Confirming a Bad Relay

Overview

The bed heater relay functions as an electrically controlled switch that regulates power to the heater pad mounted on the underside of the heated bed. The relay turns the heater on and off in response to commands from the printer’s control board, allowing the bed temperature to be maintained at the requested setpoint.

If the heated bed fails to heat when commanded, or if the printer displays the error “Heater bed is not heating at expected rate”, the issue is commonly caused by either a loose relay connection or a failing bed heater relay. 

Before ordering a replacement relay, there are several checks you can perform to determine whether the issue is a wiring/connection problem or an actual relay failure.

Parts and Tools Needed:

• Multimeter
• Phillips Head Screwdriver
• A replacement relay 

NOTE: If you are a Gigabot owner and you have a model that is GB3 and beyond, then you most likely have an Archimajor board with Klipper firmware integration. Earlier models (GB2 and earlier) will have an Azteeg board with Marlin firmware integration.

Steps for Confirming Relay Integrity:

• In Part A - Checking for Faulty Relay Connections, we will measure the continuity of the connections on our bed heater relay output terminals while the bed is heating.
• In Part B - Checking for a Faulty Control Board Connection, we will verify that the signal sent from the printer's control board is present and correct to the relay's input side.

Part A - Checking for Faulty Relay Connections:

          Azteeg Board                                                                                                        Archimajor Board

1. Turn the printer off and unplug from the outlet. Open the electrical box and locate the bed heater relay (circled in BLUE) and the two screw terminals for the control board connection (circled in YELLOW). 
2. Lightly tug on the wires connected to the screw terminals and ensure they are firmly secured. If they are not firmly secured, loosen both screws and re-tighten with the Phillips head screwdriver, ensuring the connection for both terminals is firmly intact.
3. After ensuring they are secure, turn on the printer and preheat the bed to 60°C. While the bed is preheating, ensure that the green relay LED light turns on. Then, apply both probes of the multimeter to each terminal. Confirm there is a 24V DC continuity between both points.

Note: The Crydom bed heater relay is a solid-state relay (SSR). This means that if the relay is not energized (not activated), there will be no continuity between the two terminals (input/output) on the relay. The circuit will remain open, and the multimeter will show there is not any continuity between both points. For that reason, it is important to fully preheat the bed before checking continuity with the multimeter. 

(If the heater bed error persists and/or there is no continuity between both terminals, then proceed to Azteeg Board: Part B - Checking for a Faulty Control Board Connection)

Part B - Checking for a Faulty Control Board Connection:

          Azteeg Board                                                                                                         Archimajor Board

1. Locate the two bed heater control terminals (circled in RED).
2. While the bed is still fully heated to 60°C, apply each probe of the multimeter to both terminals. Confirm there is 24V DC between the terminals.

Note: Make sure that the metal probe of the multimeter is in contact with the metal terminal on the board itself. That is the only way to measure whether you have successful continuity. 

If you find there is successful continuity of 24V DC between both locations but the small green LED light on the relay is not on while preheating the bed, then the relay will need to be replaced.

If you find there is no sign of continuity at either location, then the next step is to test  whether the controller is faulty or if the wire between the controller and the relay is faulty. Please email [e-mail] , and our support team will be happy to assist you and help troubleshoot the next steps.

Helpful links:     Azteeg wiring diagram             Archimajor Wiring Diagram

Questions or concerns? Reach out to our support team at [e-mail] to open a support ticket.