Weil-McLain A136 Error — What It Means
The A136 error code is not documented in widely available Weil-McLain manufacturer materials, so its exact meaning depends on your boiler model and control type. Weil-McLain boilers display error numbers on the temperature screen when a fault condition stops normal operation. Because error codes vary across different series (Ultra, Evergreen, GV90+, CGa, PEG, ECO Tec, Aqua Balance), you need your exact model and CP/serial number to look up the precise definition in your service manual or fault-history menu.
Without model-specific documentation, do not guess at the root cause or replace parts blindly. Record the code, note your boiler series, and consult the manufacturer service literature or a qualified technician. Weil-McLain directs contractors to use the exact model/CP number and failed-part description when ordering replacement parts or initiating warranty claims, which underscores the importance of correct diagnosis before buying anything.
Before You Replace Anything
Homeowners sometimes replace the main control board or an igniter when the real fault is a wiring connector that has backed out or a sensor reading out of range. Pull the fault history from the control display and measure sensor resistance before ordering a board.
Common Causes
- Temperature or pressure sensor fault (~35%) A failed or out-of-range sensor (supply, return, or pressure transducer) can trigger an alarm that stops the boiler and displays a numeric code.
- Wiring connector loose or corroded (~25%) A connector that has backed out at the sensor, circulator, or control board interrupts the signal and the control logs a fault.
- Control-board software or memory issue (~20%) A control may store a phantom fault or require a full reset if power was interrupted or firmware experienced a glitch.
- Low system pressure or air lock (~15%) Inadequate water pressure or trapped air can cause a safety lockout and an error display, even if the pressure switch or sensor itself is working.
- Ignition or flame-sensing fault (~5%) If the code relates to combustion, a dirty flame sensor, faulty igniter, or gas-supply problem will prevent ignition and log an error.
Quick Diagnosis
Answer these to narrow it down fast.
Does your boiler's fault-history menu show A136 as a stored (past) fault, or is the code displayed right now?
No: If the code is active and the boiler is locked out, proceed to verify system pressure and check all wiring connectors before calling for service.
Is the system-pressure gauge in the green zone (typically 12-15 psi when cold)?
No: Low pressure can cause a lockout. Add water via the fill valve until the gauge reads in the green, purge air from the system, then reset and observe.
After one power-cycle reset, does the same A136 code return immediately or within a few minutes?
No: If the code does not return, monitor the boiler over the next few heating cycles. Document any recurrence pattern (time of day, outdoor temperature) to help the tech.
Step-by-Step Fix
- Record all displayed information: write down the exact error code (A136), your boiler model, serial number, and CP number from the data plate, plus the date and time the fault appeared.
- Locate your service manual: find the installation and service guide that came with the boiler or download it from Weil-McLain’s website using your model number, then look up A136 in the fault-code table.
- Check system pressure: confirm the pressure gauge reads in the green zone (typically 12-15 psi cold). If low, open the fill valve slowly to bring pressure up, then close it and purge air from the system using the vent screw on the circulator or air separator.
- Inspect all wiring connectors: with power off at the boiler switch or breaker, gently tug each connector at the control board, sensors, circulator, and limit switches to verify they are fully seated and not corroded.
- Attempt a single reset: restore power, press and hold the reset button (if your control has one) or cycle the boiler power switch off for 30 seconds and back on, then observe whether the fault clears or returns.
- Pull the fault history: if your control has a menu mode (consult the manual for button sequence), navigate to fault history to see if A136 is logged with a timestamp and whether other codes appear alongside it.
- Call a qualified technician: if the code returns, if the manual does not list A136, or if you see multiple faults, contact a Weil-McLain service professional with your model/CP number and the fault log so they can diagnose with manufacturer tools and documentation.
Parts Often Needed
| Part | Notes |
|---|---|
| Temperature or pressure sensor (model-specific) | Amazon | Supply your exact boiler model and CP number so the supplier can match the correct sensor connector and resistance spec. |
| Main control board (model-specific) | Amazon | Only replace after verifying all sensors and wiring test good. Board part numbers vary by series and control type. |
When to Call a Pro
Call a professional immediately if the A136 code appears and you cannot find it listed in your boiler’s service manual, if the fault returns after a single reset, or if you are uncomfortable working near gas piping and electrical controls. Because Weil-McLain uses different control platforms across its Ultra, Evergreen, GV90+, CGa, PEG, ECO Tec, and Aqua Balance lines, accurate diagnosis requires the correct service literature and a meter to test sensor resistance, voltage, and continuity. A qualified technician will pull the fault history from the control, measure all sensor readings against the model-specific table, and verify gas pressure, ignition sequence, and condensate drainage if applicable. Attempting repeated resets or replacing parts without a confirmed diagnosis wastes time and money and may void your warranty, since Weil-McLain requires the exact model/CP number and failed-part documentation for warranty claims.
Rough cost: A pro service call runs about $200-500.