Gas and Oil Home Heating Furnaces - fan doesn't run constant
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09-25-01, 12:04 PM
I have a Coleman oil furnace that came with the double wide mobile home I purchased 10 years ago. The problem is when the furnace first starts firing and the fan kicks in to circulate the heat, the fan turns on only for a few seconds and then shuts off and then turns right back on again only for a few seconds. This process is repeated quite a number of times until finally after several minutes the fan runs constant without shutting off until the desired temp. is reached. Just recently I noticed and fixed a problem with water coming in from the roof and dripping on the furnace which left several spots with rust on and in the furnace. Could you be of any help??? Thanks for any help.
lynn comstock
09-26-01, 01:43 PM
When the home is cool in the morning, the cold air passing through the furnace drops the fan sensor temperature enough to turn it off. When the home is warmer, this cycling stops happpening.
Nothing is broken. If you reduce the night setback the problem will disappear. OR let it cycle. Most fan controls are not safely manually adjustable.
Nothing is broken. If you reduce the night setback the problem will disappear. OR let it cycle. Most fan controls are not safely manually adjustable.
Sharp Advice
09-26-01, 04:47 PM
Hello mfrancle
Welcome to this forum and the web site.
I have a sightly different take on your question. Based upon the problem discription you posted, the fan cycles on and off only after the burners fire up and not when the furnace is off.
Here's my take on your discription. The furnace {Burners On}is just beginning to warm up the firebox {Heat Exchanger} when the fan turns on. The fan switch, which senses the interior temperature, turns the fan on, then off again. The cycle then repeats several times and finally the fan remains on until the thermostat temp. is reached.
If this is correct, the fan "ON" temp may be set too low. Turning the fan ON too soon, cools the firebox faster then the burners can heat it up. The fan switch then reacts to a cooler temp and turns the fan off.
Some fan switches have adjustable temp on and off settings. If your does, the temp. dial will have a center slot for a screwdriver to fit into. Read the dial. Know which way to turn it prior to any adjustments made. Where ever it's currently set at, setting it up another 20 degress should correct the condition. If all else {Rain drops entering and rusting on the unit} with the furnace is okay.
Use CAUTION! Fan switches use full house voltage to operate. Do Not touch any of the wires by hand or with tools. Best idea is to turn off the power or unplug the heater during the adjustments etc.
Regards & Good Luck
Forum Moderator
Tom_Bartco
Energy Conservation Consultant & Natural Gas Appliance Diagnostics Technician.
Welcome to this forum and the web site.
I have a sightly different take on your question. Based upon the problem discription you posted, the fan cycles on and off only after the burners fire up and not when the furnace is off.
Here's my take on your discription. The furnace {Burners On}is just beginning to warm up the firebox {Heat Exchanger} when the fan turns on. The fan switch, which senses the interior temperature, turns the fan on, then off again. The cycle then repeats several times and finally the fan remains on until the thermostat temp. is reached.
If this is correct, the fan "ON" temp may be set too low. Turning the fan ON too soon, cools the firebox faster then the burners can heat it up. The fan switch then reacts to a cooler temp and turns the fan off.
Some fan switches have adjustable temp on and off settings. If your does, the temp. dial will have a center slot for a screwdriver to fit into. Read the dial. Know which way to turn it prior to any adjustments made. Where ever it's currently set at, setting it up another 20 degress should correct the condition. If all else {Rain drops entering and rusting on the unit} with the furnace is okay.
Use CAUTION! Fan switches use full house voltage to operate. Do Not touch any of the wires by hand or with tools. Best idea is to turn off the power or unplug the heater during the adjustments etc.
Regards & Good Luck
Forum Moderator
Tom_Bartco
Energy Conservation Consultant & Natural Gas Appliance Diagnostics Technician.