E5 Error Code on a Thermador Range: A Troubleshooting Guide

If you’re seeing an E5 error code on a Thermador oven, it likely indicates a problem with the potentiometer or selector switch. When these components malfunction, the E5 Thermador range error code is displayed and oven operation is disabled. A failing selector or potentiometer is the most common cause of the E5 error code displayed on a Thermador oven.

In this guide, we’ll troubleshoot an E5 error display so you can identify and replace a defective oven selector and/or potentiometer.

Understanding the function of the oven temperature potentiometer and selector

Selector switch

The oven selector, also known as a range selector switch or oven function switch, allows the user to select different cooking functions or modes for the oven such as bake, broil, convection, or self-cleaning. When the user turns the selector switch to a specific cooking mode, it sends signals or activates specific electrical connections within the oven to engage the corresponding heating elements or other features required for that mode. For example, selecting the “bake” mode would activate the baking element, while selecting the “broil” mode would engage the broiler element.

The oven selector switch often includes various markings or indicators to show the available cooking functions and settings. Its exact design and functionality may vary depending on the specific oven model and manufacturer. Some ovens may incorporate more advanced selector switches with additional features, such as digital displays or programmable settings.

Potentiometer

An oven potentiometer, also known as a thermostat or temperature control potentiometer, is a variable resistor with terminals that are used in ovens and other heating appliances to regulate the temperature. It’s typically a temperature control knob or dial that allows the user to set the desired temperature for the desired cooking method.

The potentiometer is connected to the oven’s heating element or heating system and its resistance changes as the knob is turned, altering the voltage or current supplied to the heating element. Potentiometers work in conjunction with other components, such as temperature sensors and control circuits, to regulate and maintain the oven’s temperature within a range of 170°F up to about 550°F.

Causes of the E5 error display

When the oven control board detects the resistance from the potentiometer is outside of the expected calibrated ranges for the chosen temperature, an E5 error code is triggered.

Some potential causes of abnormal or out-of-range resistance from the oven temperature selector include:

• Loose or damaged wiring connections to the potentiometer.
• Broken wires or defective insulation causing intermittent contact.
• The variable resistance element itself has failed.
• A bad solder joint on the selector switch connections.

These types of issues can lead to the E5 code appearing as the control board receives improper resistance signals from the potentiometer.

Troubleshooting process

Test the selector switch

To make sure the switch is functioning properly, a continuity test can be performed using a multimeter set to the ohms range:

1. Remove power from the range before testing.
2. Rotate the selector switch to each position and note the corresponding terminals on the wiring diagram.
3. Use probe leads from the multimeter to contact the appropriate terminals in each switch position. There should be continuity (resistance reading close to 0 ohms) between the terminals.
4. Rotate the switch through each position and check for continuity in accordance with the wiring diagram. A high resistance or no reading indicates a problem with the switch contact(s) in that position.
5. If any positions do not show continuity, the switch may need to be replaced to ensure proper operation of oven modes.

Test the potentiometer wiring

When an E5 error first appears, begin troubleshooting by checking the wiring connections to the oven temperature potentiometer. Thoroughly inspecting the potentiometer wiring with these steps can help uncover and resolve connectivity issues that lead to intermittent E5 faults:

1. Turn off the power to the oven at the breaker panel or unplug the appliance. Verify the power is off before proceeding.
2. Remove the rear access panel or loosen the mounting screws to access the wiring.
3. Locate and identify the wires that connect to the potentiometer selector switch. Typically will be a pair of colored wires. Make sure these wires are firmly inserted into the correct terminals on the control board. Try removing and reinserting the connections.
4. Look closely for any damaged or burnt wire insulation that could be intermittently opening the circuit. Any compromised wires should be replaced.
5. Use a multimeter to check for continuity through each wire that connects to the selector switch. Verify that there are no open circuits.
6. Inspect the solder joints on the selector switch itself under magnification. Resolder if cold joints are found.
7. Make sure that wires are not pinched or crimped behind the oven cavity which could cause shorts.
8. Repair any wiring issues found before continuing with troubleshooting.

Check potentiometer resistance

After confirming the integrity of the wiring, the next step is to check the variable resistance of the oven temperature selector switch itself by using a multimeter. This provides a definitive confirmation of whether the oven temperature potentiometer itself has failed and is the underlying cause of E5 errors:

1. Turn off oven power at the breaker panel and unplug the unit if possible.
2. Disconnect the two wires leading to the potentiometer connections on the control board.
3. Set your multimeter to the Ohms setting, usually indicated by the Greek omega symbol.
4. Touch the multimeter probes to the two disconnected temperature selector wires.
5. Turn the oven temperature selector knob slowly from the lowest to the highest setting while observing resistance values.
6. Resistance should increase smoothly without any sudden jumps or drops.
7. Consult your oven’s service manual for the specified resistance values expected at key temperatures. For example, 1100Ω at 350°F.
8. Compare your observed ohm measurements to the specifications. Any significant variance likely indicates a defective potentiometer that requires replacement.
9. Erratic, fluctuating resistance while adjusting the selector is also a sign of failure.

Replacement process

Replace the potentiometer

If multimeter testing proves the oven temperature selector switch is defective, you’ll need to replace the failed potentiometer by following these steps.

Take care not to damage wire connections when removing and replacing the potentiometer component.

1. Turn off the power to the oven at the breaker panel or unplug the power cord.
2. Look up the exact replacement part number for the potentiometer specific to your Thermador oven model by clicking here and using our compatibility tool.
3. Remove any mounting screws or brackets to fully extract the old oven selector switch.
4. Without damaging any wire connections, carefully install the new potentiometer in the same position.
5. Attach the wire pair to the same connections on the replacement part. The colors should match.
6. Secure the new potentiometer in place using original fasteners and mounting points.
7. Restore electrical power and test oven functionality. The E5 error should no longer appear.
8. Perform temperature calibration if the oven is not heating accurately after the repair.

Replace the selector switch

The selector switch is typically located on the main control panel and is connected to various internal electrical circuits that control the heating elements, fans, and other components of the oven, depending on the selected function.

If your selector switch fails, here’s how to replace it to restore full oven functionality:

1. Turn off power to the range at the breaker panel and disconnect the power cord or wires.
2. Remove the control knobs and front panel to access the back of the control panel.
3. Note the positions of the wire leads for reconnecting later, then disconnect them from the old selector switch.
4. Unscrew and remove the retaining nut and washers to detach the old selector switch.
5. Mount the new selector switch in the same position and reinstall the retaining nut and washers.
6. Reconnect all wire leads to the new selector switch in the correct positions noted before removal. Refer to the wiring diagram if needed to avoid performance issues.
7. Remount the control panel and knobs, then restore power to the range.
8. Test the operation of the new selector switch by cycling through all oven modes.

Recalibrate the oven after installing replacements

After installing a new potentiometer and/or selector switch, recalibration may be required if the oven is no longer reaching the set baking temperature.

1. Initiate service mode by pressing and holding the Bake, Broil, and Clean buttons for 3-5 seconds.
2. The display will flash. Press the Bake button once to show the current potentiometer offset value.
3. Use the up/down arrows below Bake and Broil to adjust the offset to match the target calibration number printed on the sticker on the back of the oven or inside the oven door.
4. Press the Clean button again to exit service mode when the offset matches the sticker target number.
5. Confirm accuracy by testing the oven at varying baking temperatures.

Additional tips

For persistent or intermittent E5 errors even after replacing the oven temperature selector, here are some additional tips:

• Thoroughly re-check wire connections for any loosening over time after repair that could cause resistance spikes.
• Inspect wires for locations with damaged insulation that could be shorting against the oven chassis and impacting the selector switch signal.
• Try replacing the electronic control board which interprets the resistance signal if the selector tests have good results.
• Contact our customer service team at 1-877-477-7278 or chat with a pro at AppliancePartsPros.com.

We hope that by carefully following the step-by-step troubleshooting and replacement guidance in this article you’re able to resolve the E5 fault occurrence and restore normal oven functionality. For further troubleshooting assistance and guidance, make sure to check out our DIY Blog,  subscribe to our YouTube channel, and follow us on Facebook.