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BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 22466
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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My furnace will not start. There is a red LED that is

Customer Question

My furnace will not start. There is a red LED that is blinking with two blinks on the control module. It has a United Technologies 1018-204 module.
JA: Did you check the furnace's filters?
Customer: No. ZI donot see any filters and do not know where they would be on this furnace. It is a Nordyne MMHB-070ABHR-06 furnace. I just bought this house a few months ago. It was an unoccupied foreclosure.
JA: Do you plan on doing the work yourself?
Customer: Yes
JA: Anything else we should know to help you best?
Customer: I thought the problem might be the thermostat as I could not get all of the buttons to work. I replaced it with a new one of the same type.
Submitted: 8 months ago.
Category: HVAC
Expert:  BillyHvac replied 8 months ago.


My name is ***** ***** I will do my best to assist you. I am looking over your question now and will respond shortly.

Expert:  BillyHvac replied 8 months ago.

is the small exhaust fan running that is attached to the vent/exhaust pipe?

Customer: replied 8 months ago.
Customer: replied 8 months ago.
I do hear the wine of a transformer or something. I can use the manual switch to turn on the blower.
Expert:  BillyHvac replied 8 months ago.

ok that is the issue...the control box says "I sent power to exhaust fan" it is waiting for a air proving switch to close...which cant close if the exhaust does not run.

That is the issue...we need to see why the fan is not running...does it have power but is stuck? Does not have power?

Expert:  BillyHvac replied 8 months ago.

by fan...I mean small exhaust fan..not main blower

Customer: replied 8 months ago.
There are two red wires and two black wires going to the exhaust motor. I am getting about 28.5 to 28.8 volts ac from one of the red wires to the other three wires.
Expert:  BillyHvac replied 8 months ago.

Thank you...

now with exhaust running...connect the 2 wires you tested directly together..

Expert:  BillyHvac replied 8 months ago.

do the 2 black wires have 120v? keep the red and blacks separate

Customer: replied 8 months ago.
There are 4 wires Do you want me to connect the two red together? And the only voltage I already found was from the one red wire to the other 3.
Customer: replied 7 months ago.
The exhaust motor is not running either.
Expert:  BillyHvac replied 7 months ago.


as far as testing....only test red to red and black to black.

If you have zero volts black to black...we have no power to the exhaust fan motor.

Trace the black wires back to origin..does the black start from a control board?

Customer: replied 7 months ago.
There is no voltage across the black wires. Both black wires conect to a group of other wires that connects to the transformer and the control module.
Expert:  BillyHvac replied 7 months ago.

Thank you.

You have a bad control module. The control "thinks" it sent power is waiting for the air switch to close...but it actually did not send power.

You will need to replace the control

I am available for 30 days after the service is rated so if you need help just return here.


Customer: replied 7 months ago.
Correction, only one black wire connects to a group of wires. The other connect directly to the control module IND connection.
Expert:  BillyHvac replied 7 months ago.

correct.....IND = Inducer motor.

That wire should have 120v on it anytime the control is blinking that fault code.

If you turn power off to furnace and back on....does it start solid...then blinks?