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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have a nordyne furnace model MMHA-066AA HR-01. HAVE POWER

Customer Question

I have a nordyne furnace model MMHA-066AA HR-01. HAVE POWER (120 V) COMING IN WITH 24 V COMING OUT OF TRANSFORMER. NO LIGHTS ON MODULE . NO POWER GOING TO IGNITER.MY QUESTION IS DOES THIS SOUND LIKE MODULE IS BAD AND NEEDS REPLACED?
Submitted: 1 year ago.
Category: HVAC
Expert:  Phil replied 1 year ago.

Hello, there is about a 50% chance its a bad module, if its not a bad module, it could be an open door switch on blower door, or a failed high temperature safety cut out switch, or a bad pin connection in one of the connectors.

Please attach a well focused, close up photo of the wiring diagram glued inside the service panel, the picture needs to be taken from straight on, in very good light.

You can use the paper clip- icon at the right end of the tool bar at the top of this dialog box to attach it here. ,Include a picture of the thermostat wire connections to the printed circuit board in the same area.

If there is no paper clip-icon, look for the '+attach files' link at left of your send button.

I can mark it up with trouble shooting instructions.

Customer: replied 1 year ago.
THAT'S A PROBLEM AS THERE IS NO DIAGRAM ANY WHERE ON IT. I'VE BEEN TRYING TO FIND ONE ONLINE TOPRINT OUT BUT HAVEN'T HAD ANY LUCK YET
Expert:  Phil replied 1 year ago.

If you can send me 2 pictures of the furnace with both front panels removed that will help.

One picture of blower area and one of the gas valve and burner compartment, the entire compartment so I can look for the high limit and flame roll out switches.

Next do this heat stress test on the printed circuit card.

Use a hair drier to slowly and gently warm the card to 120F (warm to the touch but not hot and not over140F)... if you get any change in behavior that means the card is bad...

A micro crack has opened in the printed circuit at a solder joint, or inside its CPU in that case .... or a short circuit has developed as the card expanded when you heated it.

Constant expansion and contraction as these electronics heat and during their duty cycles over the years is what wears these cards out.

It is also a good idea to replug all of the connections in the unit,that burnishes any oxidized terminal connections and will sometimes solve the problem, especially at the printed circuit card and in any sensor molex connectors. Do that with the power off to the unit of course.

Customer: replied 1 year ago.
OK II'M GOING TO HEAD OVER TO THEIR PLACE AND WILL SEND PHOTOS ASAP.AGAIN THANKS. THESE POOR PEOPLE ARE IN THEIR 80'S AND CAN'T HANDLE THE CHILL. I'M DOING THIS AS A GOOD DEED CAUSE THEY CAN'T AFFORD TO CALL A TECH. I'M NOT EVEN CHARGING THEM THE $28 OR ANYTHING ELSE FOR THAT MATTER.
Expert:  Phil replied 1 year ago.

You are a very good man.

The bigger picture is their overall heating costs. If they can get mattress warmers for the beds they can run the heat down to 55F at night.. that will help a lot. then they can use a portable electric heater in just the one room they occupy during the day.

That can cut their costs dramatically after get the furnace fixed.

These new electronically controlled furnaces are an ongoing expense that they will do well to live without as much as possible.

I will wait for the results of the heat stress test, and the photo's.

Customer: replied 1 year ago.
THANKS I'LL PASS THOSE TIPS ON TO THEM.
ITS GOING TO TAKE ME ABOUT 45 MIN. TO GET THERE.
Expert:  Phil replied 1 year ago.

That works.