Vaillant VCW GB 242 EH Boiler Problem.
Long One Sorry
Hello all,
Firstly I do have a little experience with gas, electrics and engineering, so not a total novice.
I have been having a problem with the hot water from my boiler. The problem started about a year after we moved to the property, the first year we were there, the boiler worked ok, CH and DHW worked fine separately and together. I make this point for background info, after about a year the hot water started to not get so hot and got worse until no hot water at all. I understand that this is one of the most complex boilers you can get, and also German, nuff said.
I read the other post on here about this problem, but ours is beyond that stage.
Called in a local random corgi engineer for a service and to fix the problem, he serviced the boiler (gave it a good clean), and thought the hot water problem could be the ‘water section’, he stripped the big round flat valve at the bottom, all cruddy inside, replaced it’s diaphragm and a little filter, think he used a repair kit, I am referring to the large valve at the bottom, the water section I think, (different engineers use different terms to refer to parts on the boiler randomly and interchangeably, which doesn’t help), I am trying to use the names from the boiler manual, which I now have for the boiler.
Anyway, this didn’t solve the problem of no hot water, he went away said he would check with a mate and give us a call. He phoned a couple of days later and said we would need a new heat exchanger, he could get one at 95 quid and fit it all in for 250. I said no thanks, after checking on the net and getting one for 55, 73 plus next day delivery, fitted myself easily.
Exit the first engineer having charged us 120 for the service and no fix, he didn’t have much experience so I wasn’t surprised, I’m now into 200 quid and no fix.
I being a bit handy (foolhardy), had a look at the operation of the boiler and could see that the ‘servo control valve’ wasn’t working, i.e. going round when you turned on a hot tap, and making the microswitch work, trip in the boiler etc.
My eureka moment, I duly ordered a new servo control valve, 45 quid and fitted and triumphantly turned my hot water tap, NO HOT WATER, central heating working fine. Thought I better get a professional in, Enter engineer no 2, 20 years experience, highly recommended, very optimistic at this point!
He phoned Vaillant several times whilst here and did a bit of diagnostic on it, decided it was the ‘differential valve’, (one that pushes in a pin on the main gas valve to fully let gas in) duly ordered and replaced, cost of 10 quid, still NO HOT WATER, (no high flame).
He phoned Vaillant again and they then said take off a tube at the back going into the combustion chamber and blow down it, softly first then hard, if flame profile increases when blown hard it’s definitely the ‘gas section operator servo’ on the main gas valve. Duly ordered and replaced by him 45 quid, STILL NO HOT WATER (no high flame)
Also new problem emerged, couldn’t have heating on as well as hot water, turning the hot water tap ‘cut out the heating’.
He couldn’t understand like me why this wasn’t now working after getting diagnostics from Vaillant, he went away said he would ask some mates and call back. In the mean time, the pump on the boiler failed and wouldn’t turn anymore, (woke up to freezing house) bought a new one, which was much smaller than the old one I might add 100 quid. STILL NO HOT WATER.
I had to chase engineer 2 up and he then said he thought it was the fan, a reasonable assumption , I thought, as the servo works on pressure from the combustion chamber. I phoned around, jokers told me 100 for the motor without the cowl etc. I took boiler apart and discovered the fan was on its way out, the bearing on the back of it was shot, barely turned when tested it out of the boiler. I thought I had found the problem, nah. I remembered I had a brand new boiler fan in my handy spares box, I duly fitted this, all working nice with a bit of sheet metal work to get it all sealed and nice. STILL NO HOT WATER. (no high flame)
I phoned my latest engineer back and told all about the fan etc, he explained to me how to adjust the screws on the ‘operator’, turn right screw to increase flame etc, not working, no increase in flame. He explained to me all about ‘soft light’ and modulation, he also measured the pressure with his manometer of the combustion chamber, and found that the boiler isn’t modulating between soft light and main flame.
The main gas valve is working ok, has been stripped and all fine, we can get higher flame by adjusting the ‘soft light’ flame with the left screw to get 50% flame increase, but I know this isn’t how it’s supposed to work, but this gets us hot water, YAY HOT WATER, but new problem NO HEATING when turn on hot tap, demand together is too much for the old girl!
Let this be a lesson to all you out there not phoning Vaillant at the start and being put off by their 200 standard fee!
Paid out on this boiler:
120 first engineer
73 new heat exchanger
100 new pump
45 gas control solenoid
45 servo control valve
10 actuator valve
(100) for a fan I luckily had and fitted
Best part of 500 squid and probably not needed half of it I bet!
Haven’t had the bill from the second engineer yet, he said ‘its beaten me’ on the phone to me on Friday.
Now my question is WTFCK is wrong with this bloody heap of scrap before I sledge hammer it off the wall, my wife is understandably incandescent, and threatening to leave, please help me save my sanity, marriage and be able to have a hot shower and a warm radiator please anybody help.
Any questions answered an the basis of a full understanding of the problem please.
To summarise:
Screw on right of servo control does not increase flame but left one does,
Boiler seems to stay in ‘soft light’ mode with green light on, on the control box
All airways, tubes have been checked to be clear
Followed diagnostic in manual, says to check control line banjo, is clear and fine
Says replace diaphragm pump, gas operator, both have been replaced and it still don’t work.
I have had a little look inside the back of the ‘control box’ at the bottom to check the pipes for free flow of air, as this seems where the problem is leading, all seems well, but what do I know right.
It is looking more and more to me like an electronics problem, but I havn’t got a clue how to test this or where to get new ‘boards’ from, could anybody with experience advise if we’ve missed anything obvious before we spend the cost of a new boiler on this piece of.
Any assistance much appreciated.
Long One Sorry
Hello all,
Firstly I do have a little experience with gas, electrics and engineering, so not a total novice.
I have been having a problem with the hot water from my boiler. The problem started about a year after we moved to the property, the first year we were there, the boiler worked ok, CH and DHW worked fine separately and together. I make this point for background info, after about a year the hot water started to not get so hot and got worse until no hot water at all. I understand that this is one of the most complex boilers you can get, and also German, nuff said.
I read the other post on here about this problem, but ours is beyond that stage.
Called in a local random corgi engineer for a service and to fix the problem, he serviced the boiler (gave it a good clean), and thought the hot water problem could be the ‘water section’, he stripped the big round flat valve at the bottom, all cruddy inside, replaced it’s diaphragm and a little filter, think he used a repair kit, I am referring to the large valve at the bottom, the water section I think, (different engineers use different terms to refer to parts on the boiler randomly and interchangeably, which doesn’t help), I am trying to use the names from the boiler manual, which I now have for the boiler.
Anyway, this didn’t solve the problem of no hot water, he went away said he would check with a mate and give us a call. He phoned a couple of days later and said we would need a new heat exchanger, he could get one at 95 quid and fit it all in for 250. I said no thanks, after checking on the net and getting one for 55, 73 plus next day delivery, fitted myself easily.
Exit the first engineer having charged us 120 for the service and no fix, he didn’t have much experience so I wasn’t surprised, I’m now into 200 quid and no fix.
I being a bit handy (foolhardy), had a look at the operation of the boiler and could see that the ‘servo control valve’ wasn’t working, i.e. going round when you turned on a hot tap, and making the microswitch work, trip in the boiler etc.
My eureka moment, I duly ordered a new servo control valve, 45 quid and fitted and triumphantly turned my hot water tap, NO HOT WATER, central heating working fine. Thought I better get a professional in, Enter engineer no 2, 20 years experience, highly recommended, very optimistic at this point!
He phoned Vaillant several times whilst here and did a bit of diagnostic on it, decided it was the ‘differential valve’, (one that pushes in a pin on the main gas valve to fully let gas in) duly ordered and replaced, cost of 10 quid, still NO HOT WATER, (no high flame).
He phoned Vaillant again and they then said take off a tube at the back going into the combustion chamber and blow down it, softly first then hard, if flame profile increases when blown hard it’s definitely the ‘gas section operator servo’ on the main gas valve. Duly ordered and replaced by him 45 quid, STILL NO HOT WATER (no high flame)
Also new problem emerged, couldn’t have heating on as well as hot water, turning the hot water tap ‘cut out the heating’.
He couldn’t understand like me why this wasn’t now working after getting diagnostics from Vaillant, he went away said he would ask some mates and call back. In the mean time, the pump on the boiler failed and wouldn’t turn anymore, (woke up to freezing house) bought a new one, which was much smaller than the old one I might add 100 quid. STILL NO HOT WATER.
I had to chase engineer 2 up and he then said he thought it was the fan, a reasonable assumption , I thought, as the servo works on pressure from the combustion chamber. I phoned around, jokers told me 100 for the motor without the cowl etc. I took boiler apart and discovered the fan was on its way out, the bearing on the back of it was shot, barely turned when tested it out of the boiler. I thought I had found the problem, nah. I remembered I had a brand new boiler fan in my handy spares box, I duly fitted this, all working nice with a bit of sheet metal work to get it all sealed and nice. STILL NO HOT WATER. (no high flame)
I phoned my latest engineer back and told all about the fan etc, he explained to me how to adjust the screws on the ‘operator’, turn right screw to increase flame etc, not working, no increase in flame. He explained to me all about ‘soft light’ and modulation, he also measured the pressure with his manometer of the combustion chamber, and found that the boiler isn’t modulating between soft light and main flame.
The main gas valve is working ok, has been stripped and all fine, we can get higher flame by adjusting the ‘soft light’ flame with the left screw to get 50% flame increase, but I know this isn’t how it’s supposed to work, but this gets us hot water, YAY HOT WATER, but new problem NO HEATING when turn on hot tap, demand together is too much for the old girl!
Let this be a lesson to all you out there not phoning Vaillant at the start and being put off by their 200 standard fee!
Paid out on this boiler:
120 first engineer
73 new heat exchanger
100 new pump
45 gas control solenoid
45 servo control valve
10 actuator valve
(100) for a fan I luckily had and fitted
Best part of 500 squid and probably not needed half of it I bet!
Haven’t had the bill from the second engineer yet, he said ‘its beaten me’ on the phone to me on Friday.
Now my question is WTFCK is wrong with this bloody heap of scrap before I sledge hammer it off the wall, my wife is understandably incandescent, and threatening to leave, please help me save my sanity, marriage and be able to have a hot shower and a warm radiator please anybody help.
Any questions answered an the basis of a full understanding of the problem please.
To summarise:
Screw on right of servo control does not increase flame but left one does,
Boiler seems to stay in ‘soft light’ mode with green light on, on the control box
All airways, tubes have been checked to be clear
Followed diagnostic in manual, says to check control line banjo, is clear and fine
Says replace diaphragm pump, gas operator, both have been replaced and it still don’t work.
I have had a little look inside the back of the ‘control box’ at the bottom to check the pipes for free flow of air, as this seems where the problem is leading, all seems well, but what do I know right.
It is looking more and more to me like an electronics problem, but I havn’t got a clue how to test this or where to get new ‘boards’ from, could anybody with experience advise if we’ve missed anything obvious before we spend the cost of a new boiler on this piece of.
Any assistance much appreciated.
