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Re: intertherm furnace model MGHA070AAFC-01 cuts on and...
I assume this is a gas furnace? If so its most likely your fan switch. This is set to come on after the "Chill" is gone on the furnace and go off a few moments after the flame cuts off. there are several different kinds but you will find it if you trace the wiring from the fan motor (usually the colored wire red, blue, or yellow and NOT the black or white or brown) goes to it. If the colors are hard to see use a good lite and some alcohol to clean them up some.
Hope this helps and please rate me accordingly Good Luck.
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Most of these furnaceshave their flters in the front cover or door and needs a mohair type cut -to-fit sold by lowes dept. stores. If it doesn,t get air. it will trip-out the hi-limit switch at the top box located next to the fan.
The only thing that tells the unit to come on and off is the thermostat so I would definatly say it is it. When you turn the system back on, does the a/c run normally? If it does, then it's the problem with the heating side of the tstat. Also, does the fan come on when you put it to on and then turn of when you switch it back to auto? If it does, then the system is working fine, its the t-stat. Let me know if you have any more problems.
Make sure fan relay is wired correctly (G) wire. Ensure the fan on therm is not on, it should be on Auto or off.
If your furnace is short cycling because it has to keep heating your home, the delay in the control board may be staying on to compensate for the exchangers getting hot. If it heats normally, then put your attention to your thermostat.
Set the heating system on aux heat only. Fan should not be on, if it does stay on after a heating cycle, see if the furnace is heating normally, and reaching temp as desired before the heat comes off. Then check the therm wiring, pull the face of the therm, disconnect green wire (fan) and try the heating again.
Downstream of your fan discharge there is a little plastic assy. most likely that will have a pickup tube and a piece of vinyl or latex tubing attached. First check to make sure that the pick up tube and/or tubing does not have a restriction. If it is clean use an ohm meter to read resistance across the switch to verify it is operating.
is the thermostat set on fan on? Be sure the thermostat fan switch is all the way in the auto position..If you have a circuit board with a g terminal that is a gas furnace. Turn power off remove and isolate the green wire then turn power on. Let me know if it still runs. If it does not the circuit board is the most reasonable problem