Intermittent pilot ignition control - replacing cable/wires?

newdognewtricks

Hello,

Is it possible to buy intermittent ignition board cables without buying an entirely new control board? My Dunkirk boiler has developed a habit of not firing the main burner, but working again if I unplug and replug the combination PV, MV, MV/PV cable that connects to the gas valve. I feel like the whole IPI isn’t shot, there’s just a bad connection in that particular wire, and I could solve the issue if I just replaced the little 3 pronged combo cable.



For reference this is a UTECH 1003-600A.

Let me know what you think. Thanks!

EBEBRATT-Ed

If those are regular spade connectors, you could probably cut that plug off and crimp new connectors on. Or try cleaning and tweaking the existing.

I don't know if that wiring harness is a Dunkirk part or a Utec part. You could probably do a little searching and find out. Start with the boiler manual.

mattmia2

I would be a lot more suspicious of where the terminal solders to the board than the terminal on the wire.

newdognewtricks

mattmia2 said:

I would be a lot more suspicious of where the terminal solders to the board than the terminal on the wire.

Any idea why the main valve would lose power randomly from a bad connection then get it again after a replug?

@EBEBRATT-Ed I am hesitant to do much work myself as I’m a complete newbie and I’ve already spent $1,000+ throwing parts and labor at this thing throughout my HVAC company’s troubleshooting. If I messed something up I’d be pissed. What’s my risk here? What can I break if I try this myself? It seems like my tech would tell me I have to replace the whole board anyway…

Thanks guys, appreciate the help.

mattmia2

Are there any errors flashing(does this board even have any diagnostics?)?

Does the pilot valve light then the main valve not turn on or does the pilot valve fail too?

Find the instructions for this module for a more specific sequence but I think this control works by:

Start spark and open pilot valve
Prove pilot with flame rectification
If flame is proven, open main valve.

If it isn't proving flame which I think it is doing through flame rectification through the spark probe, it won't open the MV.

It needs a good ground path to the pilot burner to get a good current on the flame rectification sensing. You could be jarring something in to better contact when you unplug and plug back in the connector. Or it could be a bad connection in the board itself either for the MV or something else.

Jamie Hall

"Any idea why the main valve would lose power randomly from a bad connection then get it again after a replug?"

That is quite exactly what I would expect it to do if there were a bad connection pretty much anywhere in the signal path. It might be a damaged wire. It might be, as @mattmia2 sigguested a bad solder joint at the plug. The most likely point, however, are the plugs and sockets themselves, or spade connectors. Plugs and sockets -- particularly the Molex sort, which you may have - -are notorious for developing intermittent bad connection problems. Replacing the plug or socket -- or the entire harness -- may help, but only if you ensure that the mating socket or plug is absolutely clean and tight and free of corrosion. Spade connectors are easier to clean and free from corrosion -- but in both cases what you are looking for is the connection to not only be physically tight (wiggle is not an option!) but bright metal.

The same would apply to any other ground path connections.

Dave Carpentier

If you reterminate the wires, dont forget to label them (MV, MV/PV, PV).
If its the board side, Ive had to repair bad solder joints on many electronics (but not hvac). Its always where something is pushed on to a connection.. the joint starts to weaken and then goes open at the circuit board. The action of you unplugging and plugging in the connector wiggles it and solves it temporarily. That unit might be sealed and inaccessible to re-flow the joints though.

mattmia2

The terminals have a lot more mass than the other components and frequently don't get heated adequately when the board is wave soldered.

newdognewtricks

mattmia2 said:

Are there any errors flashing(does this board even have any diagnostics?)? Does the pilot valve light then the main valve not turn on or does the pilot valve fail too? Find the instructions for this module for a more specific sequence but I think this control works by: Start spark and open pilot valve Prove pilot with flame rectification If flame is proven, open main valve. If it isn't proving flame which I think it is doing through flame rectification through the spark probe, it won't open the MV. It needs a good ground path to the pilot burner to get a good current on the flame rectification sensing. You could be jarring something in to better contact when you unplug and plug back in the connector. Or it could be a bad connection in the board itself either for the MV or something else.

No diagnostics on the board unfortunately. The PV always works fine, the problem seems to be limited to the MV.

Now I’m wondering if the issue is the flame sensor - or lack thereof. As you can see in the original picture there is no connection to the SENS male spade. However there is a black female spade connected to the main valve, and a female spade just sort of floating in air next to the control board. I wonder if a tech took it out at some point and forgot to plug it back in?

Jamie Hall said:

Spade connectors are easier to clean and free from corrosion -- but in both cases what you are looking for is the connection to not only be physically tight (wiggle is not an option!) but bright metal. The same would apply to any other ground path connections.

There is definitely a lot of wiggle in the male/female spade connection.

mattmia2

Is that unconnected wire just connected to a screw on the body of the gas valve? If so it is probably for burner ground.

The pilot valve will open regardless, then it sparks, then if it proves flame it opens the main valve. It will probably close the pilot valve after some timeout if it doesn't sense flame but you would need the instructions for that control to figure that out.

newdognewtricks

Yes it is connected to a screw on the gas valve.

It’s a 5s time out but I don’t think I’ve ever seen/heard it time out. It always just seems like the pilot stays on and is available, but the main valve never opens.

EBEBRATT-Ed

If he (service tech) left a wire off call the service manager and **** him out. You should not be paying $$$$$$ for a system that won't work...................especially if they can't diagnose the problem

Dave Carpentier

On a wiggly female spade connector, you can sometimes give the "hoops" on the edges a bit of a squeeze to tighten it up. Squeeze a bit, test, repeat. If you go to far, use a small flat blade to pry it back open a bit.

newdognewtricks

Thanks for your comments everyone, I appreciate the help.

Do I have any options if the problem is the board's solder? Or would I have to just buy a whole new board? What about the terminals on the gas valve itself?

EBEBRATT-Ed

@newdognewtricks

if it's the board you would have to replace it. The terminals on the gas valve can be scraped and cleaned. I thought you said it was the connections at the board that are the problem?

newdognewtricks

Just did some troubleshooting and have some interesting updates.

1) The boiler does not start working again if you simply turn it off and on - you have to somehow break the circuit with the board.
2) I can actually get it to start working if I only unplug and replug the cable that connects to the gas valve - the other side of it (that connects to the board) can stay plugged in, along with the 24V cables.

Thoughts?

Thanks all.

mattmia2

try plugging that gas valve ground wire in to the burner ground terminal. Sounds more like you are making a poor ground connection to the pilot burner better when you disturb things.

Also look very carefully at all of the spark wire to see if it is chaffed or burned and shorting to the cabinet somewhere.

newdognewtricks

mattmia2 said:

try plugging that gas valve ground wire in to the burner ground terminal. Sounds more like you are making a poor ground connection to the pilot burner better when you disturb things. Also look very carefully at all of the spark wire to see if it is chaffed or burned and shorting to the cabinet somewhere.

Really? That spade doesn’t have an insulated cover. It doesn’t look like it’s been used.

Spark wire looks good as new.

Ground connection and terminals on valve:

mattmia2

It gives the current through the pilot flame a more direct path from the electrode back to the control to detect the pilot flame.

newdognewtricks

The plot thickens…turned off the boiler, unplugged everything from the board besides the spark. That’s MV/PV/MVPV, 24V, and 24V GRND. Yet the pilot is still lit. That has never happened. Normally once I pull the MV/PV/MVPV off the gas valve the pilot turns off.

Plugged everything back in and turned the boiler back on - now it doesn’t light the main flame.

What the heck is going on?

PS this is without connecting the burner ground. I was about to do that before this latest development.

mattmia2

24vac between mv/pv and pv from the control should be what opens the pilot valve. do you smell gas with it off?

You have the grouped connector unplugged completely and the pilot burner is still burning?

newdognewtricks

Nope, no gas smell. Just a boiler with apparently zero electricity and no cables besides the spark plugged in, but still with a lit pilot.

newdognewtricks

Maybe it’s more accurate to say the pilot never shut off after the main valve stopped firing. It was working earlier after the trusty unplug/re-plug.

newdognewtricks

Lol. Did the same old operation again and the pilot turned off.

Do all boilers taunt you like this or is mine just haunted? 

mattmia2

put a voltmeter on the main valve terminals. the valve might be bad. see if there is 24vac between the mv/pv and mv when the main burner won't fire.

EdTheHeaterMan

Have you tried placing this black wire on this terminal?
Before you do... check that the terminal is labeled (GRD). Either Burner (Grd). or 24V (Grd). GRD stands for Ground

hurt_happens

@newdognewtricks - were you able to resolve your issue?

I have the *exact* same issue, also with a Dunkirk boiler and this same ignition control module. 😄

The pilot works consistently, but the main valve is intermittent. When it works, the ignition control module tests at 24v, obviously the opposite is also true (doesn't work, circuit is open).

At first I thought maybe it was the flame sensor, but then I pressed on the plastic connector and *POOF*, it fired up.

It'd be nice to know how this worked out for you. I'm going to pull the cable off and clean up the connections the best that I can. I'll post back here if I resolve my issue by cleaning it up.

hurt_happens

There's zero corrosion.. the connections look shiny new. I tried bending them in a little to make a tighter connection, but that didn't resolve the short. At least I can wiggle the cable to kick the boiler on (BRRRR otherwise).

I'll see if I can pull the metal connectors out of the plastic outer connector (without breaking them) so I can get a better look at how well the metals parts are touching.

Jamie Hall

Is this a cable to cable connector? Or is the mating part of the connector perhaps soldered to a circuit board in the electronics? If the latter, there may be a cold solder joint between the connector half and the board.

mattmia2

is this the end at the control or the gas valve?

hurt_happens

I took the plastic connector off by carefully bending each of the 3 metal clips and sliding them out. Then I attached them directly to the ignition control module (sans plastic connector). They were a very solid connection / tight fit.

Sadly, the problem still happens. This seems to imply to me that there's a flex crack in the PCB of the ignition control module. My temporary solution is essentially to visit my boiler and just touch the plastic connector to cause the main valve to open. This is required about 50% of the time (anecdotally).

I already put the plastic connector back in before I snapped a photo of it.

Today I'll try removing the ignition control module and opening it up to see if I can find a visual indication of damage and/or somehow repair it, although I'm highly doubtful.

My assumption is that I'll need to replace the ignition control module, unless anyone here has a better idea of how to repair it. I'm comfortable soldering. It's surprising that this has happened to more than one person. Seems like a defect... perhaps the way the PCB is mounted in the housing allows it to flex when the housing is pressed against, so anyone why gives a bit of pressure to the outside of the housing will be in this same boat.

hurt_happens

@Jamie Hall and @mattmia2 - thank you both for responding. I hope my post didn't seem as though I ignored you. I believe it answers both of your questions, but if I'm misunderstanding please let me know.

mattmia2

ok, so it is the control end. the terminal probably didn't get enough heat when it was soldered. easy to fix if you know electronics. some will argue you should not touch a control. i'd test that the various lockout functions work properly if you for example disable the pilot before it tries to light or unplug the flame sense while it is firing.

because the terminal has so much more mass than the leads of the other components they don't get enough heat when they are wave soldered unless they are careful about controlling their process.

hurt_happens

The flame sensor and the pilot are a combined wire. I'm not sure I have a good enough understanding of HVAC to interpret your recommendation for testing the various lockouts.

I also have a hard time understanding how soldering points could be the cause, since it worked for so long and is now only working intermittently. To be clear, I'm not arguing or questioning your skills, just baffled.

Since the pilot works consistently, and it also requires the shared ground, it seems to me that *only* the topmost main valve terminal is the issue. Are you suggesting I could hit the terminal ends with a soldering iron and resolve this?

Nothing looks damaged in any ways, and my "flex crack" suspicion seems highly unlikely in this case since the board seems fairly simple and doesn't even appear to be multi-layered. Photos are below.

hurt_happens

There are TWO solder points for each terminal... so hard to understand how it could be that it's losing continuity.

hurt_happens

AND... even though I'm asking questions, I'm eager to take action - so I'll be heating my soldering iron momentarily. 😄

hurt_happens

newdognewtricks said:

There is definitely a lot of wiggle in the male/female spade connection.

I realize I hijacked this thread, but the OP never responded with a conclusion and I feel reasonably confident this is the same issue, especially now that it seems it might be related to insufficient soldering AND that a technician at the company told him to unplug/plug the connector as a solution.

I'm going to melt the soldering points for the main valve, then give all the terminals a light sanding before reinstalling. I'll post the results.

hurt_happens

Okay, that's done. It fired the first time, however since it was intermittent I can't know for sure yet if this issue is solved.

I'll update this thread once enough time has passed to confirm if this is truly resolved or not.

mattmia2

the works for a while then cracks happens all the time. if you flex the board and look at the solder you'll usually see a little crack in the solder that moves. could be other things with large leads like relays or power resistors too. relay solder joints tend to fatigue with vibration, power resistor and semiconductor solder joints tend to fatigue with temp changes

mattmia2

I think i see a crack around this lead for the relay:

Jamie Hall

Printed circuit board soldering is ... tricky. As noted, for production work wave soldering is used, and it doesn't always make a good joint. It could be a crack. It is just as likely -- if not more likely -- to be a cold solder joint which can look just fine but not be. And those tend to fail with time.

I hope resoldering does the trick for you.