Hayward ProLogic Comm Error 1 and Comm Error 2
Quick Summary
- Comm Error 1: Communication between the local display and main board was lost — typically caused by a power event (brownout, outage). Usually clears with a 2-minute power cycle.
- Comm Error 2: Power is being applied incorrectly to the communication circuit, or the local display or main board has a hardware fault.
- Both errors: disconnect all terminal blocks and comm accessories first — an incorrectly wired VS pump interface or remote often causes these errors.
- ProLogic revision 4.10 added a separate heater terminal block — heaters wired to the wrong terminal position will cause display and comm errors.
- If error persists after terminal block isolation: test display harness continuity, replace local display, then replace main board as last resort.
What Comm Error 1 and Comm Error 2 Mean
The ProLogic local display communicates with the main board over an RS-485 serial bus running at 10VDC (terminal A on the PCB). Comm Error 1 appears when this communication link drops — usually after a brownout, power outage, or electrical noise event that corrupts the communication. Comm Error 2 is more specific: it indicates that power is being applied incorrectly to the communication circuit, pointing to hardware issues with the display harness, the display itself, or the main board's comm output.
Both errors share a common first step: any accessory plugged into the terminal blocks on the left side of the PCB can interfere with the comm bus and cause these errors. A VS pump module wired with incorrect polarity, an AquaConnect module with a damaged cable, or a secondary remote display with a short can all generate Comm Error 1 or 2.
Step-by-Step Troubleshooting
Owner-Level Checks
Step 5A: Power cycle the system
- Move the breaker supplying the ProLogic to the off position. Wait a full 2 minutes — this ensures the capacitors on the comm bus fully discharge.
- Restore power.
- If the Comm Error clears, the problem was a transient communication disruption from a power event. Monitor the system — if the error returns within a few days, there is an underlying hardware issue.
- If the Comm Error is still present after the power cycle, proceed to Step 5B.
Tech-Level Checks
Step 5B: Disconnect all terminal blocks and comm equipment
- Turn off the main breaker.
- Remove ALL terminal blocks from the left side of the PCB — this includes: the sensor/temperature block, any heater terminal blocks, the comm accessories (AquaConnect, VS pump interface, CSM, remote displays).
- Restore power. If the Comm Error clears: the problem resides in one of the removed terminal blocks or connected accessories.
- Isolate by reconnecting one block at a time, cycling power after each reconnection, until the error reappears. The last item reconnected before the error returns is the culprit.
Revision 4.10 Heater Terminal Note
ProLogic firmware revision 4.10 moved heaters to a separate terminal block. On older systems upgraded to this firmware, or on systems installed by a tech who referenced older documentation, heaters may be wired to the wrong terminal position. Incorrect heater terminal wiring is a known cause of Comm Error 1 and display issues — verify heater wiring matches the revision 4.10 wiring diagram before reconnecting.
Step 5C: Test the local display wiring harness
- If removing terminal blocks did not resolve the error, turn off the main breaker and disconnect the local display wiring harness at both ends.
- Using a multimeter set to continuity or resistance, test each wire in the harness — match wire colors from one end to the other. Every wire should show continuity (near-zero resistance).
- If any wire shows no continuity or infinite resistance, the harness has an open circuit — contact Hayward tech support at (908) 355-7995 for a replacement harness.
- If all wires show continuity, the harness is good — proceed to Step 5D.
Step 5D: Replace the local display
- Confirm the local display part number by looking at the model number label on the inside of the control door.
- Replace the local display with the matching model: GLX-PL-LOC-XX for ProLogic systems (substitute correct suffix: P4, PS4, PS8, or PS16 depending on model).
- Restore power after installation. If the Comm Error clears, the original display had an internal hardware fault generating bad data on the comm bus.
- If replacing the display does not resolve the Comm Error 2, replace the main board (GLX-PCB-PRO). The main board's comm output circuit has failed.
Common Causes After Adding New Equipment
Comm errors frequently appear immediately after a new piece of equipment is added to the ProLogic comm bus:
- Variable speed pump interface: Incorrect wire polarity on the RS-485 data lines will generate immediate Comm Error 1 or 2. Reverse the data wires (swap A+ and B−) and retest.
- AquaConnect remote: A damaged or incorrectly wired power lead can pull down the comm bus. Check that the AquaConnect module is receiving correct 11VDC from the accessory plug, not wired to line voltage.
- Secondary remote display: Address conflicts on multi-display systems can cause comm errors. Verify each display is set to a unique address in its own configuration.
Frequently Asked Questions
Comm Error 1 clears after a power cycle but comes back every few days. What is causing it?
Intermittent Comm Error 1 usually points to a marginal connection — a loose terminal block screw, a comm accessory connector that is partially pulled out, or a display harness connector that is not fully seated. Inspect all connections, reseat every connector, and tighten all terminal block screws. Intermittent errors can also be caused by electrical noise from a nearby motor or irrigation controller.
I disconnected all the terminal blocks and the Comm Error 2 is still there. Is it definitely the board?
Not necessarily — with all terminal blocks removed, only the display harness and display are remaining in the comm circuit. Test the harness continuity (Step 5C). If the harness is good, replace the local display (Step 5D). If Comm Error 2 persists after a new display, then yes — the main board's comm output circuit is the issue.
Can a VS pump cause a Comm Error on the ProLogic?
Absolutely. The Hayward VS pump communicates with the ProLogic over the same RS-485 comm bus. If the VS pump's data wires are reversed, if the cable is damaged, or if the pump's comm module is faulty, it will disrupt all comm traffic and can generate Comm Error 1 or 2. Disconnect the VS pump interface cable and test without it first.
What does "Comm Error 2" specifically mean that "Comm Error 1" does not?
Comm Error 2 indicates that power is being incorrectly applied to the communication circuit — meaning something is back-feeding voltage onto the comm bus. This is why it requires a more detailed hardware investigation (harness, display, board) rather than just a power cycle. An incorrectly wired accessory can also cause it by putting voltage on a data line.