how do i repair valiant combi boiler hot water intermittent , central he ok?

ok i read alot of these forums there are so many shit engineers out there its unbelivable,
1stly does the hotwater run hot then cold ? and then possibly hot, if it does its a clogged or scaled up plated heat exchanger, the boiler reaches max temp due to bad circulation through plated exchanger, shuts off!. mains water through other half of exchanger cools temp, boiler fires up again so on and so forth. in badly clogged up plated heat exchangers. boiler will lock out on over heat, and u wont be able to reset untill temp has come down. another reason may bey a weak pump not able to circulate water quick enough to exchange heat with dhw inlet through plated heat exchanger, same symptoms as previous.its obvious its not diverter. as problems due to diverters are usualy rads getting hot when you turn hot tap on,(letby) boiler not firing up on dhw demand,and in the case of lots of early turbomax boilers the rubber ball and end of rod gets stuck in opening as it swells typically as valve is in dhw mode all summer. 80% of my breakdown work is sludged up systems that knacker pumps trvs aav,s. you want to save money in long run. get a trusted gas engineer to come once a year and clean drain and add inhibitor to your system, regards GASBOILERDOCTOR

gasboilerdoctor
November 2010

hai i fick s the new vaillant 831 is just come on 1 second then go off and gas markcome

james
June 2009

front bottom open cover catch. vaillant 824

euan
March 2009

what is the water sensor & how do i replace it

stu
July 2008

im corgi reg, the problem willl be for sure on your div valve, top up your system to 1.5 do not go over 2. if you need me to sort this problem out call 0845 8386 247 Universal Heating Ltd good luck pal. - Vikash Patel

vikash patel
June 2008

I has the same problem with my valiant turbomax 828E model. I got the diverter valve replaced with a brand new one and problem fixed.

P.Bates
May 2005

Having similar trouble with my Sime combi. I've been told it could either be low pressure in the system or the diverter valve. There will be a pressure gague on your unit and it should normally read about 1.5 bar. If your pressure is low look for the Domestic Water inlet pipe and follow that back away from your unit until you get to a small plastic tap which should be in a closed position. This tap will probably be the same type you would find on a washing machine cold/hot water inlet hose. Open it and keep an eye on the pressure. When you reach 1.5 bar close the tap. I can't give any advice on the diverter valve as I haven't tried that yet. Try ezypart.co.uk for parts. It also gives an explanaition of what the diverter valve does

Rab
December 2004