Halstead Best keeps burning out PCB help please

[geoff@cetltd]

Nor would I

And, since the fan is driven by a relay, I doubt that a s/c fan would kill the aquastat pcb

 

[Paul Barker]

Are you sure you have a good contact when testing the thermister, it might be faulty or you aren't making good enough contact with it, but it isn't the main fault in any case.

In time honoured fashion there is more than one thing wrong.

 

[strontium239]

Just in case you are still interested, the thermistor was OK, called Halstead TS again it is 1 Mohm on the Best. this time they suggested the ignition board for the same symptoms. I suddenly realised, the only reason I thought the board was US was because Halstead said so and it had the funny voltage cycle. It seemed OK on a bench test so I have just put it all back together and it fired up straight away. My current theory is that the overheat cut out light is US and that disconnecting the power supply is resetting it. I will wait to see if it goes again and do a reset before touching anything else. If not then it is a dodgy connection or dry joint somewhere. I think the hot looking resistor on the original board is meant to run hot, it has a hole in the PCB and it connects direct to the switched live hence probably passes quite a bit of current and would look a bit brown after 6 years. Thanks for the suggestions.

 

[geoff@cetltd]

YEs, I've seen them with the outer coating completely gone

still holding the correct resistance

 

[ChrisR]

NB if it won't reset, you have to turn the thermostat right up and have a call for heat, or it won't reset. And it takes a second or two. I think it tells you in the manual in one place but not everywhere it mentions the reset button.

 

[tinymole]

Hi All, I'm new to this forum and found this topic by google search. The symptoms are identical to my own.

I replaced the Aquastat on my Halstead Best 60 two days ago and it worked until now, but has failed again. I can quote strontium239's original post to describe exactly what is happening -
"No lights, no fan, pump runs and Aquastat clicks (sounds like a relay) every 18 secs. Pin 1 on ignition unit starts at 4volts rises to 30 then the click then it goes back to 4 and rises again."

The thermistor is just over 1MOhm at room temperature, so seems to be ok. Just wondering if you ever got to the bottom of the problem, or if your boiler has been running ok ever since?

Thanks in advance.

 

[tinymole]

Glad to report I have solved the problem

It turns out it wasn't the aquastat after all, but the ignition and gas valve pcb. Strontium239 was probably on the right track in guessing it was a dodgy connection or dry joint on a pcb. In my case I can confirm it was.

Trying to diagnose the problem, I cut the pink wire between the aquastat and pin 1 of the ignition unit, which was displaying the fluctuating voltage. It seemed that the voltage problem was coming from the ignition pcb rather than the aquastat, so I opened the ignition unit (a bit tricky to get the plastic case open, but do-able).

There was a very obvious dry joint caused by heating on one of the pins of the central relay on the pcb. In fact it was so bad that the copper track on the pcb was broken. There were also a couple of less obvious ones on an adjacent resistor. I have a picture of this which I'll try to upload with this post.

Re-soldering the suspect joints did the trick and the boiler is working fine again. I could have saved myself the price of the new aquastat

Hope this might be of some use to anyone else experiencing this problem.

Regards,
Tiny Mole

View media item 51974 View media item 51975

 

[bodgemandcockup]

I had the same problem and fixed it in half an hour.......after spending two days on and off trying to decide which part was causing the problem.

I found 3, possibly 4 dry joints and a load that should not have passed inspection. How do they get away with it?

Its a shame my initial search did not turn up this particular thread although several others from this forum.

V pleased not to have been ripped off £150 possibly £250 for new parts

I assume Halstead boilers are no more?

Boiler ~12 years old and otherwise pristine

oops forgot to say thanks tinymole and the rest of you

 

[yenmit]

Thanks tinymole et al.

I had exactly the same problem;
"No lights, no fan, pump runs and Aquastat clicks (sounds like a relay) every 18 secs. Pin 1 on ignition unit starts at 4volts rises to 30 then the click then it goes back to 4 and rises again."

Inspected the ignition and gas valve pcb to discover it looked just like the one in tinymole's post. A few minutes with the soldering iron, including soldering in a couple of lengths of wire to bypass some suspect copper track and the boiler is up and running again.

3 people with the same problem in the space of a couple of months; looks like age is catching up with the pcb.


Thanks all, saved me much time, effort and money,

Yenmit

 

[tinymole]

Really glad I could give something back to the other forum users. Makes the effort worthwhile, as Ive got good help from such sources myself over the years.

I have a theory that 95% of faults with any type of complex technology are down to bad/broken/dry electrical connections. In most cases of bad solder connections, they are caused by circuits not designed to dissipate the heat properly from the higher wattage components, thus melting the solder, which results in even more heat being generated, and thermal runaway. Pcb mounted relays seem to be a particularly common culprit.

Last week I fixed a dell laptop that stopped working, again the charger socket pins had de-soldered as they carry quite a high current. A few months ago the heater relay on my bosch dishwasher was exactly the same as on the halstead boiler. I suspect in most cases its not worth the repairman's time or effort, as the customer will pay for whatever new parts he wants to supply. Bet it wouldn't happen in the third world where people consider it worth the effort to repair rather than throw away.
[End of Rant]

Anyway, im very happy to have helped. Hope more can benefit from our collective experience.

Good luck.

Mark

 

[ianbgas]

Thanks especially to tinymole but also other contributors for helping me repair a Halstead Best 60db boiler which had been behaving intermittently, on the first visit springing into life without me being able to resolve what the cause was, on the second failing to exhibit a problem, on the third appearing not to work due to a slight water leak, then working when dried out.

Today, the boiler refused to work, making diagnosis easier! On heating demand, the pump started and there was a periodic click from the boiler (perhaps every umpteen seconds, just as on the first visit) but no fan. Based on previous help from tech support at Dimplex (who themselves I believe have stopped doing gas boilers), I knew the overheat stat was ok (short, not open circuit), that the thermistor was ok (resistance above 1 megohm), that the fan was ok (resistance around 40 ohm) but wasn't being powered. Everything pointed to the gas valve/ignition module, which I couldn't get into on-site.

I placed an order for a new one, then viewed this forum which gave me the confidence to get into the module (not easy, the main thing being to free the black spade connection section using a scalpel). It was immediately apparent that the track around one of the relays had been eroded away to the point where one pin was definitely isolated and another suspect. I guess that the copper track reached the point where connection was intermittent, then finally gave up, due to the current being carried, acting like a fuse. Whether there was a manufacturing defect at the start, I can't say. There was no sign that moisture had caused the fault, so I believe the water drips were a separate issue. That relay powers the fan, which explains why the fan didn't run, and I guess the clicking of the relay (the low voltage section which operates it was fine) was due to lack of response from the fan pressure switch.

Repair was possible using solder, but for good measure, I added enamelled copper wire links. When the unit was put back in the boiler, it sprang into life, avoiding the need for an expensive new module.

Thanks all. Ian B gas (538432) www.ianbgas.co.uk

View media item 56746 View media item 56747 View media item 56748[/url]