My combi 80 recently took the 2A fuse out on the main pcb. I got a new pcb but yes you guessed it it took the fuse out on that too. Any ideas as to what is the most probable cause? Does anybody have a circuit and or wiring digram they could email me?
I have had nothing but trouble with this boiler and it is only 18 months old, this is the 3rd time it has gone wrong!!!!! Can anybody recommend a good combi boiler as the next move for this one is the skip.



This message was edited by paulf on 12-10-03 @ 7:09 PM

Circuit or wiring diagram of what? If the boiler and it is only 18 months old you should have the M.I. for the boiler which has a wiring diagram in it.

If you are refering to the PCB then these are not available.

Why your comments regarding scrapping the boiler?? I would suggest a decent boiler repairer be found. Trace the cause of the fault not blame lack of fault finding ability on the boiler.

All boilers run the risk of going wrong. You can't blame your lack of diagnostic skills on the boiler.

Alan

Is 3 faults in 18 months common then???? hence the reason for wanting to replace it. I basically want a boiler that is reliable. If my products where this unreliable I think a few customers might be chewing my ass off! I am fed up with being without hot water and heating esp. this time of year!!

You say your products out of interest what are they?

Back to your boiler no three faults in 18 months is not reasonable but then you also give no history of the installation. Who carried it out, was the system correctly flushed, is it correctly installed and what were the previous faults.

Have you disconnected any external controls from the boiler that could cause the fuse to blow?

Alan

What we have here is a competent DIYer who (without reason) goes out and splashes good money on a PCB instead of calling people who can effect repairs. I can just imagine if a heating engineer were to replace a PCB with no cure, what the paulf would have to say.

Either Paulf can replace ALL 240 volt components one by one until the fault is fixed, or call an engineer who can fix the defect.

Maybe some useful information for anybody else finding the fuse blowing on their combi 80.
Yes I took a risk on the PCB but being as a recon pcb was only £20 it wasn't much of a risk (if anybody wants to know where to get these drop a message here).
If I had initially realised there was a wiring layout and fault finding diagram inside the front cover I would need not have asked the question initially.
Anyway onto the fault finding.
1) Using a multimeter check for any shorts on the mains transformer,mains gas valve solenoids,circulator pump and fan. One of these components is likely to have a short on it although according to the company that supplied my pcb it is not unknown for components on the mod. pcb to take out fuses due to a short also.
2) It seems the pump is the first component to be switched on via the righthand most relay. Therefore if the fuse blows as this relay kicks in (as I noticed it did in my case)then you can be fairly sure the fault is on the pump. It seems the next component to switch on is the fan, followed by (logic would assume) one or more of the gas valve solenoids.
Obviously I wouldn't recommend anybody starts messing around with the main gas valve but if as in my case you find it is the pump then you have just found your problem.
AlanE it isn't my lack of diagnostic skills, I am a qualified electronic engineer (I took a chance due to lack of info at the time, a gamble maybe)
After contacting 3 local engineers and been quoted at best 2 weeks to come and fix the fault I didn't have a lot of choice. Potterton of course offered to send somebody for a fixed fee of something like £250 regardless of whether the component had been a 99p fuse or a £130 PCB (I would have been unhappy if it had of been a 99p fuse as I think would have most people. On top of this they only give 30 days warranty!!!!
DP "I can just imagine if a heating engineer were to replace a PCB with no cure, what the paulf would have to say."
I would say what a crap boiler engineer same as I did about the guy who came 5 times and replaced numerous pcb's to fix my fairly new TV. When I decided to take a look myself it seems he failed to notice a large copper pad without any solder that should have been connected to a capacitor!! Now I'm no TV engineer but I do have 2 good eyes.

Paul email me on rannochservices@999ntlworld.com. You will have to remove 999 from the address for it to get to me. Will give you test points and advise on what to look for

Paul I wasn't critising your diagnostic skills I was just trying to point out you can't condem the boiler just because you was unable to locate the fault.

In the same way you haven't critisised the design of your TV because an engineer failed to find the fault.

Alan

Just an interesting little update to this thread (which I would have done earlier had xmas and my boiler not got in the way)!!
As you could see I determined that indeed the pump was the problem and set about finding a replacement sometime before xmas. The pump a Myson compact CP61 did not seem to be very easy to come by. I seached the net for a few suppliers, the highest quote I had was from a well respected supplier that has been quoted on here a few times (from the threads I have read) and was £150 ex. vat and delivery!!!!!!. After some shopping around i got a brand new pump for £59 and paid the extra £6.50 (as opposed to £3.50) for next day delivery. I don't know what the rules for this forum are so please drop a msg. here for the supplier I used. I must say that there are some suppliers that are are quite frankly robbing people which is sad.
Thanks for all the previous offers of help and a Happy New Year.

Because you are not a professional you would not know that those pumps have changed name. They are widely available and many plumbers merchants sell them, usually for less than £60.

If you have to keep blowing fuses as part of your fault finding then you should use a low value fuse say 250 ma.

A better procedure is to disconnect the fan, pump etc at their conectors and measure their resistance and apply ohms law. After all you did say that you were an electronics engineer! You cal also apply power externally to these mains driven components. Repeatedly powering faulty components through the PCB is likely to cause it to fail.

When I hear that soneone has used "repaired" parts then I think "cheapskate"! I went to someone who had fitted one of these recon fans and the boiler was not working because an internal part of the fan was blocked.

Tony Glazier

Agile Services

Because you are not a professional you would not know that those pumps have changed name. They are widely available and many plumbers merchants sell them, usually for less than £60.

If you have to keep blowing fuses as part of your fault finding then you should use a low value fuse say 250 ma.

A better procedure is to disconnect the fan, pump etc at their conectors and measure their resistance and apply ohms law. After all you did say that you were an electronics engineer! You cal also apply power externally to these mains driven components. Repeatedly powering faulty components through the PCB is likely to cause it to fail.

When I hear that soneone has used "repaired" parts then I think "cheapskate"! I went to someone who had fitted one of these recon fans and the boiler was not working because an internal part of the fan was blocked.

Tony Glazier

Agile Services

Well thank you "Mr Agile" for pointing out the obvious "you are not a professional (I presume you mean plumber)". If I were I would not be asking questions here now would I? (by the way you have no need to answer, this was more of a rhetorical question, if you don't know what this means I suggest you look it up in a dictionary).
My purpose for posting here was to help people in a similar situation, not to hinder or demean unlike yours presumably?
It is completely obvious that you are an imbecile and have not fully read my post (or at least understood it). As if you had you would not have made the blatant mistakes in your response that you have (i.e. I fitted a repaired PCB NOT a fan as you have seem to have indicated in your reply!).
If you had also read the post correctly you would have noted that I found the wiring diagram after I had initially attempted to diagnose the fault. For your information powering components above their rated current specification (good electronic design prevailing) where a fuse is in place rarely causes them to fail, that is the purpose of the fuse (i.e. to protect the circuit from drawing excess current and damaging more expensive components in the first place). If this wasn't the purpose of a fuse then we need not fit them. We may as well just use a transistor/diode etc as our fuse, after all the component value is somewhat similar.
I would suggest that people like you who are of little or no help on these boards unplug yourself from the Internet and take up something like crochet as a hobby instead. Maybe you would be of more use giving your "professional" advice on a topic such as this at the local W.I.
By the way I also suggest you use a spellchecker when making a post, or learn to type, you might also try not making double posts as this uses precious energy and disk space of people kind enough to provide these message boards.
People like you who have "superior knowledge" make a mockery of these self-help message boards. Also considering the tone and content of your reply I would suggest that in future it may not be a good idea or advertisement for your company.
If I were looking for a “professional plumber” it would be a cold day in hell before I contacted Agile Services.
On a closing note I would just like to let you know that my boiler is functioning perfectly at a fraction of the price that a "professional plumber" (like yourself no doubt) would have charged, thanks to the friendly advice I have received here and from others.
Do have a nice day.