Potteron 80 Gas Combi Blown

25 Jun 2007
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United Kingdom
My boiler was fitted with an old external timer and I had a new internal one installed on the circular bat on the front. The old timer was left in place and I decided to remove. I removed the timer and used a connector to bypass where the timer would have been in the circuit and attached the wires accordingly (I left the switch wire out). I had tested this and it worked fine. However, the second time I tested the boiler switch wire made contact with a metal appliance which caused a short. Now none of the boiler status lights illumate and the machine doesn't work.
I've replaced the 2A mini fuse and installed a new 3A fuse on the plug, but fear something has blown on the PCB. I'm guessing that an electronic part close the point of entry has gone. Any ideas?

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Hermanator said:
However, the second time I tested the boiler switch wire made contact with a metal appliance which caused a short. Now none of the boiler status lights illumate and the machine doesn't work.

That description is suitably vague and presumably describes a feature of your work which was defective?

Its difficult to suggest what MIGHT have failed in your case.

A professional would trace the incoming mains supply and see where the discontinuity occurs.

I assume that you have checked the consumer unit? ( fusebox! )

Hi, thanks for your quick reply Tony.

I was simply testing the unit and I didn't wire the switch cable at the time because I didn't want the boiler to come on. I didn't think the switch wire would be live so left it exposed for a second while I switched the machine on. I thought that the switch wire was made live from the timer end of the circuit, but it appears the boiler had made it light and hence discharged when it touched the appliance it was being tested on.

I think I might get myself a multimeter and do some quick diagnostics check, I could check the current over the internal 2A fuse at a minimum and try some tracing.

I've checked the consumer unit but it's worth checking that there is actualy power going to the unit! Thanks for that suggestion I will try it

You need to check for VOLTAGE, not current!

Even a simple neon screwdriver MIGHT be enough for a competent person to find the fault.

Using a multimeter to check the current in the mains is likely to blow up the meter if not the user!

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The right hand connection to the overheat stat seems to be hanging loose !!!

That interupts power to the boiler if its the overheat stat. It might be the frost stat though. Anyway put the wire back on and see what happens.

You also need to increase the system pressure to about 1.5 Bar.

Nice clear pictures!

You are Agile indeed! I forget to mention that I took out the connection on the right to make it easier to see! I also drained the system because I figured if I have to change the thermostat I would need to have it drained.

Glad you like the pictures. :)

When I used the Voltimeter over both terminals I got a reading of 240V. Am I right in thinking that if the part was working properly there would be no difference in potential over the terminals and so would have a reading of 0V? Would also explain why changed the mini fuse did not make any different - i.e. there's no current reaching that far into the circuit.

you could have damaged pcb,discon electric to appliance undo 4 small pozi screws pull it out look at back of pcb,are all solder runs correct is there any burning marks on solder posts.
Check the solder top left of the board on the back.
The frost stat (disconnected) is open when it's warm and happy, closes on temp fall.
Hi, the top left of the back of the board is scorched!!!

What should I do? New PCB time?

Thanks for everyone's help so far! I'm really grateful :)
pcb problems on these boilers are very common the smallest short circuit can end the life of pcb sooner than later.
pcb has to be correct for any more tests to be carried out hopefully transformer is not damaged.
good luck.

I bought a replacement PCB and this seems to have solved the problem! A cost of £90 + VAT and I even got it at trade price too :)

I used http://www.interpartspares.co.uk/stockists/index.php to find the stockist and the part that I need.

http://www.keeptheheaton.com/cgi-bi...HOP= &PN=potterton_PCB_s.html#a102425#a102425 also had the PCB at a cheap price but since i wanted it today i bought from a local supplier

Big thanks to Agile, ChrisR, just_thinking - all of who have saved the day!

I can now have a shower! :p


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