I have an older Janitrol Moffat furnace in my garage. It was converted sometime in the past from propane to natural gas. It takes quite awhile for it to heat up enough for the fan to kick in and once it does, it runs only for 45 seconds then the fan quits. It will cycle like this all day if I let it with the burners going full blast but the fan kicking in and out. I have to shut it off after a few hours because it smells like it is overheating. We installed a new control valve and a new high limit switch with no difference noted. Do I need to build a shield to protect the switch from the direct cold air blast from the fan? Do i have to junk this furnace and replace it with a new one?
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1Here is a related question that might help you... diy.stackexchange.com/questions/130130/…– Jerry_ContraryJan 24, 2019 at 16:27
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The smell is likely to be just dust that has collected because of disuse.– Rohit GuptaFeb 2, 2023 at 13:22
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1 Answer
Hi because you said you replaced high limit control & gas valve, try setting the thermostat amperage with same amperage gas valve is reading. If these two points don’t read same amperage reading the stat can throw out its understanding of what’s needed and react as indicated.
You can try moving the high limit wheel points wider apart allowing fan to stay on longer.
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Follow up answer, when moving high limit control points wider be sure to hold wheel tight so it doesn’t move when setting points apart, if not held still the adjustment could damage or throw control out and not be refixable. Jan 3, 2023 at 2:34
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By the way I’m referring to the furnace fan limit grey box control on front body area of furnace. Jan 3, 2023 at 2:37
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3Your answer could be improved with additional supporting information. Please edit to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers in the help center.– Community BotJan 3, 2023 at 8:44
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