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Small Cabin Forum / Off-Grid Living / LP heater diagnosis
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paulz
Member
# Posted: 10 Dec 2023 01:09pm
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I have a Williams direct vent wall heater. Worked great for a few years but this spring it quit burning lp. The hardware store sold me a new thermocouple or thermopile, whatever you call it. Didn’t fix it.

Now, months later I’m taking another shot at it. Same thing, pilot stays lit but when you turn the knob to on it lets out a quick burst, then nothing. Anyone good with these?

Couple things… hope I have the new thermo wired right. On the left screw is the red wire (and a black one that goes to something else on the valve. The center screw has the white thermo wire. Right screw is empty, I think at one time I had a toggle switch there and the center screw. It says TH and TP on there, pretty sure I have it right..

Is there a testing way to bypass the thermo? Hard to believe the old a new ones are bad.

The LP line Ts off and also goes to the cooktop, works fine.

Again just a quick Whoosh, then out.
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darz5150
Member
# Posted: 10 Dec 2023 02:15pm
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Do you have a low oxygen shut off?
If you do you may need to blow it off with compressed air, or wipe it with alcohol if you can get to it.
I have to do this if dust gets on the cutoff sensor. When mine needs cleaning you can hear a click, then all gas is shut down including the pilot light. This has to happened when the heater was burning, and either was sweeping or using a vacuum cleaner by the heater.

ICC
Member
# Posted: 10 Dec 2023 03:02pm - Edited by: ICC
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What model Williams heater?

Have you the user manual? The manual usually has a troubleshooting section.

In my experience when a thermocouple is defective the pilot will not stay lit. If we are talking about the same thing, the thermocouple is a device that has one end that is mounted to be in the flame of the pilot light or flame. Some have electrical wire connections, some do not.

Heaters vary... some have a millivolt thermostat, either built in or remote.... What is yours?

All heaters will have a gas control valve and that could also be where the problem is.

Model number would be a huge help.

-izzy

paulz
Member
# Posted: 10 Dec 2023 04:58pm
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It’s a 3003622

https://c.searspartsdirect.com/doc/L0408134

No ox cutoff I know of. Pilot stays lit. Turn it to on, get a 2 second burn out of the burners, then back to pilot light, which never went out. Repeat, repeat, same thing.

I ran line straight to burners, bypassing control valve, works that way..

pabear89
Member
# Posted: 10 Dec 2023 05:00pm
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from the quick whoosh and out, I would remove the gas line from the control to burner and check for a plugging speck that is moving when the flow opens to the burner. I have had tiny spiders cause all kinds of problems from egg nests to their dead carcasses stopping the flow.

ICC
Member
# Posted: 10 Dec 2023 05:38pm - Edited by: ICC
Reply 


So if bypassing the control with a piece of tubing allows the burner to operate with a good proper blue flame and not self-extinguish the problem would seem to be either the valve itself or the wiring that controls the valve.

Page 21, troubleshooting, "E", indicates to try jumping the thermostat terminal on the valve. If that causes the valve to open and the main burner to burn okay, then the issue would be with the thermostat or thermostat wires.

There would also be a possibility that if the thermocouple end in the pilot flame is dirty or not positioned properly in the pilot flame, it may not be producing sufficient voltage to make the valve operate properly. Maybe just enough voltage to make it pop open for a second or 2 but not to keep it open. ???

It might also be a good idea to remove and inspect and clean the orifice. Also be sure the entire burner assembly is clean as pabear89 suggests. But if bypassing the control valve allows the burner to burn well the burner and orifice should be okay.

-izzy

paulz
Member
# Posted: 10 Dec 2023 05:40pm
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Yeah that occurred to me too..

But, it’s fixed! Turns out my model, with external thermostat, must have a connection between terminals one and three on the valve. I mentioned I thought I once had a toggle switch in there, don’t know where that went. I rarely used the heater, got an abundance of fire wood, but nice for backup.

Thanks guys, sorry to bother you.

Notes
Member
# Posted: 11 Dec 2023 09:16am
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From your wiring diagram on page 12 figure 12 you are missing a thermostat. The valve is powered at the center terminal and the terminal in your picture that has no wire on the screw.

paulz
Member
# Posted: 11 Dec 2023 09:54am
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Thanks Notes. My valve is the bottom one on that diagram. I have it wired just like that and it’s running at the moment, only instead of a thermostat I have a jumper wire clipped to the two terminals. Take the jumper off and it stops, pilot stays on.

gcrank1
Member
# Posted: 11 Dec 2023 10:39am - Edited by: gcrank1
Reply 


Would any old 3-wire 'stat for a typical home oil or gas furnace work on that hooked up to those 3 terminals?
How about one of those cheap RV furnace 'stats?

paulz
Member
# Posted: 11 Dec 2023 11:09am
Reply 


No idea. I just used a toggle switch before I’m pretty sure. Just turned it off before bed or whenever done heating the cabin.

I don’t know how many BTUs it is, it’s a pretty big unit, but this morning it took awhile to raise the cabin 5 degrees. I’m used to the wood stove now which does it faster, plus the wood is free, cleans up the yards and no tank hauling and filling.

I’ll bet one of those new tech units people swear by (Martin?), would do a better job of it, maybe I’ll look into one when I get tired of cutting wood.

gcrank1
Member
# Posted: 11 Dec 2023 12:08pm
Reply 


Could use the wood stove to do a good quick warmup along with the LP, when the wood dies out the LP will maintain for ya.
Fwiw, there are simple adjustable temp 'finger' switches that wired in as that jumper (or the prior toggle) would do the same, the finger contact or discon is made by the temp bending the finger.
You might have one 'in yer bins'.

pabear89
Member
# Posted: 11 Dec 2023 03:11pm
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I agree with grank1 here, using a simple spring contact thermostat installed on it for backup to your wood stove would keep me from having to get up in the middle of the night to add wood.

paulz
Member
# Posted: 11 Dec 2023 11:02pm
Reply 


Always been nervous about it running while asleep, probably because I installed it, lol, and the LP plumbing..

I've got the woodstove dialed in lately, a big piece of hardwood before bed goes all night, no getting up. I'm in a milder climate though, high 30s in morning lately. Inside cabin stays low 70s, 69 maybe by morning.


By February we'll see...

gcrank1
Member
# Posted: 11 Dec 2023 11:31pm
Reply 


Gee, Paul, we've been turning our home stat down to 62* for a good bit of time now as is to save on NG. At 69* I'd find it hard to sleep......

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