Jandy Zodiac Aqualink Temperature Sensor for Water or Air - 7784 7785 7790 - Genuine
Jandy Zodiac Aqualink Temperature Sensor for Water or Air - 7784 7785 7790 - Genuine - is backordered and will ship as soon as it is back in stock.
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Jandy Zodiac Aqualink Temperature Sensor for Water or Air - 7784 7785 7790 - Genuine - is backordered and will ship as soon as it is back in stock.
Genuine Jandy® / Zodiac® / Aqualink RS temperature sensor for air, water, or solar temperature sensing on compatible control systems using this sensor. This is not the cheap Chinese aftermarket sensor sold on other websites. Cheap versions fail prematurely.
We keep these physically in stock for fast shipping or local pick-up, unlike most drop-shipping websites.
Commonly searched and sold under part numbers 7784, 7785, and 7790. In the official Jandy sensor family, 7790 is the common 15ft / 4.5m version.
Can be purchased with new clamp, or just sensor & o-ring.
These commonly corrode, crack, drift out of range, or fail altogether over time, causing incorrect temperature readings, no temperature reading, or erratic heater / solar operation.
Common Part Numbers / Search Terms
- 7790
- 7784
- 7785
- 7786
- 7791
- R3002900
- Jandy temperature sensor
- Zodiac temperature sensor
- Aqualink temperature sensor
- Aqualink RS sensor
- air temperature sensor
- water temperature sensor
- solar temperature sensor
- 10K thermistor sensor
Features
- 10K ohm thermistor sensor
- Approx. 15ft / 4.5m lead on the common 7790-style version
- Suitable for air, water, or solar temperature sensing on compatible systems
- Available as sensor & o-ring only, or sensor with new clamp
- Common replacement for corroded, inaccurate, open-circuit, or shorted sensors
- Cable can be extended if required by a qualified technician
Common Symptoms of Failure
- Incorrect pool or spa temperature displayed
- No temperature reading
- Temperature reading jumps around or drifts
- Solar heating not responding properly
- Heater not firing because the control system thinks the water is already at temperature
Commonly Used With
This sensor style is commonly used with Jandy / Zodiac AquaLink RS automation systems and related setups using the same 10K sensor input. It is commonly associated with:
- AquaLink RS All Button systems
- AquaLink RS OneTouch systems
- Other AquaLink RS pool / spa automation systems using 10K air, water, or solar sensors
Australian market note: Many buyers in Australia search these under Jandy, Zodiac, or Aqualink depending on the age of the system, distributor branding, and what is printed on the controller or manual.
How to Test
These are a 10K thermistor type sensor. The standard test method is to disconnect the sensor, measure resistance across the two wires with a multimeter set to ohms, and compare the reading to the actual temperature using a reliable thermometer.
- 10°C = 19.898 kΩ
- 15°C = 15.710 kΩ
- 20°C = 12.492 kΩ
- 21°C = 11.893 kΩ
- 25°C = 10.000 kΩ
- 30°C = 8.057 kΩ
- 35°C = 6.531 kΩ
- 40°C = 5.327 kΩ
If the reading is open circuit, shorted, or far outside the expected resistance for the actual temperature, the sensor is usually faulty and should be replaced.
Important Compatibility Note
Please match your existing sensor, application, and control system before ordering. While these are commonly used across AquaLink RS systems, some listings on the internet mix 7784, 7785, and 7790 together, and different systems may use different lead lengths or mounting styles. This version can be used to replace all types. Where a longer lead is required, the wires can be spliced.
In plumbing, named sizes are not the actual measurements. A pipe called “50mm” or “2"” does not measure 50 mm across. Instead, it follows nominal sizing, an internationally-standardised naming system.
Use the Outside Diameter (OD) to check your pipe against fittings. Below is a quick reference for common spa & pool pipe sizes:
| Imperial Name | Metric Name | Pipe Diameter (OD) |
|---|---|---|
| 1/2" | 15mm | ~21.2–21.5 mm |
| 3/4" | 20mm | ~26.6–26.9 mm |
| 1" | 25 mm | ~33.4–33.7 mm |
| 1.5" | 40 mm | ~48.1–48.4 mm |
| 2" | 50 mm | ~60.2–60.8 mm |
| 2.5" | 65 mm | ~75.2–75.5 mm |
These are nominal sizes and are designed to fit matching fittings — not to measure exactly what their name suggests. These are based on PVC Pressure Pipe AS/NZ 1477 Dimensions1.
- º Internal diameters vary slightly by manufacturer and class.
- 1 Not all pool/spa fittings match these dimensions exactly. Some do not follow Australian or international standards. Chinese spas may use proprietary fittings.
Understanding Plumbing Sizes & Nominal Measurements
Plumbing sizes can be confusing. PVC and many other pipe systems use nominal sizes—the size is a name, not the exact measured dimension. This convention is used across most pool and spa systems so that pipes and fittings remain compatible.
Why pipe sizes don’t match the measurements
The Nominal Pipe Size (NPS) system standardises pipe dimensions so that pipes, fittings, valves, and accessories interoperate. Plumbers work with these nominal names every day, but DIYers can be tripped up if they try to match by a tape-measure alone.
How to Measure Pipe Correctly
-
Pipe size is identified by:
- The pipe’s Outside Diameter (OD).
- The fitting’s Inside Diameter (ID) (socket opening).
- Pipe Class / Schedule (e.g., Class 9, 12, 18 or Sch 40) relates to wall thickness and therefore the Internal Diameter (ID) and pressure rating.
- The outside diameter of a fitting is not useful (wall thickness varies by manufacturer).
Hose & Tube Dimensions
Common flexible hose sizes used in pool/spa systems (approximate IDs).
| Imperial Name | Metric Name | Inside Diameter (ID) |
|---|---|---|
| 3/8" | 9–10 mm | ~9 mm |
| 3/4" | 19 mm | ~19 mm |
BSP – British Standard Pipe Thread Sizes
BSP thread names are also nominal. The thread OD will not equal the nominal name.
| BSP Thread Size Naming | Outside Diameter (mm / inch) | TPI |
|---|---|---|
| 1/16" BSP | 7.7 mm / 0.304" | 28 |
| 1/8" BSP | 9.7 mm / 0.383" | 28 |
| 1/4" BSP | 13.16 mm / 0.518" | 19 |
| 3/8" BSP | 16.66 mm / 0.656" | 19 |
| 1/2" BSP / 15 mm | 20.99 mm / 0.825" | 14 |
| 5/8" BSP | 22.99 mm / 0.902" | 14 |
| 3/4" BSP / 20 mm | 26.44 mm / 1.041" | 14 |
| 7/8" BSP | 30.20 mm / 1.189" | 14 |
| 1" BSP / 25 mm | 33.25 mm / 1.309" | 11 |
| 1-1/4" BSP | 41.91 mm / 1.650" | 11 |
| 1-1/2" BSP / 40 mm | 47.80 mm / 1.882" | 11 |
| 2" BSP / 50 mm | 59.61 mm / 2.347" | 11 |
| 2-1/4" BSP | 65.71 mm / 2.587" | 11 |
| 2-1/2" BSP | 75.18 mm / 2.960" | 11 |
| 3" BSP | 87.88 mm / 3.460" | 11 |
| 4" BSP | 113.03 mm / 4.450" | 11 |
| 5" BSP | 138.43 mm / 5.450" | 11 |
| 6" BSP | 163.83 mm / 6.450" | 11 |
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