No heat in Auto

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  #1  
Old 11-03-05, 06:28 PM
Don Rao
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Angry Forced hot air furnace problem -no heat in auto

My T-stat checked fine. I get heat only when the fan is in "ON" and not when in "AUTO". I replaced the Relay and the problem persists. At desired temp, the burner kicks in but the blower comes on only when fan switch is in "ON"! I noticed the limit switch cutting off the the power to the burner when the fan is not blowing and the duct gets too hot. Can somebody help me on this?
 
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Old 11-03-05, 06:42 PM
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What brand of unit is it?

How old is it?

Standing pilot, or electronic ignition?
 
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Old 11-03-05, 06:42 PM
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Fan problem

Either the "heating" speed of your fan motor is gone or whatever control sends power to the fan in the heating mode is malfunctioning. When you put the thermostat in the fan "on" position, it engages the fan in the "cooling" speed regardless if you have A/C or not.
 
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Old 11-03-05, 07:43 PM
Don Rao
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Talking Forced hot air furnace problem -no heat in auto

My unit is 15 yrs old and it says "Snyder General from Chicago" on the cover plate. I am not sure if the company still exists. I did not realize that only cooling fan comes into play when the fan is in "ON" position. Is the heating fan a low speed or high speed one? If the multispeed fan is gone, is that somethign I (as non technical professional) can replace it myself? If so, I woudl like to try. How much woudl it cost roughly to replace a fan like that? I assume the limit swtich is OK? I just joined this forum today and I am really finding it very productive! Thanks to both of you for your quick responses.
 
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Old 11-03-05, 07:51 PM
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Snyder General

Snyder General is now ArcoAire (I think) & a division of ICP which in turn is a division of Carrier.
Easiest way to check if the motor is the problem is to unplug the heating speed wire (usually low [red]) & once the furnace goes off on limit, see if you have 120 volts from the heating speed terminal to ground. If you do, the motor is the problem. If not, there is a control problem.
Replacing the motor is usually not a big deal. Getting the motor off the fan can be the hard part. Check it out & post back in the same thread.
 
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Old 11-03-05, 08:01 PM
Don Rao
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Will do and check back tomorrow. Thanks!
 
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