Replacing flame sensor didn't fix ignition problem; Need ignition control module?

Motorapido

Background provided in this prior post https://forum.heatinghelp.com/discussion/186902/help-diagnose-intermittent-buzz-inside-boiler-cabinet-and-failure-to-fire#latest

So my pilot was lighting when the stat called for heat, but after pilot ignited, the burners didn't kick on. It made sense to suspect the pilot flame/spark assembly, so I replaced that assembly this morning. Drat. Problem persists. I rechecked all power and ground connections, cleaning up all the contacts. Still no go. I turned off the automatic damper when in the open position to take that particular control out of the equation. No go. Hmm. Some sort of divine inspiration told me, "Try tapping on some things." Using the handle of a screwdriver, I gently tapped no the ignition control module, and immediately the burners fired up. In summary so far:
1. Stat calls for heat
2. Pilot lights successfully
3. With pilot successfully burning, I hear a very faint on/off/on/off buzz, seemingly from the sparker, but it's hard to know for sure.
4. Burners fail to light, although pilot remains lit and the on/off/on/off soft buzz continued.
5. Tapped ignition control module and the burners fired up.

I already fired the parts shotgun when replacing the pilot/spark assembly. I don't want to randomly fire the parts shotgun again based on the results of tapping the ignition control module without some further insight.

I assumed that the ignition control module was a sealed circuit board with no mechanical devices inside to get stuck or hung up. But when I tapped it, the burners fired up. Is there some sort of mechanical relay in that ignition control module that wasn't opening/closing until I tapped it?

Time to fire the parts shotgun, buy the part and see what happens? Or does somebody have wisdom to share with me that I'm not figuring out on my own?

Hap_Hazzard

If it's responding to tapping, you might want to look inside and see if there are any loose connections or cold solder joints. If you can run it with the cover off, you might try turning off the lights an tapping to see if you can see any arcing,

Motorapido

Hap_Hazzard said:

If it's responding to tapping, you might want to look inside and see if there are any loose connections or cold solder joints. If you can run it with the cover off, you might try turning off the lights an tapping to see if you can see any arcing,

I'm assuming that there is the equivalent of an older-era automotive spark coil inside that module. Other than that, I'm assuming the remainder of the assembly is simply a circuit board. But based on insights shared in my prior thread, I'm thinking there is also a device inside this module that senses the flame rectification. Not sure which would be more likely to fail.

But regardless, if it's a cold solder joint or a bad spark coil or bad flame rectification sensor, it would be a matter of replacing that entire module anyway. So should I fire the parts shotgun and buy a new module? Ugh. At least I've saved a bundle on an emergency service call fee, labor fee to replace the flame sensor assembly, and I'll save on the callback to replace the ignition module (which, since we can't discuss price, costs about 7 times what Bernie Sanders wants to establish as the minimum hourly wage). I guess I'm still ahead of the game.

Chris_L

Rather than tapping on the control module, I would wiggle each connected wire, one at a time, to see what happens. (Sometimes the wire breaks inside the connector.)

Motorapido

Chris_L said:

Rather than tapping on the control module, I would wiggle each connected wire, one at a time, to see what happens. (Sometimes the wire breaks inside the connector.)

Good thinking. I'll give that a go.

ethicalpaul

And order a new module from supplyhouse.com so it's on the way in case those things don't work

JUGHNE

Was your new replacement pilot assembly an exact replacement?
Did not have a separate flame sensor?

Motorapido

JUGHNE said:

Was your new replacement pilot assembly an exact replacement?
Did not have a separate flame sensor?

I bought from Parts To Your Door, where I was referred by Peerless. That seems to be the Peerless parts sales subsidiary. I spoke to a person on the phone at Parts to Your Door before ordering just to double check the appropriate applicability of the part shown for my boiler on their website. My new pilot assembly is branded with a Peerless part number, specifically for my model of Peerless boiler, and it's the Peerless part that supersedes the pilot/spark assembly that came with the Peerless boiler. This new part, like the old one, is a bracket holding both the pilot and the spark components. The only difference is that the rod on the sparker/flame sensor is about 30% thinner than the one I removed. Also, the one I removed was attached with two screws into a bracket tack welded onto the burner tube. The new assembly attaches with just one screw. In the location where the other screw would have attached, there is a metal tit that indexes the part into the bracket so it doesn't wiggle. They probably made that change after service techs complained that it was very difficult to reach that upper screw (which it is).

Motorapido

ethicalpaul said:

And order a new module from supplyhouse.com so it's on the way in case those things don't work

Yeah, I suppose I should. I never heard of anybody having a failure with these before, though. I didn't think it was a consumable part. Probably good to have on hand just in case.

JUGHNE

Everything is capable of failure.

Also some parts are getting more difficult to obtain. Placed on backorder for 30-60 days perhaps.

ratio

Rats, it sure sounded like we had it figured out. The only part left to replace is the module, although failure to prove the flame still could be caused by a poor ground. Double-check all the ground wires/screws.

ethicalpaul

Mine failed a few years ago on my old boiler in a fashion that sounds very similar to yours. It was the dead of winter and I had to jumper out the valve and babysit it in order to get some BTUs into the house until the replacement arrived (DO NOT ATTEMPT).

When it came it fooled me at first because Honeywell decided to change the names or functions of one of the important hookups to it and buried that info deep in the fine print.

Don't feel bad if you have to go that route, you'll have all new ignition parts.

If you can't find one let me know, I still have my replacement on a shelf because my new boiler came with its own of course and I salvaged it.

neilc

Do you have a full 24 ~ 27v going to the module ?
no new thermostats ?

Motorapido

neilc said:

Do you have a full 24 ~ 27v going to the module ?
no new thermostats ?

Good diagnostic question. To test the voltage going to the module, I assume I have to test it with the stat calling for heat? The front of the module has a 24v input clearly labeled. It has two grounds, with one labeled Ground Burner and the other labeled 24v Ground. Am I testing between the 24v input and the 24v Ground on the module, with the female spade connectors still in place, or am I removing the 24v input female spade connector and the 24v Ground female spade connector and measuring voltage on those two leads? I have a good quality multi-meter that I have used extensively on various projects. I'm just seeking guidance on where to apply my test leads to test for 24 - 27 v going to the module.

Motorapido

ethicalpaul said:

Mine failed a few years ago on my old boiler in a fashion that sounds very similar to yours. It was the dead of winter and I had to jumper out the valve and babysit it in order to get some BTUs into the house until the replacement arrived (DO NOT ATTEMPT).

When it came it fooled me at first because Honeywell decided to change the names or functions of one of the important hookups to it and buried that info deep in the fine print.

Don't feel bad if you have to go that route, you'll have all new ignition parts.

If you can't find one let me know, I still have my replacement on a shelf because my new boiler came with its own of course and I salvaged it.

Thanks, ethicalpaul. Luckily, I was able to source the new module locally. Before I install it, however, I want to try to rule out any other conditions that could be causing this intermittent problem, so that if I find a problem other than the module, I can fix that problem and keep the new module on hand as an emergency spare.

neilc

Motorapido said:

neilc said:

Do you have a full 24 ~ 27v going to the module ?
no new thermostats ?

Good diagnostic question. To test the voltage going to the module, I assume I have to test it with the stat calling for heat? The front of the module has a 24v input clearly labeled. It has two grounds, with one labeled Ground Burner and the other labeled 24v Ground. Am I testing between the 24v input and the 24v Ground on the module, with the female spade connectors still in place, or am I removing the 24v input female spade connector and the 24v Ground female spade connector and measuring voltage on those two leads? I have a good quality multi-meter that I have used extensively on various projects. I'm just seeking guidance on where to apply my test leads to test for 24 - 27 v going to the module.

yes, stat calling for heat,
ground is ground, so either ground should work, even the chassis as ground,
pull the 24 black and stab the connector, and then the burner ground is already bare for you,

are the wires snug on the spades?
same question at other ends of the wires

Motorapido

My meter bounces between 26v and 28v when measuring the black 24v input wire, removed from the module connector and the stat calling for heat. So it seems that the transformer is provided appropriate power.

Oddly, so far on this very cold day in central Pennsylvania, the boiler has fired every time the stat calls for heat. So far today, it didn't get stuck in the pilot-only, pre-burner ignition phase. I think the module knows I'm angry and that a new module will arrive shortly, and I'll throw the old module in the trash -- so it's on its best behavior and performing without error. It's like kids before their birthday and before Christmas. Best behavior time.

neilc

and it's possible by moving and jiggling wires you cut some corrosion and are making better contact(s), or set a cold solder joint just right, or ??
it's still behaving ?

Motorapido

Yeah, a broken wire/crimp-spade joint I could happily deal with. To make sure the 24v input connectors and the ground connections are good, I removed all connectors, cleaned them with electrical contact cleaner, and hooked them back up. A cold solder joint would exceed my diagnostic skills. This type of work is frustrating since it's impossible to know if any jiggling you do while disconnecting and testing a wire could be reestablishing proper conductivity on another connection. So many variables. At this point, the only spade connectors I haven't removed and cleaned are the three that go from the ignition module to the gas valve. I figured I'd wait to see if what I've done has solved the problem. You never know when you disconnect a spade crimp connector if you'll end up damaging it, so I left those gas valve connectors along, to avoid introducing more variables.

HomerJSmith

I've seen this at least a half dozen times. Inside the module is a relay that opens up the gas valve. The repeated opening and closing of the relay points breaks the relay pin connection to the circuit board which results in an intermittent firing or a complete failure. When you tapped the module, you made contact between the relay pin and the circuit board and it worked.

If you open up the module and look at the circuit board, I think you will see a broken solder joint on a relay pin. You could resolder that joint and it would work. Technicians will replace the module. But you can do what you want.

There is a difference between knowing what fails and why it failed.

Motorapido

HomerJSmith said:

I've seen this at least a half dozen times. Inside the module is a relay that opens up the gas valve. The repeated opening and closing of the relay points breaks the relay pin connection to the circuit board which results in an intermittent firing or a complete failure. When you tapped the module, you made contact between the relay pin and the circuit board and it worked.

If you open up the module and look at the circuit board, I think you will see a broken solder joint on a relay pin. You could resolder that joint and it would work. Technicians will replace the module. But you can do what you want.

There is a difference between knowing what fails and why it failed.

Ah. Good info to know. Many thanks, HomerJSmith. Makes sense that the repeated impact vibrations of the relay closing could break a solder joint. I think I'll install the new module when it arrives and have a friend resolder the relay pin on the board of the old unit (this friend repairs and modifies guitar amplifiers and can make tiny, beautiful solder joints). If re-soldering that pin connection returns the module to health, that repaired module could be my emergency spare. I can make strong, ugly welds on a variety of metals. I can make ugly copper sweat joints. I can make ugly solder connections between two stranded wires, but I am way too lousy with my fine soldering skills to do this pin connection on the circuit board myself. A man needs to know his limitations, improve the things he can improve, and accept his soldering shortcomings and assign fine soldering work to those with better skills. That's my Sunday sermon. Amen. Hallelujah.

neilc

once you have that new module, and the old one repaired,
I think I would do the extra work and put the old "repaired" module back in to run and prove itself,
and keep the good new one "on the shelf"

Hap_Hazzard

Motorapido said:

Oddly, so far on this very cold day in central Pennsylvania, the boiler has fired every time the stat calls for heat. So far today, it didn't get stuck in the pilot-only, pre-burner ignition phase. I think the module knows I'm angry and that a new module will arrive shortly, and I'll throw the old module in the trash -- so it's on its best behavior and performing without error. It's like kids before their birthday and before Christmas. Best behavior time.

That's weird. Usually they only do that when a technician comes to your house. It's almost like it respects your troubleshooting skills.

Hap_Hazzard

neilc said:

once you have that new module, and the old one repaired,
I think I would do the extra work and put the old "repaired" module back in to run and prove itself,
and keep the good new one "on the shelf"

It almost sounds like you're laboring under the misconception that the new one can't be defective.

neilc

laboring with the conception that I would not keep a repaired unit to use in a next emergency , , ,
yeah, #smiling faces