Nordyne M1M Low Flame Blinking Yellow Light

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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ckamin
Posts: 2
Joined: Thu Oct 15, 2009 3:30 pm

Hi All,

I have a problem with this unit. It is a three/four year old M1M with A/C. What happens is, I can hear the combustion fan run and the ignitor lights up, there is a blue flame, the yellow light blinks continuously and the flame goes out in about 30 seconds or less. The main blower runs after a moment or so before the flame goes out. It then starts the routine again in a few minutes. The flame seems small and not intense enough to be right. There seems to be just about 24 volts to the Gas Control Valve while the flame is present. Before I start trying to take a guess, I wanted to run this one by a few more knowledgeable people. The stack seems clear BTW. No real bad soot inside either. The Gas Stove works just fine, so there is probably gas available. I don't have a manometer handy, so can't say for sure what the pressure is. The unit ran fine before the beginning of the last A/C season.

I'm wondering what to look at or fix or replace. I'm looking seriously at the gas control valve. It's a Robertshaw 7200 DERC. I think it might be that it is designed to start out with a lower flow and it never makes it to the higher flow level. The Ignitor glows white hot and the flame lights when gas is present. The flame seems small and much lighter than I would expect. I'm also thinking that there might be a sensor near the ignitor, but can't really tell unless I start tearing this thing down. The system has not been used this season for heat and this is the first time it was started up in heat mode.

My main problem is I'm about 100 miles away from the unit at the moment, so I don't have it in front of me for exact model numbers.

Some history about the system. It has been a problem since day 1. The A/c unit had to be replaced right after installation, since it did not operate properly. It had a leak in the A/C system as well. Before the beginning of this past A/C season, the thermostat was replaced and the Capacitor on the compressor was replaced. The heating part of the system worked fine for two seasons. The system appeared to work fine after the thermostat was replaced. It was done since the old unit was using batteries and needed frequent replacement. The new one uses the "common" wire and runs off of the 24 volt supply, rather than batteries.

I would also need a resource to find the actual part numbers of the parts other than the control valve.
furnaceman
Posts: 23
Joined: Fri Oct 09, 2009 11:07 am

hi,
since u don't have the exact model number in front of us, lets start with the fact you said it has an igniter, usually when a unit has an hsi (hot surface igniter) it also has what is called as a flame sensor. This is usually a "metal rod" about the thickness of pencil lead. It will be mounted so that when the burner is lit, it will be in the the flame. Its purpose is to verify, ignition, if it senses flame, it relays that to the control module, and gas valve stays open tilol t-stat is satisfied. if this sensor doesn't sense a flame, flame rectification won't be sensed, and control module will shut down the ignition process to prevent gas from flowing when no flame is present. It will retry a few times, then go usually go into hard lockout.
Based on what you stated it sounds like this is what might be happening.
You can clean the flame sensor off with a green scratch pad ( like your wife uses in the kitchen).
Shut off furnace, locate and remove sensor, wipe till it shines, then re-install, turn power back up and call for heat and see if that fixes problem.
You will have 2 excuse my rather lengthy babbling, been a busy day, lots ofr service calls, pretty tired now, will check back later.
ckamin
Posts: 2
Joined: Thu Oct 15, 2009 3:30 pm

Hi,

Thanks for the reply. It actually appears that the ignitor and flame sensor are built into the same unit. I was able to locate some diagnostic information for the unit. I believe it is an M1MB070ABW. It is HSI ignition with a spiral wound ignitor. No pilot light. What my issue is that the diagnostics don't address the blinking yellow light, except to mention is is a low flame condition. Is it the sensor or the gas control valve? Sort of like the chicken or the egg. I followed the sequence of operation diagrams and descriptions, and the unit appears to work as it should, UNTIL the yellow light starts to blink and it shuts down the main blower after a short time. The flame just never seems to go full on. If the flame did not go on in the first place, I'd be looking at something else. However, there appears to be no real clear winner here. If I had to take a guess and throw some parts at it, I'd be replacing the ignitor/flame sensor AND the Gas Control Valve. I suspect the control valve at the root of it, since I believe it is a staged opening type valve, where it opens a little and then full on after a short time. The flame never appears to be full on, so that's my reasoning. I tend to think that the sensor and control board are telling me the truth. If there is anything else that comes to mind, please let me know. I'll probably be ordering both the valve and the sensor/ignitor for replacement anyway, just so I don't have to waste too much time for further diagnosis and drag this out for a couple of weeks.

I can certainly understand how busy you guys are these days. It's the beginning of the heating season and everyone seems to notice that their system doesn't want to work right when they turn it on for the first time this season.
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Robert
Moderator
Posts: 6413
Joined: Wed Feb 28, 2007 12:07 am
Location: Tennessee

Hi,

Quickest solution to finding the problem is to test input and manifold gas pressures first.

IF ok, then inspect burner orifice and orifice spud for blockage (spider/web).

Those are the two most common for what you're describing.

Mobile home furnaces are half and half on having flame sensor or it being built into HSI.

Yours is built into HSI.

If ordering info needed, let me know.



Thanks,
Robert
Some people are Humbly Grateful, while some are Grumbly Hateful.................... Which one are you ?
burnertech
Posts: 2
Joined: Tue Nov 03, 2009 7:30 pm

On these miller units, the flame rectification comes from the ignitor not a seperate flame sensor, so what needs to be done is to test the signal by remeoving the ground wire at the control board and testing microamp signal. It needs to read above 1.0ua to stay lit. if it is under that or below 1.5 then pull burner out , check the orifice for cob webs, if still ok and gas pressure is ok, try bending the ignitor tip into the flame more by the bracket. If no luck, change ignitor.
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