Help with Weil-McLain boiler - won't ignite


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Old 03-06-17, 07:22 AM
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Help with Weil-McLain boiler - won't ignite

Hi,

I'm new to this forum but am impressed by the wealth of knowledge I've already seen on here. I'm hoping someone can help shed some light on a boiler issue we're having.

We have a Weil-McLain boiler that I think is from the mid-90's (we bought this house about 19 months ago). Last year when it got cold, the boiler wouldn't work. I realized the pilot wasn't lit, and wouldn't stay lit, and ended up bending the thermocouple back a little bit and it was good to go and has been fine up until two days ago when it stopped working again.

This time however, the pilot stays lit but the burners won't ignite. The thermostat clicks, then there's a click at the boiler, but the damper doesn't open nor does anything else happen.

It seems obvious that the message is being sent and, to some extent at least, being received. So I assume it's some sort of control issue and not say, gas delivery?

Thanks for your time and help!

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Old 03-06-17, 11:24 AM
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redford,
The electrical circuit for heating systems, gas as well as oil is just a series circuit. To diagnose you just have to know the series.
The first thing you need or should have is a meter.

If you have a meter and know how to use it start with your tstat and check for 24V. If you have voltage the next step in your case would be the damper you mentioned. If you are sure your stat is working and your damper is not opening then check for 24V at the damper.

If your damper is the problem nothing downsteam, between that and the burner will not work. In your case I would concentrate on the damper. It most likely has a molex connector (plastic plugin connector) with 4 wires maybe. Check for voltage there.

What you can try is separate the connector and you should see 4 pins on one side and the matching holes on the female side. Two of those holes will start your burner when jumped if the damper is your problem.

This being only 24V there is no danger in taking a piece of wire that fits into those holes and inserting them into 2 holes until you find the right combination that starts the boiler. If successful you know it's the damper that must be fixed.

To double check yourself you can jump your 2 stat wires from the stat first to see if that works. If not then proceed to the damper. Since the damper isn't working my guess would be the stat or damper as a place to start.

Hope this helps a little.
 
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Old 03-06-17, 12:52 PM
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Any wiring Dia. On the cover of the boiler?
 
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Old 03-06-17, 01:47 PM
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Yes, I'm attaching a pic now.

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Old 03-06-17, 01:51 PM
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Thanks so much spott, this is very comprehensive and very helpful.

Does it matter if my damper can be set to hold-open? I tried that, which worked fine, but it made no difference to the boiler igniting. But maybe that's to be expected?

I do have a meter though I admit to having never used it. But I can do some quick googling and get a quick primer and give it a go.
 
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Old 03-06-17, 03:04 PM
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If you have a meter and you can locate the transformer and the limit switches we may be able to walk you through some TS,what model is the damper?
 
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Old 03-06-17, 03:05 PM
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BY setting it to open unless it is activating the switch to send power to the burner it will make no difference. It sounds like your best choice is to get a piece of tstat wire if you have it and just try jumping the stat and then the damper. It's only 24v and it is safe to do. These are the same as regular switches and for testing purposes can be bypassed.
 
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Old 03-07-17, 06:07 AM
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spott - does it have to be thermostat wire, or can it be another kind? I don't think I have any wire and will need to go out and get some, so I guess it might as well be tstat wire, but wanted to ask first. Uploading some pics of the damper info in a sec.
 
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Old 03-07-17, 06:13 AM
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Here's the damper and info.

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Old 03-07-17, 08:02 AM
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No, it doesn't have to be stat wire but because of the small terminals and it's on 24v it is what fits best. It can be any wire or jumpers that work.
 
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Old 03-11-17, 04:26 AM
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spott you are the man!

I've been slammed the last couple of days and it's colder today and we're facing a few days of real cold, so I finally focused on this again.

I didn't have any wire so in a pinch I used a paper clip (hope that is ok). When I jumped one set of the pins in the molex it sparked and made a click but that was it. The other set I tried started the boiler! I was thrilled. So it's the damper, you're right.

I'm going to get some thermostat wire today so I can jump it and let it run more safely. I assume I can just be the manual thermostat for a bit? Open the damper, put my jumper in, let it run until the temp is ok, and then shut it off? Do you see any issues with this plan?

Thank you so much again!
 
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Old 03-11-17, 07:28 AM
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As long as the damper stays open when bypassed you can run the system normally with the stat. With the damper jumped, try shutting down the stat and the boiler should shut down normally.

As long as you make sure the damper stays open, and it should, you will not have to shut the boiler down manually. It should work off the stat. The stat operates the damper and with the stat satisfied it will cut power to the damper and everything else downstream to the boiler so if you don't mind the damper being open you can leave it that way until a more convenient time.

It will not cause any damage. Just like the stat it is only a switch.

Good to hear you are back on line. If your temps are dropping like ours you are going to need it.
 
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Old 03-11-17, 10:40 AM
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Wonderful. I can't thank you enough.

Yes, the damper should be staying open fine. When I change the switch on it to the open position it runs, the little bar from the motor going into the vent turns and it all seems fine (and sounds like it did before it stopped working properly). I'm planning on using my IR thermometer to check it once it runs for a bit so that it seems like exhaust is escaping as it should be.

Great point about the thermostat still working as-normal while it's jumped, I didn't think of that. I'll probably sit next to it for a bit for the first time or two, just to make sure it's running (and exhausting) fine, but I'm optimistic this will do the trick.

We're looking at some big house remodel projects, including the likelihood that we'll tear out the old boiler heating system in favor (sadly) of a furnace (because we have to replace the a/c too -- sheesh). So I was going to be really bummed if I had to spend a bunch to get us through the last part of the winter only to probably tear the whole system out in the end.

So again, thank you for your detailed help, I really do appreciate it.
 
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Old 03-11-17, 04:53 PM
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Well I just tried using my jumper wire and it worked to get the boiler going. I realized though that when I jumped it, the boiler would run regardless of what the thermostat said. The t-stat was on, but it was set to a heat temp that was below the current temp, so there was no reason the boiler should've fired.

With that in-mind, and realizing that I may need to find another set to jump in case the ones I picked were the always-run ones, I let the boiler go for a bit just to see if I could warm the house up. During this time I kept checking the vent pipe temps above and below the damper, and they didn't seem drastically off.

After a few minutes, I kept waiting to hear the pump kick-on and start pumping the water out, but it didn't come. Then a minute or so later it stated to make this terrifying shaking/clanking noise, that sounded like it was reverberating up the (outflow) pipes and up into the house. I'm not gonna lie, I was really scared at one point, so I yanked out the jumper wire to shut it down and I ran.

Everything subsided after a min or so and it seemed like any potential disaster was averted, thank the Lord. Then I snapped this pic of the gauge (below).

I've never looked at it much in the past, but I'm pretty sure I've never seen the water temp this high. I realize the boiler runs for a long time when it's circulating the heated water, so my only assumption at this point is that the molex connector, of which I was only jumping a portion, also has some control over when the pump runs? My best guess was that the water overheated because it wasn't being circulated. Maybe that's wildly inaccurate?

The other weird thing that happened was afterward, hoping for a mini-miracle, I plugged the molex back in, and as soon as I did the damper started to turn. The weird thing is, it was already set on hold-open, so why the heck did it turn/run as soon as I plugged in the molex?

At this point, though I'd love to fix this myself, I'm starting to think it may be a job too big for me. Though I'm still a little shaken from the clanking just a few minutes ago, if I thought I could reasonably sort it out without killing myself I would definitely try some more.

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Old 03-12-17, 09:13 AM
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redford,
Your high limit on the aquastat should have shut the boiler down. There may be more to this than just the damper.

I would start with the aquastat and take some voltage readings. Can you post a pic of your aquastat with the cover off to see wiring.

Back at the damper, between the motor and the pipe you will see a shaft probably flat. With the stat turned up it should be vertical which means the vent is open. If it's flat take a pair of pliers and gently see if you can move it to the open position. That should make the end switch to start the burner.

Sometimes they just stick. If you can turn it and the burner starts shut the stat down and see if it closes. Then restart the boiler with the stat to check. If nothing happens again you may have to go to the aquastat and take some readings with your meter.

The pics will tell me more. If you're not sure about meters and their use this may be out of your skill set.

It may be the vent but the fact that it didn't shut down on it's own is telling me it may be in the aquastat. I have bypassed the vent before with no problems. The aquastat being between the boiler and damper should have killed the power to the boiler on high limit since the aquastat sends power to the damper it shouldn't have made a difference it was jumped. There's more to this unless I'm missing something so until we know I wouldn't jump anything else out for safety sake.
 
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Old 03-12-17, 11:11 AM
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Yes, the bar from the damper is indeed flat. I set the damper to hold-open (the only way currently to get it to move on its own), and it made some noise and tried to turn but didn't make much progress (definitely not all the way to vertical), so I used my fingers to gently turn it and it kind of sprang to vertical after I hardly used any force. Went back upstairs and turned up the t-stat, it clicked, something on the boiler clicked (as before), but nothing happened and the boiler didn't start.

Tried putting the damper in the auto-whatever mode, and activating the t-state continues to do nothing. It's like it's not getting the message because it doesn't really even try. So I think you're right, it's not just the damper (thought that does seem to have a problem as well).

What does the aquastat look like? I'll google some to see if I can find a pic, but at the moment I'm not sure what that part is.
 
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Old 03-12-17, 04:02 PM
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It's the control on the boiler, most likely grey and says Honeywell. It's where you set the high limit and your stat wire goes to. The cover should slide right off if you loosen a screw on the side or top and expose all your wiring to the pump and stat.

When you find it see if you can post a pic with wiring exposed. and model number. Should be on the inside of the cover.

I'm watching The Natural with Redford. Started at 6:30 on Starz.
 
 

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