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I have 1996 Nordyne MMHA-090ABHR-05. The Serial # is MMH9603-00314. The blower motor and outside Coleman A/C unit run constantly unless I shut it off at the breaker box. The furnace has a Heating/Cooling swicth on the front of it just like the thermostat. Both are obviously set to cooling. The only thermostat wires hooked up are Red and White. The Yellow, Green and Blue are wrapped around and not used. I have had two service techs out before but no help. One said it was the stat. I replaced the Lux Programable stat with a Honeywell 511. Same thing. Still runs. The guy at Menards said I needed the old style Round stat. because it wasn't programable. I switched that the other day. It Still runs.The other Tech said one of the $30.00 each relays in the box behind the Heating /Cooling swith was bad. I replaced both just to be sure because he didn't know which one it was for cooling. Still Runs all the time. Then he said the R & RC need to be jumped. Tried that too. Still runs all the time.The sales person at Illinois Mobile Home Repair said it was the Fan switch. I replaced that too. It still runs all the time. I called Honeywell tech support today and the nice person could hardly speak English. He suggested to call a local mobile home repair place nearby. This months electric bill is going to be outrageous. Is this something simple I can do myself, or do I need to call a pro ? Cha Ching Cha Ching. Thanks in advance Guys !!
Mark

Hi Mark,

Set t-stat to HEAT and AUTO. Set furnace switches to COOL and AUTO. Then set t-stat temp lever where you want home to be temp wise.


With all you changed, that should take care of it IF you have a t-stat compatible to 2 wire systems.



Thanks,
Robert

Robert,

It works PERFECTLY. Unbelievable. Two service techs in person here in the Chicago area look at it and didn't have a clue.Two sales people that didn't know their _ss from a hole in the ground try to diagnose it. Over $125.00 in fuel and parts NOT needed. An unkown amount of money wasted to the electric co. from the wife "just letting it run". Then you, from the comfort of your home in Tennesee, diagnose it sight unseen, on the computer, and it works. You are a GENIUS.

THANKS A MILLION BUDDY !!

Mark

Hi Mark,

You're very welcome, happy to help and glad it's working properly . Thank you for your kind words. Most people have trouble diagnosing or understanding a mobile home hvac 2 wire system if they have not been taught or trained in them.


The only thing that EVER changes is the furnace switch, cool for summer and heat for winter.


Take care and best wishes,
Robert