Potteton combi diagnosed dead for the sake of a spare part.

[Onetap]

SInce he doesn't know the original specs he has no idea of what "properly" would be.

Yes; that is why, with my limited knowledge of their workings, I'd be inclined to scrap it, as I had said.

A piece of resistance wire would "work" but be dangerous.

So why put the daft idea into his head? Besides which, I doubt that it would work.

 

[Gasguru]

I hope the wires to the sensor and the pcb solder joints have been checked.

 

[Deleted member 105431]

The boiler is ****ed-buy a new one!

 

[Agile]

It's not a standard aps it's an airflow sensor. Tony is usually on by now saying how it is a modified version of something they used on a cooker when he were a lad.

As I say, it's unique, obsolete and has no substitute.

I didn't need to as Namsag even remembers which cookers they were used on! My mother used to have one! Anyway I have been in Norfolk for the weekend, didn't see Dave though.

It is like the old glow coil igniters that used to be on gp40`s and majorca 2`s .

The resistance was under 2 ohms but they put a thermistor across it with a resistance of about 10k. It would not have any effect but just made them look "special".

It would be very easy to repair them with a new element.

However, most of those diagnosed as failed are as a result of faulty leads or connections.

Tony

 

[Cluesome]

post a picture and the part number I will hunt around in my old stock I may have one of these there, cant promise mind but also talk to the local stockist there should be some thing thats Simula enough there not exactly rocket science and will not damage anything if the fan is not running the boiler will not fuction so any air flow that will fit should do the job

Hi, thanks for taking an interest.

As it happens the chap fixing it checked the wires to the sensor and the pcb solder joints (which check out) and says the problem is with the sensor not re-setting itself. He said he would fit another sensor if I could source one but won't do anything ad hoc.

I could take a photo of the part if that would help. Or I have an exploded diagram I hunted down on the web. Can I send it to you? The Potterton Part No. is 300303.

Best,
Phil.

 

[Agile]

As it happens the chap fixing it checked the wires to the sensor and the pcb solder joints (which check out) and says the problem is with the sensor not re-setting itself.

Best,
Phil.

The sensor does not "reset itself" !

The PCB merely heats up the resistance wire in the element and measures the resistance which varies according to the temperature of the element and is related to the airflow across it.

But we should not be calling it resistance wire as thats specifically designed to maintain a constant resistance at different temperatures. Its probably pretty much a normal tungsten alloy as used in light bulbs. But it needs to be contact welded as it does not solder.

Tony

 

[Cluesome]

The sensor does not "reset itself" !

Sorry, I realise this phrase was something of a euphemism.

The engineer did a test where he isolated the unit from power, removed one of the airflow sensor connector leads, re-powered the unit and re-connected the (hot) lead. This made the flame ignitor go into a mode of repeatedly igniting on and off. He took this to mean that a. the lead works (he also tested it for current) and b. the sensor resistor does not give a true value from cold, so that sometimes it works and sometimes it doesn't.

The flame does ignite intermittently and temperamentally. For the most part of last winter I could get it to start by heating the kitchen with the oven to sauna levels and boiling water on the cooker (sounds daft, I know,) but even that doesn't work now.

Would that be consistent with perhaps a duff welded contact in the sensor that sometimes connects and sometimes doesn't but more likely does when the atmosphere is very humid? Sometimes it will work seemingly randomly. Sometimes if I switch it off completely and leave it for a week it will then work for one evening only. Again, maybe pointing to the welds within the sensor.

Ultimately I am no expert and am relying on advice. I think at this stage I may ask if the engineer minds replacing the connector leads to see what difference that makes, if any. Although I think he will consider it a waste of his time as he himself is sure it's the sensor.

Best,
Phil.

 

[Agile]

That makes me think that it might not really be the air flow sensor!

Another fault I have found a few times on your model is a "dropped" flame sensor which touches the burner.

Those have to be dealt with by a CORGI.

However disconnecting the flame sensor lead from the PCB should result in the flame lighting for about five seconds if thats the fault!

Of course the real situation is that your boiler is old and is due for replacement. You would need a real boiler enthusiast to be willing to repair it !

Tony

 

[ChrisR]

It would be very easy to repair them with a new element.

Which isn't available. And you just said you'd have to weld the wires.

Just because they look like something else doesn't mean they're anything like it.

Ask a boiler changing company. I haven't had any trouble getting hold of them though I haven't needed any for a while. Still got a couple but no idea where - so don't ask!

 

[Cluesome]

Hi,

I thought I'd let people know that there is a company advertising on eBay right now who have a small number of reconditioned Airflow Sensors, i.e. the part I was looking for, no. 300303, that is obsolete from the manufacturers.

In case anyone is still trying to fix their Potterton Lynx 1.

Best.