On a WaterFurnace Aurora Base Control, the red LED1 flash code names the condition that stopped the unit: 1 input fault, 2 high pressure, 3 low pressure, 4 freeze detection 2, 5 freeze detection 1, 7 condensate overflow, 8 over/under voltage, 11 freeze sensor error. Read the code first, then check the circuit it names.
What the Aurora Base Control flash codes are
The Aurora Base Control (ABC) is a WaterFurnace control board. When it detects a fault, its LED1 flashes red a set number of times, and the number of flashes is the fault code. WaterFurnace publishes the code list in its Aurora Base Control guide, AG1562EW (the LED1 flash-code table on p.9 and the Control Board Troubleshooting Steps on p.16).
This article lists eight of those codes: 1, 2, 3, 4, 5, 7, 8 and 11. The guide contains other codes that we have not reproduced here. If your LED shows a count that is not on this list, use the guide for that code rather than guessing from this page. The same applies to any WaterFurnace unit that does not use the Aurora Base Control: other Aurora controls and other WaterFurnace lines have their own manuals and their own code tables.
Fault codes 1, 2, 3, 4, 5, 7, 8 and 11 (AG1562EW, pp.9 and 16)
- 1, Input Fault: both the O and W inputs are present at the same time.
- 2, High Pressure: system pressure exceeded 600 psi. The guide gives this figure for R-410A.
- 3, Low Pressure: the low pressure switch has opened. The guide notes this may indicate a loss of system charge, a system restriction or a frozen heat exchanger.
- 4, Freeze Detection 2: the guide marks this code as future use.
- 5, Freeze Detection 1 (coax): low or no water flow, low system charge, or a faulty TXV in heating mode.
- 7, Condensate Overflow: water in the drain pan has risen and touched the spade terminal.
- 8, Over/Under Voltage Shutdown: control voltage is, or has been, outside 18 to 30 VAC for more than 15 minutes.
- 11, Freeze Detection Sensor Error: the freeze detection sensor reading is out of range.
What each group of codes points to
Pressure faults (2 and 3). Code 2 is a high-pressure condition and code 3 is a low-pressure condition. The guide ties code 3 to the low pressure switch opening and says it may indicate a loss of system charge, a system restriction or a frozen heat exchanger. A code on the display is a symptom, not a verdict on the switch. Connect gauges and confirm actual system pressures before you decide that a switch or sensor is the problem, and remember that refrigerant work is for certified technicians only. The 600 psi figure in the guide is stated for R-410A; for a unit on a different refrigerant, use that unit’s own literature.
Freeze faults (4, 5 and 11). Code 5 is Freeze Detection 1 on the coax, and the guide gives its three causes above. Code 4 is listed in the guide as future use. Code 11 is a different entry: the guide describes it as the freeze detection sensor being out of range, not as a water flow, charge or TXV cause. Read which of the two codes you have before you order parts. For the causes behind code 5, see our companion article on WaterFurnace fault 5 and fault 7.
Condensate overflow (7). The guide describes this as condensate water in the drain pan filling up until it touches the spade terminal. The code tells you the pan has filled to that point. It does not say why the pan filled; that is a question for the drain path and the unit installation.
Voltage (8). The guide gives a specific window: the control voltage is, or has been, outside 18 to 30 VAC for more than 15 minutes. It does not name a failed component as the usual cause, and neither do we. Measure the control voltage at the board and work upstream from what you measure.
Input fault (1). The control sees both O and W present. Look at the thermostat or controller wiring and settings that feed those two inputs.
How to work a fault code
- Confirm the control. The code list above is for the Aurora Base Control, per AG1562EW. Check the board label and your unit’s literature before you use it.
- Record the code before you clear anything. Count the LED1 red flashes, write the number down, and note whether the unit is calling for heating or cooling. Write it down before you reset.
- Match the number to the guide. Use the list above or pp.9 and 16 of AG1562EW. If the count is not on the list, read the guide.
- Check the condition the code names. Pressure: read actual gauge pressures. Freeze: confirm water flow and look at the sensor and its wiring. Condensate: look at the drain pan and the spade terminal. Voltage: meter the control voltage at the board. Input: check the O and W wiring.
- Isolate before you touch anything. Remove power and apply your site’s lockout/tagout procedure before opening the control section or handling wiring.
- Fix the condition, not just the code. A fault that is still present will set the code again after a reset.
- Reset as your manual directs. Reset methods are covered in our article on how to reset a WaterFurnace lockout.
- Watch the next cycle. If the same count returns, the condition has not been cleared. If a different count appears, start again from step 3 with the new code.
Parts involved
| Component | Role in this issue | Where to find it |
|---|---|---|
| Aurora control board | The board that runs the LED1 flash codes. Listed with several board numbers; confirm yours against the unit label and literature. | 17X553-12 — WaterFurnace AURORA Board NXW/WC/NDW RES/COM |
| Freeze protection thermistor | Relevant to the freeze codes (5 and 11). The guide does not say which sensor model your unit uses. | 12P560-06 — WaterFurnace Thermistor Freeze Protection Yel 36" |
| Freeze sensor thermistor | A second listed freeze sensor. Fit depends on the unit; the title gives a clip size only. | 12P564-03 — WaterFurnace Freeze Sensor Thermistor 10k 7/8"Clip |
| Condensate harness | Listed as an Aurora condensate wire harness. Relevant to code 7 only where your unit uses it. | 11P826-04 — WaterFurnace Wire HRNS-AURORA-P3 Condensate 120 In AMP41802 |
| Pressure transducer | Listed as a pressure transducer. The guide excerpt we used does not say which device feeds codes 2 and 3 on each model. | 19P9000-01 — WaterFurnace (& w/19P555A02) Pressure Transducer |
| Thermostatic expansion valve | A faulty TXV in heating mode is one of three causes the guide lists for code 5. Many TXVs are listed by tonnage and model. | WaterFurnace Replacement Parts |
Scope: This article covers the WaterFurnace Aurora Base Control as described in AG1562EW (flash-code table p.9, troubleshooting steps p.16). Aurora Advanced and other Aurora controls, Versatec and other WaterFurnace lines, and codes not listed above have their own documents. Check yours.
Before you order
Confirm your unit’s exact model and serial number from its nameplate before ordering, and note the board number if the control is the suspect part. Search the part number in our site search, or browse the WaterFurnace replacement parts collection. We also list parts by unit model; search your model number to find its collection, and see our overview of Johnson Controls and YORK geothermal parts made by WaterFurnace if your nameplate carries a different brand. See our guide on finding the correct part from the model and serial number, or contact us at help@totalhvacparts.com and we will help confirm fit.
Frequently Asked Questions
What does a flashing red light on a WaterFurnace Aurora control mean?
On the Aurora Base Control, LED1 flashing red is a fault code. The number of flashes identifies the fault, such as 2 for high pressure or 3 for low pressure (AG1562EW, pp.9 and 16). Count the flashes and look the number up in the guide.
What is WaterFurnace fault 3 (low pressure)?
Fault 3 means the low pressure switch opened. The guide notes it may indicate a loss of system charge, a system restriction or a frozen heat exchanger. Confirm actual pressures with gauges before replacing anything, and use a certified technician for refrigerant work.
What is WaterFurnace fault 2 (high pressure)?
Fault 2 means system pressure exceeded 600 psi on an R-410A unit, per the Aurora Base Control guide. Read gauge pressures and find what raised them before you reset the control.
What does WaterFurnace fault 8 mean?
Fault 8 is an over/under voltage shutdown. The control voltage is, or has been, outside 18 to 30 VAC for more than 15 minutes. Measure the control voltage at the board and trace the cause upstream.
Sources
- WaterFurnace Aurora Base Control guide, AG1562EW (flash-code table p.9, troubleshooting steps p.16)
- Live product titles for the parts listed above, as shown on each product page
WaterFurnace heat pumps involve line voltage, 24 V control circuits, pressurized refrigerant and rotating equipment. Service should be performed only by qualified personnel, following the manufacturer’s manual for your unit and your facility’s lockout/tagout procedures.