Intertherm furnace/ac unit model MGHA-090ABPQ-01

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Coolbluestreak
Posts: 3
Joined: Sat Oct 06, 2012 5:53 pm

Sat Oct 06, 2012 6:07 pm

Have a furnace/ac unit has a switch on the front and one side of the switch is for cooling and the other side is heat. Cooling side works a/c unit comes on and blows cold air, flip it to heat (and yes I adjusted the thermostat) and all it does it hummmmm. It kicked on once and then won't work at all now. I took the switch and unplugged the a/c side and plugged the heat side to it thinking that if that side worked for the a/c I thought I would work for the heat. But it still just hummed. So my question is what else could be wrong. The pilot light is lit and stays lit so it's not the thermocouple.
Was wondering if it was a capasitor?


DaleM
Posts: 385
Joined: Wed Apr 07, 2010 10:07 am

Sun Oct 07, 2012 8:23 pm

By swapping out switches you may have fried something. There is alot going on in that relay control box. Do you have a thermostat with a heat/cool selector switch on it?

Coolbluestreak
Posts: 3
Joined: Sat Oct 06, 2012 5:53 pm

Sun Oct 07, 2012 8:53 pm

no we do not have a thermostat that has the cool and heat it is on the furnance there is a cool/heat switch on the front on the furnace that is where we switch it.

DaleM
Posts: 385
Joined: Wed Apr 07, 2010 10:07 am

Wed Oct 10, 2012 12:25 am

Just being sure. Many people install new thermostats on 2 wire systems and when they don't work they have no idea what happened. There is a bad relay in that relay box someplace. There are 2 in there but it takes a little work to troubleshoot them out. I usually have several known good ones in my service truck. I normally replace one then the other when troubleshooting these systems, since it's faster than metering everything out. It's not a capacitor causing your problem.

Coolbluestreak
Posts: 3
Joined: Sat Oct 06, 2012 5:53 pm

Wed Oct 10, 2012 9:35 pm

I had a guy finally come out and look at it and he said that it was a relay, he hadn't worked with older units like this very much. It is from the late 90's, he works mainly on newer stuff. But he did say I had juice to some of the stuff and not to all to other wires. He was going to talk to his boss to find out what to do. Thanks


DaleM
Posts: 385
Joined: Wed Apr 07, 2010 10:07 am

Mon Oct 15, 2012 11:55 pm

Did you get your unit figured out? If not, I recently pulled out a 2 wire system and have the enitre relay box. Post a pic of yours to see if it matches what I have.

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