Nordyne MGHA- 056ABFC-05 with 901994 relay switch box

Questions about repairs and parts for Nordyne furnaces, air conditioners and heat pumps for manufactured homes including Intertherm, Mac and Miller brands. Click here for Nordyne parts.

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Oscar Redding
Posts: 13
Joined: Tue May 26, 2009 10:45 pm

Robert, with your help believe I can handle it,. I have had some AC experience but am unfamielier with this control system. I'm not sure of the relay contacts, but will follow your instructions closely. Will get back with you tomorrow,. I am truly grateful for your help. Oscar
Oscar E Redding
Oscar Redding
Posts: 13
Joined: Tue May 26, 2009 10:45 pm

Robert, is the relay supposed to be energized? I don't think it is. Where does it get its voltage from? I'm getting 24v to the relay but not to the white wire that goes to the furnace. Oscar
Oscar E Redding
Oscar Redding
Posts: 13
Joined: Tue May 26, 2009 10:45 pm

I'm getting 24volts from c to w but not getting 24volts from W to Ground. Oscar
Oscar E Redding
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Robert
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Location: Tennessee

Hi Oscar,

I have no way of following the wires from here on to the gas valve, that is why an hvac tech may be needed.


IF you get 24vac across W and C, you should also get it from W to a ground.


The white wire comes from t-stat, if there is 24vac there, keep following it, testing at each connection until you lose the voltage or get to the gas valve.


You will need the experience to trace troubleshoot the low voltage circuit here or will need the hvac tech.


Without being there, I can't tell you exactly where to test. So if you do not have the experience to follow the wire from W to the gas valve testing each connection point for 24vac, then an hvac tech will be needed.


There is not any relays in that circuit to the gas valve. The white wire should go from t-stat to the control box terminal board W.


Then from bottom side of the W screw through the control box and down through molex connector to the heating control box.

Then straight to the gas valve.


So test for 24vac at transformer, then at W of t-stat, then W at control box, through connections/connectors and to the gas valve.

You should get 24-28vac at each to ground if all ok. If not, backtrack to where it was last at and problem is between them.


Thanks,
Robert
Some people are Humbly Grateful, while some are Grumbly Hateful.................... Which one are you ?
Oscar Redding
Posts: 13
Joined: Tue May 26, 2009 10:45 pm

Hi Robert. I appreciate your help. My circumstances are such that I have no technician that can help me at this time, so I have got to figure this out myself or go back to using space heaters. I believe that when I replaced the old control box, I must have connected up something wrong. I believe it has to do with the white and red wire s that I disconnected and wire nutted to the white and red wire oming from the furnace. The white wire came from the gas valve which was onnected to the thermostat . The white wire I connected to the new control box goes to the relay and the red wire I connected to goes to one side of the heat switch.. Some how these wires do not tie in to the t-stat on the new control box. I have two 24v transformers. One is in the furnace box and the other is in the control boc. since one side of the gas valve is connected to the lower trqansformer, I'm assuming that the other nside of the transformer has to make its way through the t-stat and back to the otherside of the transformer. I'm tenmpted to take off the nutted white wire and connecte it directly to the gas valve. This should at least fire up the gas valve. In short. I need to verify if I've got the white and red wite from the new control box to the correct white and red wire to the furnace. Thanks Robert for hanging with me. Sincerely. Oscar
Oscar E Redding
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Robert
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Location: Tennessee

Hi Oscar,

I've got a doc appt. to go to, but am looking for some info and should be able to get through this this evening.


Please bare with me and don't change anything yet.




Thanks,
Robert
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Robert
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Joined: Wed Feb 28, 2007 12:07 am
Location: Tennessee

Just a quick thought, be sure the furnace system switch is set to ON.


The relay is the reversing relay switching from cooling back to heating, forgot we were talking about a 2 wire, LOL.



With all wired as I stated earlier and all switches set correctly, it should work fine.


Be sure furnace switch is ON and control box switches are set to Heat and Auto.





Thanks,
Robert
Some people are Humbly Grateful, while some are Grumbly Hateful.................... Which one are you ?
Oscar Redding
Posts: 13
Joined: Tue May 26, 2009 10:45 pm

Robert, I dont believe my relay is switching to heat. Could you tell me where it gets its power? Which terminals and from which transformer? I am getting 24 volts from both transformers but my relay nmay be bad. I think I'm close to resolving this. Don't give up on me yet. Oscar.
Oscar E Redding
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