On a WaterFurnace Aurora Base Control, fault 5 is Freeze Detection 1 on the coax, and the guide lists three causes: low or no water flow, low system charge, or a faulty TXV in heating mode. Fault 7 is Condensate Overflow: water in the drain pan has risen and touched the spade terminal.
What fault 5 (Freeze Detection 1) means
Fault 5 is one of the red LED1 flash codes on the Aurora Base Control. The guide, AG1562EW (p.16), labels it Freeze Detection 1 and ties it to the coax. It lists three possible causes: low or no water flow, low system charge, or a faulty TXV in heating mode.
Those three causes sit in different circuits. Water flow is a loop-side condition. Charge is a refrigerant-side condition. The TXV is a refrigerant-circuit component that the guide names only for heating mode. The code does not tell you which of the three you have. It tells you the control reported Freeze Detection 1 on the coax. Your job is to work through the three in a sensible order, starting with the one that needs no gauges: whether water is moving.
Two neighboring codes are easy to confuse with it. Fault 4 is Freeze Detection 2, which the guide marks as future use. Fault 11 is Freeze Detection Sensor Error, meaning the freeze sensor reading is out of range. Read which of the two codes the LED shows before you choose what to check.
What fault 7 (Condensate Overflow) means
Fault 7 means condensate water in the drain pan has filled up and touched the spade terminal (AG1562EW, p.16). The control reads that contact as an overflow and reports it. The pan has to be full enough to reach the terminal, so the useful question is why the pan filled.
The guide excerpt we worked from does not list causes for fault 7. We do not list any either. Look at the drain path from the pan outward, then look at the spade terminal and its wiring. Both are visible checks that need no meter.
Sorting the causes of fault 5
The three causes in the guide split cleanly into water-side and refrigerant-side. Low or no water flow is water-side, so it is the one you can check with eyes and hands: is the pump or flow center running, are the valves open, is water moving through the coax circuit. Low system charge and a faulty TXV are refrigerant-side, and both need gauges, temperatures and a certified technician.
The guide names the TXV only for heating mode. That detail matters when you record the fault. Note whether the unit was in heating or cooling when the code set, along with the code number and the date. If you later call us or the manufacturer, the mode, the model number and the serial number are the three facts that save the most time.
Do not treat the three causes as a ranking. The guide as we read it gives no ordering by likelihood, and we do not add one. We start with water flow only because it is the quickest check to make and because the guide lists it first.
How to check fault 5
- Confirm the control and the code. The flash codes in this article are for the Aurora Base Control. Count the LED1 red flashes, confirm it is 5, and write it down.
- Rule out code 11. A freeze sensor error is a different code. If the count is 11, use the guide's entry for it rather than the fault 5 causes.
- Isolate power before opening the unit. Apply your site’s lockout/tagout procedure before you work inside the cabinet.
- Check that water is moving. Confirm the pump or flow center is running, the loop valves are open and flow is present, following your unit’s IOM. Low or no water flow is the first cause the guide lists.
- Check the heating-mode refrigerant side. If water flow is normal, the other two causes are low system charge and a faulty TXV in heating mode. Both need gauges and a certified technician.
- Check the freeze sensor and its wiring. A freeze fault can only be judged if the sensor is reading properly. Inspect the sensor mounting and wiring.
- Reset only after the cause is fixed. See how to reset a WaterFurnace lockout for the reset methods and the timing difference between manuals.
How to check fault 7
- Isolate power. Apply lockout/tagout before opening the cabinet.
- Look at the drain pan. Is there standing water in the pan, and is it high enough to touch the spade terminal?
- Follow the drain path. Trace the condensate drain from the pan out through the piping and trap. A drain that cannot carry water away is one way a pan can fill.
- Inspect the spade terminal and harness. Check the terminal and the condensate wiring for damage or contact with water.
- Dry the pan and restore the drain. Do this before any reset, or the fault will return.
- Reset and watch a cycle. If fault 7 returns, the pan is filling again. Stop and find the source.
Parts involved
| Component | Role in this issue | Where to find it |
|---|---|---|
| Freeze protection thermistor | Relevant to the freeze codes (5 and 11). The guide excerpt 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. The title gives a clip size; confirm fit for your unit. | 12P564-03 — WaterFurnace Freeze Sensor Thermistor 10k 7/8"Clip |
| Condensate harness | Listed as an Aurora condensate wire harness. Relevant to fault 7 where your unit uses it. | 11P826-04 — WaterFurnace Wire HRNS-AURORA-P3 Condensate 120 In AMP41802 |
| Condensate bulkhead connector | Listed as a condensate bulkhead connector. Confirm against your unit. | 12P504A01 — WaterFurnace Condensate Bulkhead Connector |
| Thermostatic expansion valve | A faulty TXV in heating mode is a listed cause of fault 5. TXVs are listed by tonnage and model. | 33P628-01 — WaterFurnace TXV TR6 3-TON ADJ W/BLD IC Switch EL24" |
| Per-model parts | We list parts by WaterFurnace unit model. Search your model number for its collection, for example the NDV049G111CTL0AA collection. | WaterFurnace NDV049G111CTL0AA Parts |
Scope: This article covers fault 5 and fault 7 on the WaterFurnace Aurora Base Control, as listed in AG1562EW (p.16). Other Aurora controls and other WaterFurnace lines have their own documents. The TXV listed above is one of many; match yours by model and the unit’s literature, not by this article.
Before you order
Confirm your unit’s exact model and serial number from its nameplate before ordering. Search the part number in our site search, or browse the WaterFurnace replacement parts collection. For the full code list, see our article on WaterFurnace Aurora Base Control fault codes. To confirm fit, contact us at help@totalhvacparts.com with the model and serial number.
Frequently Asked Questions
What causes WaterFurnace fault 5 freeze detection?
The Aurora Base Control guide lists three causes: low or no water flow, low system charge, or a faulty TXV in heating mode (AG1562EW, p.16). Check water flow first, then use gauges for charge and the TXV.
What does WaterFurnace fault 7 condensate overflow mean?
Condensate water in the drain pan has filled up and touched the spade terminal (AG1562EW, p.16). Check the drain path and the pan before resetting.
What is the difference between WaterFurnace fault 5 and fault 11?
Fault 5 is Freeze Detection 1 on the coax. Fault 11 is a Freeze Detection Sensor Error, meaning the freeze detection sensor is out of range. It is a separate entry in the guide from the three fault 5 causes.
How do I know if the WaterFurnace flow center is the problem?
The guide lists low or no water flow as a cause of fault 5 but does not name the flow center. Confirm the pump or flow center runs and water is moving, per your unit’s IOM.
Sources
- WaterFurnace Aurora Base Control guide, AG1562EW (faults 4, 5, 7 and 11, pp.9 and 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, standing water 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.