivering pressure of 0.25-10 PSI or greater.

A wire has become disconnected inside the portable tankless water heater during shipping. Make sure the gas is OFF. The front cover is held by six screws, four on top, two on bottom. The knobs pull off. All the wiring is done with push together plastic connectors. They are all visible without further dismantling of the portable tankless water heater. It should be obvious when a wire has become disconnected.

It is possible that some debris or epoxy might have entered the water regulator. Check to see if the filter screen on the water inlet is clear of debris. You can also reverse the hookup by taking your water source and hooking it up to the water outlet side and back flushing the system.

Propane gas cylinders sometimes are contaminated with air, especially new tanks upon their first filling. Cycle the portable tankless water heater turning off and on your output flow or similar. Does not include a shower head.