Potterton Lynx problem

[jb007uk]

Hi,

I have an ageing 15 year old Potterton Electronic that is once again giving me problems.

I have no problem with hot water, however the central heating is giving me grief.

After firing up the boiler, the lights on the neons on C.H. Temp indicator quickly go up to max and the neons on the sequencer drops down from full flame to within 30 secs. The boiler then sits there for ages before firing up again and going through the same routine.

Strangely enough the Rads upstairs where the boiler is located are hot despite the amount of the time the boiler has been fired up, however the rads downstairs are cold.

Any help grately appreciated.

Rgds - Joe
[email protected]

 

[Agile]

It rather sounds as if the diverter valve is stuck IF it fires again say 15 minutes later.

These boilers are getting a little long in the tooth now and unless its in very good condition it is questionable whether its good economy to repair it unless its something simple.

When they were new they worked quite well but unfortunately the design has several water connections which can leak and wet the control PCB.

A favourite failure point when the PCB get wet is arcing under the connector block on the motherboard where the power enters. Luckily we have several spare PCBs in stock as they are getting difficult to find now. I expect BG will say they are unobtainable!

Tony Glazier

 

[gstens baxi]

Sounds like scale in heat exchanger or pipe work to me.

 

[jb007uk]

Many thanks for taking the time and trouble to reply.

If there any way that I can check the diverter valve to see if it is operating O.K. ? I can buy a new one from Ezepart for £50.00 but it is pointless if that is not the problem. I have checked the heat exchanger which seems O.K. Would this be the problem if the hot water was working O.K. ?

Thanks - Joe

 

[Agile]

An experienced engineer would confirm the diverter valve failure by feeling the temperatures of the connections to the diverter valve in CH mode.

It is impossible to diagnose a boiler fault with 100% accuracy over the internet when its a non professional describing the problem at the boiler.

Since you evidently want to save money, I would suggest you get the part if you think you can fit it.

Only dont blame me if its not the cause!!!

Tony

 

[jb007uk]

Hi Tony,

Many thanks for the prompt feedback.

Whilst not being a Gas Fitter I am a qualified electrician and spent a number of years working as a service engineer for both Creda and Hobert and therefore not exactly a novice. Therefore could you please tell me what I should look out for on the connections of the diverter valve ?

Finally, I shall not hold anyone responsible for offering advice on the subject at hand, as we are all aware establishing the fault is the hardest part, the repair is generally always straight forward.

Rgds - Joe

 

[Agile]

Nothing really, new fibre washers, silicone grease on the washers and on the threads. All easy for anyone doing it professionally.

Electrics are much easier because electricity does not leak out onto the floor and cause damage!!!

You can also measure the current flowing in a cable whereas measuring water flow inside a copper pipe is much more difficult/expensive!

Tony

 

[meldrew's_mate]

Is this the mark one or Lynx II?

Probably showing my ignorance but are we talking of the Lynx with the Honeywell type diverter valve ? If so suppose the sync motor has failed, in this case (there is no positional feedback) the valve would stay in DHW position and cause the rapid increase in boiler temperature as described. You can test for this by turning off the power to the boiler and trying to operate the small manual lever, on release it should return smartly to the relaxed (DHW) position.

With the power on you can feel the lever being driven to the CH position, if it doesn't go a simple change of sync. motor may be the answer.

For anyone who is in need (and CORGI reg'd) I have managed to squirrel away a couple of new MK 1 Lynx motherboards, these are the ones with a couple of plug-in boards, not the single board Mk2 type. It's about time they got put to use.

 

[jb007uk]

Thanks lads, for all your feedback. Things have got worse with the boiler since my original post a few days ago the rads upstairs are now not getting warm/hot at all and the boiler is now noisy, although sounds like the fan, and is rarely firing up.

Rgds - Joe
P.S. just to answer a previous question the Potterton Electronic was installed in 1989 and perhaps is on its last legs. I shall try a diverter valve as a last resort.