Hayward HeatPro Pc/SH Error: Shorted Water Temperature Sensor
Quick Summary
- Pc (HeatPro) and SH (Summit) indicate the water temperature sensor circuit is shorted — resistance is near zero or much lower than expected for the current water temperature.
- HeatPro uses a 10k ohm sensor; Summit uses a 4.8k ohm sensor. Use the correct resistance chart for the model you're working on.
- Check for shorted or pinched wires between the sensor and the control board before replacing the sensor itself.
- If sensor resistance is correct but Pc/SH persists, replace the control board.
What Pc/SH Means
Pc on HeatPro (or SH on Summit units) means the water temperature sensor circuit is reading abnormally low resistance — indicating a short circuit. With a thermistor-type sensor, resistance decreases as temperature increases, but a shorted circuit reads near zero ohms regardless of temperature. The control board interprets this as an impossibly high water temperature and shuts down to prevent overheating.
The diagnostic approach for Pc/SH is the mirror image of PO/OP: instead of looking for an open (infinite resistance), you're looking for a short (near-zero resistance). Always measure resistance at the sensor before condemning any component.
Step-by-Step Troubleshooting
Step 1: Inspect the Sensor Wiring for Shorts
A shorted sensor circuit most often means two wires that should be separate are touching. This can happen due to:
- Pinched wiring in a conduit entry point or a panel edge
- Wire insulation damaged by rodents or sharp edges, allowing bare conductors to contact each other or a grounded surface
- Moisture intrusion at a connector causing current to bridge across pins
- A connector that was pinched during panel reassembly
Trace the sensor wiring from the sensor to the control board, inspecting carefully for any of these conditions. Pay particular attention to where wiring passes through panel openings or conduit fittings.
Step 2: Measure Sensor Resistance
- Disconnect the sensor wiring at the control board connector.
- Set your VOM to the 20k ohm range.
- Measure resistance wire-to-wire at the sensor end of the harness.
- A reading of 0 or very near zero ohms confirms a shorted circuit. Compare against the 10k ohm sensor chart for the actual water temperature to quantify how far off the reading is.
- For a pool at 75°F, the HeatPro sensor should read approximately 10.5k ohms. A reading of 0.5k ohms or less at any realistic pool temperature indicates a failed sensor or shorted wire.
Step 3: Isolate Sensor from Wiring
To determine whether the short is in the sensor itself or in the wiring harness:
- Disconnect the wiring at the sensor end (where the sensor connects to the harness).
- Measure resistance directly at the sensor terminals, not through the wiring.
- If the sensor itself reads near zero, replace the sensor.
- If the sensor reads correctly but the harness reads near zero, the short is in the wiring — replace or reroute the damaged section of wire.
Step 4: Replace the Sensor or Wiring
If the short is in the sensor:
- Turn off the heat pump and pool pump. Close isolation valves if available.
- Unscrew the sensor from its fitting in the water manifold.
- Wrap threads of the new sensor with PTFE tape and install snugly.
- Reconnect wiring and test operation.
Step 5: Replace the Control Board
If sensor resistance tests correctly against the chart (approximately 10k ohm range at typical pool temperatures) but Pc/SH persists after reconnecting, the control board is misinterpreting the sensor signal. Replace the interface board. Always confirm the replacement board part number against the unit's model and serial number.
Frequently Asked Questions
Can moisture inside the heat pump cause a Pc/SH error?
Yes. Moisture at the sensor connector or inside the harness can create a conductive bridge across the circuit, effectively shorting the sensor signal. If the unit has been exposed to flooding, heavy condensation, or pest intrusion, inspect all low-voltage connectors for moisture. Dry out and clean the connectors before re-testing.
What is the difference between Pc/SH on the water sensor versus dPc/cSH on the defrost sensor?
Both codes indicate a shorted sensor circuit. Pc/SH refers to the water temperature sensor that monitors pool water temperature. dPc/cSH refers to the defrost temperature sensor clamped to the suction refrigerant line near the TXV bulb. The diagnostic procedure is the same, but you're testing different physical sensors in different locations. Confirm which error code is displayed before testing.
Why would a sensor fail shorted rather than open?
Thermistors can fail in either direction. A shorted failure usually means the internal resistance element has been physically damaged — often from overheating, freezing, or water damage that causes the element to crack and bridge. An open failure is more often a broken wire or a thermistor element that has simply degraded over time.
Is Pc/SH more likely to cause the heat pump to run non-stop or shut down?
Pc/SH causes the heat pump to shut down as a safety measure. With an apparent shorted sensor, the board reads an impossibly high water temperature and stops heating. This prevents the unit from continuously heating what it believes is an already overheated pool. The opposite failure (PO/OP) also causes shutdown — both open and shorted sensor conditions result in a fault stop.
The sensor tested fine on my last visit but now shows Pc/SH. Can sensors fail intermittently?
Yes, intermittent sensor shorts can occur when a sensor or connector is borderline and only shorts under certain conditions — such as when the harness flexes in wind or when the connector heats up and expands. If a sensor tests good when cold but faults when the unit warms up, the fault is often at a connector where heat causes expansion that bridges the pins. Inspect and re-pin connectors before replacing the sensor.