How do I light pilot on Vaillant boiler - Water Heaters

You need to replace the thermal couplerhttps://youtu.be/jDvo4yJ1OdE

There is a thermocouple heat detecter in the pilot flame clean it 240 sand paper is ok. replace if not working.

We have just had our old system boiler replaced with a vaillant ecotec plus 837 and sounds like a similar working operation to ours. At first I was a little concerned,but I was told by our installer that he was told by vaillant that these very latest boilers size the system on start up for about 10 mins, then take temperature to target flow which you set boiler at. So even by setting target flow temperature very high you still get the initial sizing cycle, which ours was about 30-35c temp. These boilers seem to run biased for efficiency as after a while they modulate the boiler burner down and the radiators run more on the side of warm than really hot like the old type boilers. You also get better efficiency as at lower temperature the boiler condenses better. You will also find you get a more constant temperature in your home rather than over shoots. I was concerned at first, shame there was no info/explanation in user manual as people do need to know that this is normal operation. We are used to ours now, took a month and by the way these boilers can make a creaking noise but was told this normal expansion/ contraction but annoying when sited in bedroom cupboard. Best of luck!

Check out the vaillant web site Or talk to there hotline people .

According to the user's guide, the fault code means that the boiler failed to start after 5 attempts. Here is the manual where I got the information. I would confirm the codes with your particular model. I am presuming that the codes would be standard for all their models. Source(s): http://www.vaillant.co.uk/stepone2/data/…

refere to manual check for override switch loss of pressure no problem re-pressurise and check for leak top of rad valve good place to start

check to see the time clock is set with the clock symbol. there are three settings on analog clocks I , O and clock the I setting is constant running, the O setting is off and the clock setting is timer.
also try setting the thermostat up higher to see if the boiler fires.

it also sounds as though the pilot injector could be blocked so when the boiler comes on it extinguishes the pilot & then when the burner goes off boiler shuts down, or also the pilot rate maynot be set right, so when the main burner kicks in it robs the pilot of the gas it requires.
It could be that, or there is lack of ventilation for the boiler, so you get flame lift off when the boiler fires?

more likely the thermal coupling is u/s get new one fitted

TAKE A SHPO VAC AND CLEAN AREA. MAKE SURE YOU PAY SPECIAL ATT. TO THE PILOT LIGHT. FIND BUTTON HOLD IN AND IGNITE DONT LET GO WHEN IT LIGHTS FOR AT LEAST FIFTEEN SEC.. YOU MIGHT ALSO HAVE TO TURN THE THERMASTAT OR KNOB TO PILOT FIRST. AFTER IT HAS LIT TURN UP FLAME