Nordyne Gas Furnace: G6RC

Re: Flashing Code 1

Code 1 = Limit switch open

If the limit control opens, the burners will be de-energized and the air circulation and vent blower will be turned on until the limit closes.

The diagnostic light code for this is one short flash followed by a pause.

► All limits are wire in series (Primary Limit, Manual-Reset Vent Limit, Manual-Reset Flame Rollout(s), Manual-Reset Blower Limit).

CHECKOUT:

1. Check the Limit Circuit

• Re-start the furnace with a call for heat.
  • Furnace starts and runs normally with no fault codes → Step 2. Check Temperature Rise 
  • Furnace immediately flashes Code 1 and starts the inducer and blower:
    • On the 9-pin plug at the furnace control board check for 24VAC between Pin #8 (Blue) and "C", then between Pin #3 (Blue) and "C".
      • Power on Both Pins + Code 1 = Bad Control Board
      • Power on One Pine Only + Code 1 = Open Limit Circuit
        • Check for 24VAC from both sides of each limit to "C".
          • No Power On Either Side = Another limit in the series tripped - Keep checking
          • Power on Both Sides = Limit OK
          • Power On One Side Only = Tripped Limit
            • Manual-Reset Roll-Out Limit(s) ⇒ Check Heat Exchanger
            • Manual-Reset Blower Deck Limit (Select models only) ⇒ Check for a Bad Blower Motor
            • Auto-Reset Main Limit →​​​​​​​ Step 2. Check Temperature Rise  
            • Manual Reset Inducer Limit (Select models only) →​​​​​​​ Step 2. Check Temperature Rise 

2. Check Temperature Rise

• Start the furnace with a call for heat.​​​​​​​
• Check and record the return air temperature near the furnace (at the filter if possible) with the blower on.
• Check the supply air temperature (in a straight duct run near the furnace) as the furnace operates.
• Compare the actual temperature rise to the rated temperature rise on the furnace nameplate. (typically 40 - 70 deg.)
  • Temperature Rise Near or Above Maximum → Step 3. Check Air Filter
  • Temperature Rise Below Maximum + Code 1 ⇒ Suspect Bad Limit

3. Check Air Filter

• Remove the air filter and recheck the temperature rise.
  • Temperature Rise Drops into Normal Range = Clogged, Restrictive or Under-Sized Filter
  • Temperature Rise Still too High → Step 4. Check Gas Pressure

4. Check Gas Pressure

• Check the manifold gas pressure.
  • Natural Gas = 2.5" w.c. minimum to 3.5" w.c. maximum
  • LP Gas = 9" w.c. minimum to 11" w.c. maximum
• Pressure Below Maximum → Step 5. Check Blower Speed
• Pressure Above Maximum ⇒ Adjust Gas Pressure & Re-check Temperature Rise

5. Check Blower Speed

• Check the blower motor speed wire attached to the "Heat" output of the control board.
  • Red = Low
  • Orange = Med Low
  • Blue = Med Hi
  • Black = Hi
• If possible, increase the Heat blower speed and Re-Check Temperature Rise

6. Check Duct Static Pressure

• Check the return static pressure (between the filter & the blower).
• Check the supply static pressure.
  • High Duct Static = Above 0.5" w.c.
    • High Return Static + Low Supply Static = Restricted Return Ductwork or Filter ⇒ Check the static pressure on both sides of the air filter.
      • Drastic difference = Clogged, Restrictive or Under-Sized Filter
    • Low Return Static + High Supply Static = Restricted Supply Ductwork
    • Low Supply Static + Low Return Static = Clogged Evaporator Coil, Blower Wheel, Recoup Coil or All Three