Worcester Junior

[AllyBongo]

Problem with this one is when a demand is on, the boiler was firing up for a short time then cutting out and the red light was flashing 4 times per sec. Checked both sensor, and they read within the range stated in MI's. MI's say next to check the resistance across the fan black and white leads, I tested across the fan terminals. MI's say it should be 75ohms to175ohms. I only got 64ohms. Going by MI's it says replace the fan. The fan seems to be running ok tho and the APS is made and ignition starts. APS works ok, although it takes a few seconds for the switch to close after it has been on. The boiler locks out with the cover on and off. When I left tonight it had ran for about 20 mins without lockout, so they're going to phone if it happens again. Would the fan reading low ohms be the problem?? Anything I haven't checked.

Cheers for any help guys, got a little experience in break downs but still learning

 

[AllyBongo]

any ideas guys

 

[arran197]

Which Junior is it, the Greenstar?

 

[AllyBongo]

No, standard efficiency

 

[SimonJohns]

Have you checked continuity of no and common when fan off?

May find you have a faulty aps

 

[arran197]

24i Junior RSF (discontinued Aug 2007) literature - Worcester, Bosch Group UK installer site
Would suggest the fan speed it too low, so fan is probably a good place to start.

 

[SimonJohns]

Fan isn't spinning. So that is a valid point. But this fan is either in or off

So need to be checking why it either isn't comin on or if the aps is affecting the startup of the fan

I haven't got the process diagram of the programming so can't say

Will need to check both. But first eliminate the op's suspitions. So as they can learn. Then build on that to fix the boiler if it isn't the aps

 

[AllyBongo]

Fan is coming on and APS is made, APS is a two wire switch not three. Switch seems to take a few seconds to shut off

 

[GrahamM]

The Fans can be temperamental on Worcesters. It may be kicking in at low speed but not hitting high so going to lock out.
Sometimes there is no clear 100% indication what may be the exact cause of fault so you have a bit of trial and error. The fault flow fault flow diagrams for these get to a stage where it says replace the fan and if that does not fix problem replace board. Sometimes you have to take an educated guess.
You have checked the usual suspects, sensors and APS. You do not appear to get the MI's spec for readings on the windings so I would be inclined to look at fan.

 

[arran197]

APS's always take a second or 2 after the fan slows down to click out. Not very familiar with these boilers if I am honest, so I can't really comment much further. I assume them fan on these is AC constant speed, rather than DC variable?

 

[SimonJohns]

Yes ac constant off or on

 

[AllyBongo]

Thanks for the replies, I'll speak to the customer to see if problem is back. Will prob look at replacing the fan, as MI's say.
I'll let you's know the outcome

 

[RoryD]

Problem with this one is when a demand is on, the boiler was firing up for a short time then cutting out and the red light was flashing 4 times per sec. Checked both sensor, and they read within the range stated in MI's. MI's say next to check the resistance across the fan black and white leads, I tested across the fan terminals. MI's say it should be 75ohms to175ohms. I only got 64ohms. Going by MI's it says replace the fan. The fan seems to be running ok tho and the APS is made and ignition starts. APS works ok, although it takes a few seconds for the switch to close after it has been on. The boiler locks out with the cover on and off. When I left tonight it had ran for about 20 mins without lockout, so they're going to phone if it happens again. Would the fan reading low ohms be the problem?? Anything I haven't checked.

Cheers for any help guys, got a little experience in break downs but still learning

4 times per second 2 options:

[TD="width: 344"][/TD]
[TD="width: 350"]CH or DHW Sensor fault or out of position.[/TD]
[TD="width: 167"]E[/TD]

[TD="width: 350"]Air pressure switch fault or condense in tubes.[/TD]

[TD="width: 350"]Fan fail or stiff.[/TD]

[TD="width: 350"]Blocked flue.[/TD]

[TD="width: 350"]Faulty harness.[/TD]

[TD="width: 350"]Board fault.[/TD]

[TD="width: 344"]Flash 4 times per second[/TD]
[TD="width: 350"]Gas Valve mode switch on min or max.[/TD]
[TD="width: 167"]F[/TD]

[TD="width: 344"][/TD]

 

[arran197]

To save starting a new thread, I'm having this problem on a tenant's boiler. I put it down to replace the PCB, which was done by someone else. Been back today and the fault is apparent again. It's flashing 4 times per second, sometimes fires and works fine, sometimes goes to lock out after about 30 seconds of the fan and pump running. Sometimes does it after the heating or dhw has been running a while. Sometimes it goes to fire then locks out as it's sparking.

I've spoken to Worcester who suggest the new board is faulty, I've spoken to my technical supervisor who suggests the same. But I'm not so sure. I've had a faulty new board on a Glow Worm before, but I rarely find a Worcester with a board fault and I doubt the new board will also be faulty. I tested the DHW thermistor and that was reading ok, linked out the low water pressure switch, which had continuity through it anyway, as did the overheat stat. Continuity through the APS when the fan runs.

The only thing I can think is that the harness is broken somewhere, causing it to lock out.

Anyone else got any ideas?

 

[RoryD]

it seems my last post has been corrupted, I'll check my laptop out Arran and see what it says

 

[AllyBongo]

With the one I had problems with it was the APS. Worked sometimes then just stopped, if it fires when you take the cover off it will be APS. Also listen for the switch clicking before it locks out

 

[arran197]

I was thinking that, but every time I checked it, there was continuity through the APS. The fault finding basically says it's the pcb, aps, sensors, everything almost! Helpful! Not!

 

[AllyBongo]

I thought the APS was ok to but you cant really test it properly cause it only failed with the case on! Had the same prob the other week with a Vokera compact, when i took out the APS there was a seal on it that had dried and peeled off which was causing the fault, again this one only failed with the cover on

 

[arran197]

I don't really know what to think tbh. The APS looks quite new and the fault happens with the case on or off. Every time I check it it's working, so I removed it from my fault diagnosis.

 

[smhstu]

These boilers suffer from the aps melting where the tubes attach to it. Make sure you take it fully of and check the state of the connections to the sensing tubes, i've had them melted and the aps dropping off.

Just a thought

 

[arran197]

Hmmm, will check it. Spent 2 hours there again today. Don't want to be spending any more time there. I did have to refit the board though, it wasn't in very well! Lol! I've ordered another PCB & a wiring harness, as this one has rusty connectors. Not sure if that'll cure it, but worth a shot. Will also check the other thermistor, but it's so temperamentle that you think you've cured it and then it goes again. Had it running for 20 minutes fine, then gone again & took 15 minutes before it came back on without locking out. But it isn't heat related because the boiler was stone cold when I got there.

 

[AllyBongo]

Id change the aps before doing anything else, at least it will rule it out! And they're not expensive

 

[southcoastboile]

yeah had the same the other day, did a thread on it, if aps is melted then it will need a new pcb also as the fan cuts out before the burner. Probably a stupid idea but is everyone overlooking the obvious and its not just the venturi that needs cleaning? they dont always make boilers lockout on startup as im sure you are aware

 

[newgas]

common fault on these is a fan relay on the pcb sticks causing the burner to stay alight after the fan goes out and damaging the aps, dangerous imo.

 

[arran197]

Just to finish up from the posts I made, I went back to this boiler on Friday with a new wiring harness, APS and a PCB. Boiler was going straight to lock out again after running the fan. So was making me think the APS was actually the fault. Tried it several times, but kept doing the same. So I changed the APS and the wiring harness. Bit of a pain to get the wires round the back of the hood to the overheat and the WPS, but after it was all done, the boiler fired up every time, about 20 times! So fingers crossed that has finally dealt with the little sodding thing.

 

[Nas]

I wish I had seen southcoasts thread last week ...... could had saved myself a few hours
Had the Exact same fault on a 28i junior last week . It turned out to be both the APS and the PCB. Must be a common fault on these standard effiency models

 

[SafeGasInstall]

Just to finish up from the posts I made, I went back to this boiler on Friday with a new wiring harness, APS and a PCB. Boiler was going straight to lock out again after running the fan. So was making me think the APS was actually the fault. Tried it several times, but kept doing the same. So I changed the APS and the wiring harness. Bit of a pain to get the wires round the back of the hood to the overheat and the WPS, but after it was all done, the boiler fired up every time, about 20 times! So fingers crossed that has finally dealt with the little sodding thing.

me just to ask you did not fit the new pcb ,did you ?

 

[arran197]

No, it had already had a new PCB. Which didn't solve the problem. So after further talking to Worcester (who said it was a board fault in the first instance as well as me and my technical supervisor saying the same) they diagnosed a faulty PCB. But to be honest, the aps was causing some confusion when checking the continuity of it. Having said that, the harness was in crappy condition, so I think it was a combination of the 3.

 

[Billy Bob Bob]

pcb,s are very weak on this boiler got one doing this at the moment had a universal aps fitted for testing reasons,faults the same fitting a new pcb tomorrow

 

[arran197]

Strange really, because Worcester boards are usually good. I just hope it's still working as I type and it hasn't died again!

 

[Nas]

pcb,s are very weak on this boiler got one doing this at the moment had a universal aps fitted for testing reasons,faults the same fitting a new pcb tomorrow

Learnt this the hard way. I Replaced the APS with the old PCB still in , It immediatly took out the APS again.
Had to get another APS and replace it at the same same time as the PCB to fix it. Ran out quickly hoping it would last...

 

[newgas]

Being an SE I would/could have been seriously out of pocket with the parts changing thats going on, I wish I had access to parts like you chaps.
In my world you have to diagnose and rectify the problem first time for a satified customer who will the pay you if not.....

 

[arran197]

When you work for yourself I bet you make sure you know what the problem is by spending more time at the job. My management say you should spend 30 mins tops diagnosing. They want a minimum of 7 breakdowns attending per day! Kind of puts a lot of pressure on you if you come across a boiler you're not overly familiar with.

 

[newgas]

When you work for yourself I bet you make sure you know what the problem is by spending more time at the job. My management say you should spend 30 mins tops diagnosing. They want a minimum of 7 breakdowns attending per day! Kind of puts a lot of pressure on you if you come across a boiler you're not overly familiar with.

Like the more experianced fixers will say repairing boilers is an art and being good at it can take years and lots of out of pocket moments to get there.