Vaillant ecoTEC plus 837 Fault Codes

Dry fire.

Water shortage; the temperature difference between flow and return NTC is too large.

Water shortage; temperature rise too quick.

Interruption in the compact thermal module cable harness.

The appliance does not start: attempts to ignite during start failed.

The flame goes off during operation and subsequent ignition attempts fail.

Fan speed variation.

eBUS undervoltage.

Gas-valve control defective.

Gas-valve shutoff delay.

EEPROM error.

Electronics/NTC fault.

Flame detector input signal is outside the limits (0 or 5 V).

No valid DSN in the display and/or mainboard.

Flow and/or return NTC fault.

Water-pressure sensor signal out of range (too low).

Water-pressure sensor signal out of range (too high).

No pressure rise was detected when the pump was turned on.

Overheating protection on the primary heat exchanger has triggered.

Condensate pump or accessory feedback blocks heating.

Incorrect configuration with accessory.