Nordyne Miller CMF 80 CONV been dead for a month...anyone he

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Nordyne Miller CMF 80 CONV been dead for a month...anyone he

Postby krissypee03 » Tue Feb 26, 2013 1:00 am

help me please. We lost heat for the first time in December, found out to be a broken ceramic coil on the ignitor. We found it bought it and installed it with no other issue. My husband is a mechanic, so he likes to tinker and thanks to YouTube this was an easy fix. When we first installed we ran into a minor glitch where the new igniter wasn't sitting correctly but the blink codes told us that there was a "false flame" code and we knew what to look for to fix. Problem solved.

here's a little history.
we live in a mobile home, circa 1970s
When we moved in around 2000, the furnace was the first thing we replaced. Nordyne Miller CMF 80 CONV. I'd say install date had to be early 2001. We kept up with routine maintenance and thought we were good.
This is a mobile home furnace, natural gas (no propane tank) closet installation in the inner hallway of our home (dead center of the house, not an outside wall)
We normally keep the heat around 68, nights and during the day low 60s.
We live in Taunton MA, deep in the heart of New England

Everything worked fine for a few weeks. On January 26 (a Saturday) I came home from errands and thought it was a little chilly but it was snowing outside. When he got home from work he spoke up about it being chilly so I investigated. Thermostat was set at 68 but house was already reading at 52 degrees. I never heard any bang or thud or pop, and I do remember hearing the blower while I was putting away things that afternoon but can't remember when I stopped hearing it.

We replaced the thermostat first, since we had the original old lever style that was here when we moved it, we upgraded to a very low end compatible digital thermostat by Hunter, red and white wire. No go, so we started troubleshooting, still sure it was something cheap. He brought home his multimeters from work, and a bunch of other testers so he could try to sort it out. We have power everywhere, and for giggles he unplugged the lower half of the furnace, the heating part, from the receptacle since a friend had a similar problem and after 2 weeks they finally sorted it out to a 2 dollar part by doing the same thing. When we plug it it to an extension cord it runs, obviously we've broken the connection to the blower motor when we do this, but we hear the furnace start, the ignitor spark and gas turn on....everything works fine except the blower motor obviously can't turn on.

We replaced the receptacle but it did nothing. After 2 weeks we gave up trying to figure it out and called and HVAC specialist. He came to the house, nearly electrocuted himself since he was sure we didn't have power going to the blower motor and told us it was a bad blower motor. He advised us that it was an easy fix for someone that was good at fixing things, so he was confident we had it under control. Installed the motor he suggested with nothing new to report, still no furnace. The motor came with it's own capacitor if that helps.

Since then our "what if's" have led us to replace the hot surface ignitor board, the fan limit control switch, the limit control and transformer. tonight he noticed that even though his meters show he has 220 coming out of that receptacle when we plug it in to a little light cube we have and use to test outlets, there is no power, even when we set the door switch to think the door is latched and ready to go. Yes, we've tested the door switch and everything works there. We even replaced the breaker in the main box in the house that controls the furncace, thinking we were on some sort of brown power off that breaker and figured it couldn't hurt at this point. We get no blink codes at all,, and haven't even seen evidence that we're going to see those flashing red lights anytime soon.

We are really at a loss. If there's anything anyone can offer as advice we'd be willing to try before we give up and drop the 1500 on a new one. I can probably answer any other questions that I might have missed if need be. Thanks for your help. It's been 3 blizzards two marathon power failures and a month solid without a furnace. My gas and electric bills thank you...
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- Nordyne Miller CMF 80 CONV been dead for a month...anyon

Postby Freon » Tue Feb 26, 2013 3:03 pm

I'm sorry to read about your problems. Sometimes throwing parts at a problem hoping one will stick isn't the best approach. However an HVAC tech may do that because of the time involved learning the real cause of the problem.

Let's start from the beginning. First, does your furnace have a spark type ignitor that lights a small pilot light first, then the main burners second. Or do you have a hot surface ignitor (HSI) that glows red hot for about 10 seconds.

Have someone call for heat at the thermostat while you sit and watch the furnace. I need you to write down exactly what you SEE and HEAR happening as the furnace tries to light. Usually you should hear a small motor run that will induce the proper draft for the combustion chamber. This process could take 30 seconds. Then the ignitor will start to either glow (HSI) or spark (pilot light). After maybe 10 seconds of glowing the gas valve should open. There's usually a noise as the gas valve opens. Then immediately the burners light. Shortly thereafter the main house blower will start and all will run until the set temperature of the thermostat is satisfied.

Let us know what happens.

Do not use dashes, slashes or question marks in your post.

Here is some good DIY troubleshooting -
w w w dot nordyne dot c o m slash Literature slash 067a.pdf
w w w dot nordyne dot c o m slash Literature slash 708062b.pdf
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