Help! Fault with Vaillant837

[Nicholas]

This fault code generally relates to a faulty circuit board on the boiler and you will need to replace the circuit board.

Vaillaint produce a circuit board to fit all of their boilers and you would need to program the circuit board to tell it which boiler it is installed within. After removing the front cover, pull the circuit box down on the front and undo the clips but secure the front panel. You can pull these clips up with your finger to release them. This will give you access to the main circuit board. Take a picture with you phone of the circuit board with all the wires connected. Ensure the electrical supply to the boiler is fully isolated and using a multimeter, check that there is no voltage to the boiler. You could also use a contactless voltage detector to ensure the boiler is isolated from the electric supply.

Pull off the connect to the circuit board and remove the old circuit board. Reinstall the connectors as they were before and put the cover panel back on. Pull the control box back up to the front of the boiler where two clips on the side will hold it in position and reestablish power.

The boiler will come up with a fault F70 which basically means “I need to know what boiler I am installed within”. On old models pre 2012 you will need to hold the information and reset button and then use the plus button to come to D97. Then press the information button and the plus button in number 17. This will allow you to go into the installer level and in this level you need to go to D93 and install the item specific code for the 837.

This should be in instructions for the circuit board.

If the boiler is an after 2012 model with the LCD display you will need to press the Two information buttons at the top and using the plus or minus button bring the cursor down to installer level. Where it will say installer level press the right hand information button increase the number to 17 hold the right hand information button and this will put you into the installer level. You will then need to use the plus and minus to go to the diagnostic level. Once here press the right hand information button and again go to D93 where again you will need to put in the item specific number to tell the circuit board what boiler it is in.

For after 2012 onwards the item specific number is 17.

For before 2005- 2012 the item specific number is 8.

[Paul Williams]

Cheers Nicholas, this is very helpful.

It is a newer after 2012 model, so I will try your suggestions.