Don't you just love intermittent faults?

[Dannypipe]

Got called yesterday, then customer called back and said don't worry the boilers working again.

(Transpired he had taken it apart and cleaned the flame rec probe the numpty).

Then I get called today, the boilers done it again.

I get there and the boilers working totally fine.

It’s a Main Combi 24 HE.

It's running fine for me, but customer says it goes to "Burner Failure" sometimes when running water.

I checked amongst other things,
the gas inlet and burner pressures (max/min)
The condensate trap and pipe work.
The micro amps on the flame rec probe (5 micro amps)
The thermistor was about 9K
Both inlet filters on the cold main
The fan's coil (310 ohms).
The diverter and pump proving microswitch.

I didn't check the venturi, and I have a suspicion that there may be a blockage in the plate HEX as there was a rattly sound as hot water was drawn off.

Really weird one though. It worked fine for me, I ran the hot tap for about 10 mins solid and no issue..

Anyone got anything to add to this list. I'm going to pop back tomorrow and take another look.

Hard to repair a working boiler!

Having a bit of a frustrating time with combi's this last few days. This is the second one that's left me scratching the head. Not good.

 

[Dannypipe]

aps are prone on these boilers same as baxi 105

Funny you should mention that.

Firstly I have an issue with a Baxi 105 that's about five mins away (but I don't think it's the APS on that one).

Secondly I also had my concerns about the APS.

It's tucked away right at the back, top left of the boiler, and tracing the cables was a pain in the backside, and I was pushed for time.

I do heavily suspect a dodgy APS, as I was already suspicious, and you if you say they're prone to faliure of the APS then thats enough for me. I'm gonna have to test it.

Thanks.

I will of course conclude this once I know what it is, for others to use in the future.

 

[Dannypipe]

I had this or similar, flame rectification lead. Just needed bending over the top of the flame on the burner. And if he's had it out himself that could be it.

I put the multimeter inline on the flame rec probe. It was pulling 5 micro amps. The display actually read -5.

I didn't think too much of the - symbol. Should I have!!?

 

[Leo21]

I put the multimeter inline on the flame rec probe. It was pulling 5 micro amps. The display actually read -5.

I didn't think too much of the - symbol. Should I have!!?

Its not the continuity of the lead, it's the position. They can be miss aligned with the flame, so won't detect the flame. Bit like a bad pilot and a thermocouple. Aps are week, and can be knocked out on hw due to increased bp.

 

[Billy Bob Bob]

aps is failing change it fault cured

 

[Dannypipe]

I love you fellas, (in a straight, man love sort of way of course).

I will change the APS tomorrow. I will change the flame rec probe too simply because its a cheap part and the customer has been messing with it.

 

[Billy Bob Bob]

I love you fellas, (in a straight, man love sort of way of course).

I will change the APS tomorrow. I will change the flame rec probe too simply because its a cheap part and the customer has been messing with it.

to date with this fault,with exactly the same symptoms i have replaced around 80 aps,not one rec probe but if they been fiddling i would share your views danny

 

[Dannypipe]

Wow!

Well thanks very much for this insight. I wish I did more on the breakdown side. Some months I'll have loads, other times, it's all installs. My work is nothing if not varied!!

I will change the probe just simply as it's a cheap component, and like I say, I have no idea what he's been doing to it. The blokes a vet, so has no place inside a combustion chamber. He may have bent it, and I don't want to risk having another call out in a month or so if it also fails after I've done the APS.

Thanks very much to everyone. I will change it tomorrow evening (gonna be a late one for me as I have a mental day booked as is!)

 

[Leo21]

As I posted earlier I've had his fault with the probe, the most embarrassing bit is it was me who left it miss aligned after servicing it. Popped it back in line and hey presto. As you say though it's rare and only happened to me once.

 

[Billy Bob Bob]

Wow!

Well thanks very much for this insight. I wish I did more on the breakdown side. Some months I'll have loads, other times, it's all installs. My work is nothing if not varied!!

I will change the probe just simply as it's a cheap component, and like I say, I have no idea what he's been doing to it. The blokes a vet, so has no place inside a combustion chamber. He may have bent it, and I don't want to risk having another call out in a month or so if it also fails after I've done the APS.

Thanks very much to everyone. I will change it tomorrow evening (gonna be a late one for me as I have a mental day booked as is!)

when you fit the modified aps aim the tubing connections towards the fan so make sure the brackets in the right place

 

[Dannypipe]

Cheers all.

I'll let you know how I fare!

 

[wazzer]

ON INTERMITTENT PROBLEMS LIKE THIS i CHANGE THE THERMISTERS THEY CAN READ CORRECTLY ONE DAY/TEMP BUT NOT ON ANOTHER.....You look up and caps lock is on !!!

 

[diamondgas]

Thanks very much. I will look at this.

So if the lead goes closed circuit, the PCB will then the trap is full/blocked. Is this what you test for?

Yeh that's the idea to stop the condensate backing up to far! I've noticed condensation on the insides of the traps and wondered if it in anyway effected the trip? Can recollect replacing a couple of traps and the fault not returning even though the condensate pipe wasn't blocked/frozen! Since then it's one of the tests I'll carry out.

 

[Dannypipe]

Well I've ordered an APS. The original model has been discontinued and replaced with another Honeywell one. (I've had this same thing with a Baxi combi a few years back. This it's the same APS).

Anyway, I'll pick it up tomorrow and go stick it in.

I really need to get another thermistor test lead I miss it.

Done a couple more repairs today. Seem to be having a glut of break downs this week.

 

[Billy Bob Bob]

Well I've ordered an APS. The original model has been discontinued and replaced with another Honeywell one. (I've had this same thing with a Baxi combi a few years back. This it's the same APS).

Anyway, I'll pick it up tomorrow and go stick it in.

I really need to get another thermistor test lead I miss it.



Done a couple more repairs today. Seem to be having a glut of break downs this week.

replacement should be the white round type,not honeywell

 

[Dannypipe]

Ah right, I was looking at the merchants screen, must have been looking at the discontinued one. Thanks Mark.