Please help - Can't Light Gas Pilot!


Old 12-06-08, 11:22 PM
Thread Starter
Join Date: Dec 2008
Location: Wisconsin
Posts: 3
Please help - Can't Light Gas Pilot!

Hello Forum from a nubie! This may be a duplicate post!
Has someone on this forum taken a gas furnace control apart and got it back together again successfully?
Bought a used propane wall furnace for my separate garage. Fuel is getting to the control, but the pilot bypass button is not letting gas thru to the pilot fixture.
The pilot bypass button presses in and fits thru the semicircle notch at the pilot position of the control switch.
It seems to me this has to be a failure of pilot bypass switch or a clog in the gas passage inside the control. The guy that sold it to me had taped the control gas inlet to keep bugs out.
Details of what I have follow:
The furnace is pretty old, but was used a few years ago. It has an Electric Unitrol control made by RobertShaw-Grayson. Electric Input is 110V, but the control is 24V. I think the transformer is inside the control as the control is warmer than the surroundings if the furnace is plugged in.
If you're still with me here, any responses are welcome!
Frank K.
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Old 12-07-08, 04:31 AM
Join Date: Jul 2005
Location: New York
Posts: 723
If I'm understanding your post, you are getting gas into the control but your are not getting gas out from the pilot tap. Did you confirm this is the case by removing the pilot tubing from the control and seeing if any gas comes out?

If this is the case, it is a bad control. There is no repairing these.

What kind of wall furnace is this? I'm not familiar with any that have 120 VAC going to an otherwise 24 volt control. In most cases there is a transformer in the heater somewhere
Old 12-07-08, 05:04 PM
Thread Starter
Join Date: Dec 2008
Location: Wisconsin
Posts: 3
Hi HankHill6018,
Thanks so much for your response! There is a plate on the bottom of the furnace that may have the furnace manufacturer's information on it. Right now it's covered with ice, but I have a propane torch to thaw that tomorrow.
Before I get to that, the Model Number of the control is 110ERBSO.1D LP.
I did not confirm the pilot tap gas blockage by removing the pilot tubing. so that gives me something to try. Thanks for that suggestion!
Regarding the 110:24 volt transformer, I haven't located any external transformer yet. This furnace has a circulating fan motor. Technically it's possible to use the iron in the motor as a transformer, but the motive for that approach seems unreal!
Is there any other electrical load common in a control when there's no pilot or burner lit that will raise the temperature of the control above ambient temperature?
I know the propane is getting to the control because I had to fix a gas leak at the control input elbow that resulted from the adapter hose I cobbled together to complete the connection to the propane cylinder.
Frank K
Old 12-09-08, 03:52 PM
Thread Starter
Join Date: Dec 2008
Location: Wisconsin
Posts: 3
Tho bad form, I'm replying to my own last post. Maybe this thread will be of interest to someone else!
One question I have for you Hankhill6018, is do I need the AC electricals to light the gas pilot light?
No gas is coming out of the pilot tap port of the control, but I have yet to check the electricals. Like you said, there is an external transformer hidden behind the fan motor. I don't know if it's working or not yet, but I'm thinking the pilot should light without 24V from the transformer.
For the rest of the story, the control has a date code on it of 08-73 which I take to be August of 1973. The manuf plate is oxidized, but the manufacturer is apparently Leo Siegle Inc, Centrailia, IL. It a patent number of 3,133,535 FWI.
So if I know for sure that nothing extermal except the propane source can prevent the pilot from lighting, I'm going to see what made this baby tick!
It seems to me the chances of finding a replacement control for this are pretty unlikely. One other feature to the control is a "speed" knob. After removal of the knob, there is a plastic ring gear with a single pinion running something inside. This must have something to do with control of the fan.
I would appreciate a response from you, Hank, to confirm that the pilot circuit should be independent of the transformer and speed control workings.
Frank K

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