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Furance comes on then goes off after

3K views 15 replies 6 participants last post by  hvac dude 
#1 ·
Furance comes on then goes off after a few second started after I change the white rodgers 50M56U-843 control kit I have rheem furance about 10 years old..The air condition works fine.:(
 
#3 ·
If the fault diagnostic light on the 50M56U-843 is not showing you the problem then either it's faulty or you need to test your thermostat circuit. Turn off furnace power. Remove the stat wires in furnace from R & W and put a jumper between R & W and turn the power back on.
Let us know what happens.
 
#5 ·
Does the small fan turn on? the igniter glow??? how about flame at the burners?

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#7 ·
check ground, clean flame sensor.....can you take a picture of igniter

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#8 ·
Comes on goes out

it is an universal nitride igintorit part number 21dD64-2 it was install at the time the 50M56U-843 was installed it came with the kit.now before the Air condition went out ,the furance was ok i had a bad control panel it was (burnt out) i changed the panel and now the furance will not work I will clean the flame senor and let you know,
 
#10 ·
Even if the igniter glows it doesn't mean it will be hot enough to light the gas....I would check the voltage across the connector first....check the resistance also.... replace the igniter......
 
#14 ·
if you have a multimeter with DC miliamp, connect the meter in serie with the flame sensor. the measure should be 2.0 - 4.5milliamp
 
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