hi,i am looking for some help i have a vaillant 242 boiler and the hot water as been going off for days at a time then will just come back on,its gone off again,central heating great,just no hot water, no indicator lighting up on display panel and no ignition from burners,i have pushed down the micro switch with water running and indicator light comes on and the heater burners ignite but no hot water from taps,not sure how long it should take for water to run hot through taps? i am not sure if this is the problem (microswitch) or could it be something else? any help in this matter would be appreciated.

jimbo, September 2007

Who do I put micro switch lever

Naz, September 2012

Sorry to threadjack this older post, but I noticed you mention the little white plastic lever braking.

I think this has happened on my turbomax. I've already overhauled the valve once a few years ago to replace the diaphragm. I've done that, but I can see the white lever is also dead.

Can I buy the lever on it's own or in a smaller kit or do I have to go for the full valve service kit? Vaillant 140352

I can pick that up at parts centre which is neat, but it's kind of expensive.

John, April 2009

I have had the same problem several times, You say you have replaced the microswitch, have you looked to check if the small white plastic lever that comes out of your diverter valve is moving up and down to operate the switch if so then make sure its set in the correct position to switch the switch.

If it is have you tried replacing the dhw diaphragm? this is done by switching the boiler off, draining it and then you remove the white cover on the very bottom of the boiler and look up. You will see 6 brass screws, on the bottom of the brass diverter valve along with a nut and a screwed thread. Using a good philips screw driver undo the 6 brass screws. You will then see the diaphragm. Remove the diaphragm and check to see if its holed if so then replace it. If its ok then it sounds like its the diverter valve stuck.

Mine has stuck twice and the diaphragm has been ok each time. My experience why this sticks is because the diverter valve is like a small needle valve that is chromed and over the summer whilst the heating is not used the valve remains in one position and the chrome is damaged in a minute spot causing it to jam when the heating is switched on.

You have two options, 1 - replaced the diverter valve but this is expensive and usually not required. The other is buy a kit from Wolseley Parts Center (Parts center No. 475669, Vaillant number 14 0352) this kit contains everything you need to overhaul your diverter valve and the job is "doable" if you have any mechanical confidence. You will need to strip the valve down and replace all the component parts and grease the o-rings with the silicone grease provided and rebuild and replace it. To remove the diverter valve though you will first have to remove the pump.

One thing to remember though depressuirze, drain and isolate your system electrically first as this will prevent any unwanted water damaging any sensitive electrical components.

Hope this helps Steve

Steve, October 2007

I have had the same problem several times, You say you have replaced the microswitch, have you looked to check if the small white plastic lever that comes out of your diverter valve is moving up and down to operate the switch if so then make sure its set in the correct position to switch the switch.

If it is have you tried replacing the dhw diaphragm? this is done by switching the boiler off, draining it and then you remove the white cover on the very bottom of the boiler and look up. You will see 6 brass screws, on the bottom of the brass diverter valve along with a nut and a screwed thread. Using a good philips screw driver undo the 6 brass screws. You will then see the diaphragm. Remove the diaphragm and check to see if its holed if so then replace it. If its ok then it sounds like its the diverter valve stuck.

Mine has stuck twice and the diaphragm has been ok each time. My experience why this sticks is because the diverter valve is like a small needle valve that is chromed and over the summer whilst the heating is not used the valve remains in one position and the chrome is damaged in a minute spot causing it to jam when the heating is switched on.

You have two options, 1 - replaced the diverter valve but this is expensive and usually not required. The other is buy a kit from Wolseley Parts Center (Parts center No. 475669, Vaillant number 14 0352) this kit contains everything you need to overhaul your diverter valve and the job is "doable" if you have any mechanical confidence. You will need to strip the valve down and replace all the component parts and grease the o-rings with the silicone grease provided and rebuild and replace it. To remove the diverter valve though you will first have to remove the pump.

One thing to remember though depressuirze, drain and isolate your system electrically first as this will prevent any unwanted water damaging any sensitive electrical components.

Hope this helps Steve

Steve, October 2007

email me if still having trouble
dpmartin17@aol.com

paul martin, October 2007

dhw diaphragm or plastic lever broke in diverter valve. vaillant do a full service kit

paul martin, October 2007

hi me again,i have replaced the microswitch but still no difference,c/h working no problem,microswitch working when push it down but what operates the microswitch because it just not working off the taps been switched on?
checked heat exchanger the domestic hot water pipe cold running from it,help please what else could be stopping the hot water.thanks

jimbo, October 2007