Vaillant Turbomax Plus - destroying gas valves..

Hi All,

Wonder if anyone could shed any light on the following problem.

I bought a house a couple of years ago which came with a Vaillant Turbomax Plus fitted, a few months after I moved in the boiler stopped igniting, and a BG engineer came out and told me that the boiler was irrepairable due to its age, and that I should replace it with a lovely new one (to be fitted by BG).

I wasn't too keen on this, and shortly afterwards discovered that a friends brother is a central heating engineer, and he offered to take a look. He immediately diagnosed a faulty gas valve, and replaced it at a cost of £90. Nine months later the same fault occurred, and he came back and changed the gas valve again - at no cost. Now (6 months later) the gas valve has failed again, and again has been replaced for free.

I've talked to the central heating engineer who's been doing the work, and his view is that the valves are probably faulty (apparently the current parts he's getting are made by a manufacturer he doesn't trust), but he's reluctant to look any further into the problem as long as his supplier is willing to keep on replacing the knackered valves.

My question is, is there anything else that's likely to cause recurrent failure of the gas valve?, - my thinking is, that if, for example it is likely that a faulty PCB could cause this, then I'll keep my eyes peeled for a cheap 2nd hand replacement for him to install next time the gas valve dies. Incidentally, he did phone Vaillant's technical support people the last time this happened, but they were pretty useless, and basically recommended changing every conceivable part and seeing what happened.

If the gas valve in your boiler is a Honeywell, it is likely to be the gas valve lead

These have a diode in them that fails and takes out the gas valve and often the pcb as well.

BTW all you Vaillant haters also a problem when I was with Baxi/Potterton.
I'd imagine this was with all boilers usung this gas valve and lead

is the gas valve failing or is there shale from the gas pipework blocking the filter, just a thought!

Could b shale in the filter but valves don't fail that often,,which one is it does it have a grey cap held on with posidrive screw or is it a sit valve with a clear plastic cap,,, there were 2 types on this model but is he fitting new valves ? No disrespect but if it's honeywell 053473 they r £96+ vat trade £130+ vat retail Lol!!

I suspect there is more to this than meets the eye!

Nor have we been advised of the failure mode!

The all in price of £90 seems far to cheap. My rampant brain wonders if he is actually employed by a fair and nicking their valves!

I am not sure of the configuration of the PCB or gas valves. Some are fed with AC and other with raw DC. Some have bridge rectifiers built into the gas valve lead ( of which a batch mostly failed to the point that Potty rad out of leads! ).

Whenever I encounter a fault I try to assertain exactly what has failed and why!

Its possible a single diode on the bridge has failed and is applying part AC and part DC to te valve solenoid. A scope would be an easy way to check this.

I dont recommend 2nd hand PCBs. They are probablematic enough when new and buying used from Ebay are likely to have been removed because of intermitttent faults etc.

Tony