This error is shown when the Bed does not reach the required temperature as set by the machine. To confirm that the error is related to bed, you can check the last word of the error, which says “Bed”.
Schematics of Heater wiring.
This error comes when the bed does not get heated to the required temperature according to the temperature set by the printer. The printer has an inbuilt program that monitors both the temperature and the power supply to the heating elements. So when a certain temperature is set, the printer starts supplying power to the bed heater and takes the temperature reading using the thermistor. If the temperature does not increase after a certain period of power supply to the bed heater, the printer detects an issue and stops.
Troubleshooting:
This error can be caused by 3 issues.
1. Faulty Thermistor.
2. Faulty SSR.
3. Faulty Bed Heater
4. Wiring: Loose connection.
1. Faulty Thermistor:
Min Temp error for bed-
1. Take a multimeter and check the resistance of the Thermistor. If the thermistor is giving incorrect readings, then the thermistor is damaged and needs replacement.
Remove the thermistor wire
Check the resistance on the Resistor. The resistance should be around 90 Ohms
otherwise.
If the thermistor is giving correct readings, then the wiring is faulty. You need to check the wiring of the Thermistor till MKS. There will be some connectivity issues that will hinder the transfer of thermistor data to MKS. Fixing the connection will solve the issue.
2. Faulty SSR/SSR wiring.
1. Check the power supply to the SSR:
SSR is the component that supplies power to the heater bed for heating. If the wiring from the power switch to the SSR is damaged the the SSR and Heater bed will not get a power supply.
How to check?
Take a multimeter and check the current at the SSR input (for neutral probe, use the neutral wire in the Power switch of the SMPS). If the input is not there, then check for loose connections near the power switch. If the input is correct, then check the output terminal of the SSR.
Use a neutral pin in the SMPS and the line input in the SSR
Close up
In case the supply is correct, the Voltage should be around 220V
Note: The line input and line output can be interchanged, as there is no polarity. SSR just creates continuity, which starts the current supply to Bed
Checking the working of SSR:
If the Bed heating is turned on, then the SSR output should be 240 Volts. If the bed heating is not on, then the SSR should not be supplying any current
In case of a faulty SSR, the SSR will supply or not supply current irrespective of the bed heating state.
If the SSR is not switching between on and off with respect to bed heating status, the SSR is spoiled.
Check the other pin, use the SMPS neutral for the probe.
For confirmation, check the MKS output terminals.
When the bed is in heating state, the MKS bed heater terminal should output 24 volts. When the Bed is not heating, the output should be zero.
Note: There are chances of MKS not giving commands to SSR for switching. So, before confirming that SSR is damaged, do a confirmation test by checking the MKS output.
Start bed heating and check the voltage. It should be 24V or 12V
If the MKS is outputting 24V or 0V irrespective of ON OFF status, then the MKS is damaged and the SSR is not functioning since the MKS is not giving it input. MKS needs to be replaced if MKS is faulty. If MKS is fine and SSR is not functioning properly, then SSR needs to be replaced.
If both SSR and MKS are working fine, then the Bed heater will be faulty.
To check if the Bed heater is faulty, you should check the resistance of the bed heater. Take a multimeter and connect it to the terminals of the Bed heater. The resistance should be around 100 ohms. If the bed heater is faulty, the resistance will not be shown correctly.
Remove the wire connected to the bed heater.
Remove the neutral wire from the SMPS to get the correct resistance.
Check the resistance of the heater Bed using the line and neutral points. The resistance should be around 140 ohms.
To confirm that it is bed heater damage and not a wiring issue, cut and remove the solder of the bed heater wire and check. If the resistance is shown correctly when you connect directly, then the wiring was faulty. So replace the wires and solder new wires. Or else the bed heater needs to be replaced.
