coleman evcon furnace model dgat070bdf not heating


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Old 11-23-13, 10:15 AM
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coleman evcon furnace model dgat070bdf not heating

I posted earlier about this furnace. I narrowed it down to a bad gas valve. it had 7" wc coming in but only 2" wc going out. I have replaced the gas valve and the valve now has 3.5" wc going out which is what it is rated for. the furnace seems to be functioning normal, it turns on, lights, the exchanger heats up, the blower comes on. the problem im having is that the house is not warming up. after the blower heats up, the exchanger cools off, and it just continues to cycle cold air. could this be a limit switch, or maybe a blockage somewhere? i am at a loss here.
 
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Old 11-23-13, 01:11 PM
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Could very well be a limit switch. That model is notorious for bad fan & limit switches.
 
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Old 11-23-13, 03:55 PM
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any idea how to test limit switches? I have multimeter with ohm option, just dont no what i should be looking for.
 
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Old 11-23-13, 04:10 PM
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Limit switches are a normally closed switch which open at a specific temperature. The next time the furnace acts up, kill the power, remove one wire from the limit, & check for continuity thru the switch. If you have continuity, the switch is closed. You can check the fan switch the same way except the fan switch is normally open & closes at a certain temperature. Both the fan & limit switches should have temperatures stamped on them (Usually on the mounting 'wings').
 
 

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