Common causes of flame and ignition failure in Tankless Water Heater and their prevention

Tankless water heaters with instantaneous heating always functions warm water on demand. As it is tankless, no water stays inside it. Instead, it warms the flowing water. It is an efficient water heater tool, but carelessness in its maintenance could down its efficiency.

Gas pressure or electrical input issue could be the main factor of flame and ignition failure in the tankless water heaters. Other common causes of flame and ignition failure lie and can be ruled out using simple routine maintenance practices.

Common causes of flame and ignition failure

The following are the common causes of flame and ignition failure.

The issue with Gas pressure or the main supply

The most basic factor behind flame and ignition failure is the uneven supply of gas or electricity. In case of ignition failure, there are two common problems;

  • The propane tank with no or less fuel
  • Working on the gas valve, either it is open or close

Similarly, flame failure is mainly caused by no or less supply of energy from the igniter because of an empty propane tank or poor working of the gas valve. Other major causes that do not allow flame production are;

  • Gas disconnection from the main because of the unpaid gas bill
  • Regulator failure that provides igniter the uneven gas pressure

More than one simultaneous demand

The overloading of the system causes flame and ignition failure by getting multiple demands at a time. When the system gets overloaded, it needs a flame to be ignited repeatedly without any pause. It will fail to work the flame and stop providing warm water on demand.

In this case, the overloaded system fails to ignite the flame even with a proper energy supply. This is because the igniter loses its igniting power and is no more able to produce a flame.

That’s why it is not wise to connect an instant heater with multiple water suppliers and should strictly be avoided to give multiple demands simultaneously.

Debris-containing flame scanner

The dusty flame scanner is just because of avoiding daily routine maintenance practices. Flame scanners always sense the energy provided to the heater to produce flame and manage to use the energy according to demand.

Daily air passage makes the scanner dirty, and the dust weakens its sensing power. Because of the low signaling power, a random energy supply without knowing the demand will affect flame production.

It is similar in case of ignition failure; the dirty scanner will lose its ignition power because of testing this situation, use another source of flame to check the ignition. If it is not working, it means the scanner failed both in igniting and producing flame.

Defective ignition cables & transformer

The more efficient the instant heater is, the more chances there are of its malfunctioning. The severe problems behind flame and ignition failure are defective cables and transformers that provide and transform the heat.

Ignition cables are the energy suppliers of the igniter of the water heater. The wear out or damaged cables will interrupt the electric power to reach the igniter. It will fail the igniter to produce the flame.

On the other hand, defective transformers are also caused by broken or cracked ignition cables. The transformer makes the heater defective in no time. It is because when it becomes defective, it does not transform supplying energy into heat and, in turn, causes flame and ignition failure.

Prevention of flame and ignition failure

Following are the preventive measures that could avoid flame and ignition failure by practicing them while maintaining the water heater daily.

·         Know codes for ignition failure

In the latest tankless water heaters, a self-diagnostic system is available. It comes with an LCD on the remote control or unit. If there is any problem with the flame or ignition of the heater, a code or light will appear on the LCD. It is like an early warning sign so you can check the heater and get it repaired before the issue worsens.

·         Protect heater from water and moisture

If you live in humid conditions, the moisture buildup on the heat exchanger of your water heater will cause corrosion. Due to this, the ignition will not work properly. You must keep checking your heater for any type of moisture buildup and remove it immediately to protect your heater from corrosion.

Moreover, corrosion can happen due to leakage in the heater. Inspect any signs of leakage and get it fixed. Also, check whether the tankless heater’s electrical connection and wiring are dry. If electrical connections are wet, ignition and flame will fail to start the heating system.

·         Check the wire connection and fuse.

Often the overheated fuse of the heater is damaged, which fails to ignite the spark. Check the fuse properly for any signs of damage and repair it. Another cause of flame and ignition failure is poor wire connection.

If the ignition wire has a loose connection strong spark will not be created, and a weak spark will keep jumping around. In such a situation, you should check whether the electrical wire connection of the ignition is properly secured or not.

·         Keep the vent clear

If there is any kind of blockage in the vents of your tankless water heater, the ignition will fail to start. To prevent flame and ignition failure, keep cleaning the vents by removing any kind of dirt or debris that may be stuck inside. Ensure that vent is performing properly so carbon buildup on the flame rod can be avoided.


Make sure that you take proper care of your tankless water heater. Even if you have the latest technology heaters, they can still undergo damage. Conduct regular inspections to find any signs of wear and tear, so you can get it fixed on time. If you cannot find the cause of ignition or flame failure, consult a plumber and get the issue resolved.

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