How To Fix Coleman Furnace Twinning Error

Coleman furnace has a built-in self-diagnostic feature. If a problem occurs, your furnace will send you an error code. A rapid red flash indicates Coleman furnace twinning error. Here we have a solution to solve that problem.

You need to understand the basics of how twinning furnaces work, so you know what to look for when there is something wrong.

Some basic rules need to be followed to accomplish twinning Coleman furnaces.

  • You need to have identical twins.
    • same model, BTU, CFM capacity
    • all motor leads must be on the same taps
    • all control board settings must be the same
  • Boards must be identical part numbers.
    • or the boards will not communicate properly with each other
  • The power to the furnaces must be off the same buss bar in the fuse or circuit breaker panel.
  • Twinned furnaces must be applied on a common return and supply duct system.
  • Isolation relays need to be installed on the “slave” furnace to isolate transformers.
  • Only PSC  motor equipped furnaces can be twinned
    • Furnaces with ECM motors cannot be twinned

When you replace a control board on twinned furnaces, don’t forget to replace the other board at the same time. Also, make sure that the new board is the same as the one you are replacing.

Twinning Coleman furnaces is easy and can be done without any additional controls. The furnaces will be twinned by running a single wire between the twin terminal on each board.

When successful, twinning of furnaces will work very well and provide higher heat capacity for your home. Unsuccessful twinning will give you an error.

Here is what to do when Coleman furnace twinning error:

Was the control board replaced recently? Were any of the dip switches moved accidentally? This error on a single unit is generally caused by the 24volt system being out of phase (wires backward for one reason or another).

The transformer could also cause Coleman furnace twinning error, but I would look at the wiring. The wiring could have been suspect from the beginning and finally got to your transformer, and that’s why you are seeing this error now.

The 24volt wires from the secondary side of the transformer must be in the EXACT Sec 1 and Sec 2 positions. Carefully read the markings on the board and wiring diagram to make sure he did not switch them up.

Fixing the Coleman furnace twinning error is not a DIY task. If you don’t know what you’re doing with your furnace, you could cause yourself more problems. Call a professional HVAC technician to have your furnace fixed fast.

About Mas Broto

Have been in the heating and air conditioning (HVAC) industry for over 20 years. He is person that will grow and thrive to learn more about the HVAC industry throughout his career. Mas Broto is also a blogger, who's dedicated to bringing you the best knowledge to get ahead in the game of life.