Armstrong furnace 13 flashes: Low line voltage
Thirteen flashes means the incoming line voltage is too low. This is a supply problem outside the furnace, and replacing furnace parts will not fix it.
Applies to: Allied Air Enterprises A80UH1E and 80G1UHE gas furnaces with the -02 integrated control, sold as Armstrong Air, AirEase, Concord and Ducane.
What it means
The control monitors its own supply voltage and reports when it falls below the acceptable range. That is worth having as a distinct code, because low voltage produces symptoms that look like component failures: motors draw more current and run hot, relays chatter or fail to pull in, and controls behave erratically. Without this code, a furnace on a sagging supply would present as a series of unrelated faults. With it, the diagnosis points outside the furnace entirely — to the circuit feeding it, the panel, or the utility supply.
Most common causes
- A utility supply problem, particularly during peak demand or a brownout.
- An undersized circuit feeding the furnace.
- A loose or corroded connection in the supply, causing voltage to sag under load.
- A shared circuit with a large intermittent load on it.
- A long cable run with excessive voltage drop.
- Running from a generator with poor voltage regulation.
How to diagnose it
- Note whether other appliances show symptoms — lights dimming when a large load starts is a useful clue.
- Note whether the fault correlates with time of day, which would suggest a utility or peak-demand problem.
- Note whether the furnace has been running on a generator, which is a common and easily forgotten cause.
- Note whether the fault appeared after electrical work in the house.
- Recall the stored history — repeated low voltage codes interleaved with other faults suggest the voltage is the root cause of all of them.
How to fix it
- This needs an electrician rather than a heating technician. The furnace is reporting a fault it did not cause.
- Have the supply to the furnace checked for loose connections and adequate conductor size.
- If the problem is at the utility side, report it to the supply company.
- Do not have furnace components replaced before the supply has been checked. A new motor on the same sagging supply will fail the same way.
Notes
This is the furnace code most likely to be reporting a problem elsewhere in the building. It is worth acting on even if the furnace is otherwise working, because sustained low voltage shortens the life of every motor in the system.
Related
All codes for this manufacturer
Armstrong Air, AirEase, Concord and Ducane furnace codes — every code, with what differs between models.