Jandy AquaLink RS Sensor Errors: Temperature Sensor Troubleshooting

Sensor Types and Locations

Water Temperature Sensor

The water temperature sensor measures pool or spa water temperature. It installs in a 3/8" hole drilled in the pipe between the filter pump and the filter. The sensor probe inserts into the pipe and is held in place with the provided clamp. An O-ring seals the penetration. The sensor wires connect to the 10-pin terminal bar per the wiring diagram (Section 5, Figure 5 in the manual).

Freeze/Air Temperature Sensor (Required)

This sensor measures outdoor air temperature and provides the data needed for freeze protection. It must be installed outdoors where it is exposed to actual ambient temperatures, but not in direct sunlight. The sensor wires connect to the 10-pin terminal bar.

Solar Temperature Sensor (Optional)

If you have solar heating panels, the solar sensor installs adjacent to the panels. It connects to pins 7 and 8 on the 10-pin terminal bar. When a solar system is installed, S1 DIP #7 must be turned ON, which reassigns the air sensor as the solar sensor. In this case, air temperature is no longer displayed and a separate Freeze Sensor Kit (Part #6996) is required for freeze protection.

Step-by-Step Troubleshooting

Symptoms That Indicate a Sensor Problem

• Temperature display shows dashes or a clearly wrong reading (e.g., 150°F when the water is obviously cool)
• Freeze protection activates on warm days
• Heater does not call for heat even though water temperature is below the setpoint
• Air temperature reads incorrectly or does not display at all
• Solar heating does not activate when panels are hot

Tech-Level Checks

Test sensor resistance

1. Power down the system at the breaker.
2. Disconnect the sensor wires from the 10-pin terminal bar.
3. Measure resistance across the two sensor wires with a multimeter set to ohms.
4. A qualified technician can test the sensor with a multimeter and compare resistance readings to the manufacturer's specifications. At higher temperatures, resistance will be lower. At lower temperatures, resistance will be higher.
5. An open circuit (infinite resistance) means the sensor wire is broken or the thermistor has failed.
6. A near-zero reading means the sensor is shorted.

Check terminal bar connections

1. Inspect the green 10-pin terminal bar for corrosion, loose screws, or damaged wire insulation.
2. Verify each sensor is connected to the correct terminal pair per the wiring diagram. Swapped sensor wires will cause the wrong temperature to display for each function.
3. Tighten all terminal screws and clean any corrosion with contact cleaner.

Inspect the water sensor installation

1. Verify the sensor is fully inserted into the pipe and the clamp is tight.
2. Check that the O-ring is in place and not leaking. A displaced O-ring can allow water to wick up the sensor wire, corroding the connection.
3. If the sensor has been in service for many years, calcium or scale buildup on the probe can insulate it from the water and cause slow or inaccurate readings. Remove and clean the probe.

Test the freeze/air sensor placement

1. Confirm the sensor is installed outdoors in a location exposed to ambient air but shielded from direct sunlight. A sensor in direct sun will read artificially high and may not trigger freeze protection when needed.
2. A sensor mounted inside the Power Center enclosure will not read outdoor temperature accurately.

DIP Switch Interactions with Sensors

DIP Switch	OFF	ON
S1 #5	Normal operation	Factory calibration mode: temperature delays eliminated, solar temperature displayed. Do not leave ON.
S1 #7	No solar system. Air temperature is displayed normally.	Air sensor becomes solar sensor. Air temperature no longer displayed. Freeze Kit #6996 required.
S2 #1	Solar heating control enabled (if solar sensor connected).	Heat pump control enabled. Solar heating control disabled.

Common Parts That Fix This Problem

• Jandy temperature sensor (replacement thermistor with cable and clamp)
• Sensor O-ring (for water temperature sensor pipe penetration)
• Adjustable Freeze Sensor Kit, Part #6996 (required when S1 DIP #7 is ON for solar installations)
• Green 10-pin terminal bar (if terminals are corroded beyond cleaning)