This is a '93 Goodman gas model furnace. From what I have read, I believe it may have a bad limit switch. Where would this be located and how can it be tested? There is a small Black component (roughly 3x2")with a Blue on/off switch located on the furnace where gas passes. I believe this may be the limit switch. ANy ideas, if this is it or if any other component can cause the above symptoms?:confused:

Both fans? Indoor blower and draft inducer blower? Main limits don't typically cause both those fans to fun. It is brobably a roll-out limit. See PC board for a diagnostic light blinking. Roll-outs have a small botton on the top of them, if you gently push it it will click if they tripped. Labman has made several posts this month describing what these look like.

Yes both fans were running. I could unplug start cap on small fan, turn switch in unit closet , and small fan wouldn't come on, but could hear other internal fan still come on. I removed and reseated hose from one sensor, removed to check clean other components. (Thermoswtiched, flame detect). After this I turned switch back on in closet, and fans still came back on. I went to thermostat to select heat while fan was running, raised setting to above current temperature, waited, ignitor never came on or burners. Then, I only switched thermostat fan from auto to on, and the furnace ignited. After igniting I switched thermostat from 'on' position back to auto. When the temparture matched the setting, burner did shut off, and fans turned off slightly afterwards like normal. Seems to be working, now, but may have an intemittant problem and something is going out. I suspected/suspect a Limit switch. I will try to find labmans descrp.

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Originally Posted by Garzato

Yes both fans were running. I could unplug start cap on small fan, turn switch in unit closet , and small fan wouldnt come on, but could hear other internal fan still come on. I removed and reseated hose from one sensor, removed to check clean other components. (Thermoswtiched, flame detect). after this I turned switch back on in closet, and fans still came back on. I went to thermostat to select heat while fan was running, raised setting to above current temperature, waited, ignitor never came on or burners. Then, I only switched thermostat fan from auto to on, and the furnace ignited. After igniting I switched thermostat from 'on' position back to auto. When the temparture matched the setting, burner did shut off, and fans turned off slightly afterwards like normal. Seems to be working, now, but may have an intemittant problem and something is going out. I suspected/suspect a Limit switch. I will try to find labmans descrp.

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Did you look for tripped roll-out or spill switch limits?