Bloody boiler gas valve (I think)!

No idea about your particular boiler, but on my MAN Micromat (with an Eco Hometec badge on the front) you can indeed replace just the solenoid coils - that's exactly what the repair man did last time it went wrong. Have a good look at it - I think they just pull off on mine - maybe after removing a screw.

Regards, Simon.

Tried giving it a gentle tap with a hammer it might just be stuck. How ever open circuit is not a good sign that percusive maintenance will do anything useful.

No back up heat sources? Tut tut...

Got a halogen heater, keeps me warm, but not much else.

I think its definately the solenoids have shorted, when testing between the red & black wires I get a voltage in excess of 250v dc.

So, can the solenoids be replaced, or does it have to be the entire valve ?

Solenoid is not available as a separate part it would have to be a complete gas valve.

However, you would probably end up with a new boiler and empty pockets if you just keep swapping parts.

Go here

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In message , "Simon (Dark Angel)" writes

Open circuit ?

If your gas valve solenoid (s) has gone, all you can do is wait until the shops open and get a new valve

I don't think you can just swap solenoids

In message , "Simon (Dark Angel)" writes

The manual is incorrect on this

If the voltage is 210-230 Vdc, then the solenoid is loading the circuit correctly, if it's >300Vdc, then the pcb is driving into an open circuit

Yes, 4.2kOhms is the correct resistance of the gas valves

IIRC the solenoids are captive on a plate - you could replace that, but it would be more dangerous than replacing the gas valve itself

In message , Heliotrope Smith writes

Do you not mean open circuit

Who needs a manual ?

Its fairly obvious what the problem is from his description - gas valve solenoid is O/C

OK, should I be putting my ohm meter on the terminals that connect to the red and black leads? If so, then its not a zero reading I'm getting, but rather a resitance greater than 10kohms

I assume that's a job for a gas fitter then?

I'll recheck everything in the morning, but the voltage between the red and black leads to the gas solenoid sent the needle on my multi-tester off the scale on the 250v DC setting (perhaps its time I invested in a digital meter).

I recently had a similar problem with a Potterton Netaheat Profile. I measured an open circuit on the pilot solenoid winding and the cure was a new gas solenoid module. (There wasn't time to mess around as it was very cold and the shops were about to close for the weekend.)

I should have asked whether solenoids were available separately as it turned out that the coil was easy to remove from the module by bending a twisted steel retainer.

Somewhat surprising was the finding that one solenoid was directly mains powered while the other was driven via a full-wave bridge rectifier on a small pcb inside the connection block. The rectifier means that depending on the operating voltage of a multimeter the resistance might appear to be higher than expected - perhaps even open circuit - when in reality everything is OK.

In my case the winding itself really was open circuit, but I could easily have misdiagnosed a perfectly good unit had I used a different meter.

John

In message , "Simon (Dark Angel)" writes

Yes, assuming that the link wire (white?) between the two solenoids is there

===> solenoid gone

So yes - pcb is driving into an open circuit then

The OP clearly is in need of a manual or he would not have spent out on a PCB that he did not require.

So you give him a refund on the board that he no longer requires then?

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In message , Heliotrope Smith writes

No - he asked for a pcb last week, I told him I was surprised that one of my pcbs (albeit over 3 years old IIRC) was faulty. I can't remember exactly what was said, but I'm fairly sure I did my best to establish whether it was the pcb or not. I rather think that time was short and he was willing to replace the pcb as this was the path of least resistance

If I'm wrong then I'm sure Simon will correct me, I have had over 100 pcbs go out this week and its difficult to recall every conversation

I give anyone a refund - once

Next time they want something, they can go and buy new and not waste my time

You see, I will do my best to diagnose and sort out the problem and get them back up and running - a service to someone who has had a part from me, and I am very good at it by now. I have no time for timewasters

I have no need for flow charts or such things, because I am probably unique in that I understand what is going on inside the pcb and its interfaces as well - I see the full picture

I know you dabble in boiler repairs, but if you depend on flow charts, it tells me that you don't actually understand what you are doing

Yeah - you could bend the bracket, but that is not really a very good solution you will not get it to clamp the solenoid in place properly

If you leave diagnosis of these things to me - the nht profile is completely different to the Suprima

A little bit of knowledge can be dangerous

Oh blimey, I seem to have started a bit of a flame war.

To clarify, Geoff is essentially correct, there is a bit more to the story though. I had reason to suspect it might have been the PCB as the system had been acting a bit peculiarly at the end of last winter, which I posted on here about, and was told thats what it sounded like (pump suddeny started running for no reason when the system was off). However, as the problem seemed to correct itself and didn;t come back, I left it.

When my system packed up the other week, Geoff did suggest it might have been the gas solenoid, however as this is not really a user servicable part and as it sounded like there was a problem with the PCB anyway, I figured this was most likely what the problem was.

I shan't be asking for a refund, because if my existing PCB does later pack up completely at some point later we're gonna have to go through this whole process again.

For anybody still following this thread.

British Gas have been and fitted a new gas valve this week for their = customary charge of =A3165, which I didn;t think was bad considering = these valves sell for something like =A380, plus whatever the new seals = for it cost.

When diagnosing the fault, it was quite amusing to see the gas engineer = working through a fault finding flow chart on his laptop, like the ones = mentioned elsewhere in this thread (seems even many so-called experts = still need a helping hand).

So anyway, after a very cold few days, the central heating is up and = running again.

Still not entirely convinced I need to take out their monthly boiler = care plan though, unless you suddenly need to be corgi registered just = to change a 3-port valve head or the programmer.

But anyway, thanks to all of those who tried to help!

--=20 Best Wishes Simon (aka Dark Angel) Dark Angel's Realm of Horror -