Montague Oven Error Code Er05: Thermostat Shorted
Er05 on the Montague V136EO-4I convection oven means the thermostat has failed to a short circuit, or a foreign object has shorted the pins. The manual says to check the connection, remove foreign objects from the circuit board compartment, and replace the thermostat if necessary.
High: a shorted thermostat reading means the oven cannot control temperature reliably.
What does Montague error code Er05 mean?
A thermostat that reads as a short circuit looks, to the control, like a sensor stuck at an extreme. The control cannot rely on a reading like that, so it reports Er05 on the oven control display. The manual explains it two ways: the thermostat has failed to a short, or a foreign object has shorted the pins. The second is unusual and worth taking seriously: debris, a dropped screw or a piece of wire in the circuit board compartment can bridge the pins and produce exactly this code with a sound thermostat. The manual's action list reflects that. It says to check the thermostat for connection and function, remove foreign objects from the circuit board compartment if present, replace the thermostat if necessary, and contact a service provider. It does not say what the oven does while Er05 shows, and it gives no resistance values, so we do not state either. For an operator, the useful part is knowing that the compartment itself is behind a panel.
Affected models and control systems
Montague Legend electric range model V136EO-4I, convection oven only. Er05 is listed under Service, Error Codes on printed p. 12.
Code numbers and their meaning can change between control generations. We match the full model and control before acting on a code.
What you may notice
- Er05 on the oven control display
- An oven that will not heat, or heats unevenly
- Er05 that appears soon after the control compartment was opened
Possible causes
Listed in Montague's documentation
- Thermostat shorted
- Foreign object shorting the pins
Other likely causes — what usually sits behind error code Er05 on this control. A technician confirms which one it is before any part is replaced.
- A loose screw, strand of wire or crumb of insulation lying across the board pins
- A thermostat lead whose insulation has worn through and touched the oven wall
- Moisture or grease reaching the sensor plug
Safe checks before calling for service
- Turn off the oven and let it cool.
- Do not open the control compartment to look for debris.
- Restart the oven and note whether Er05 returns right away.
- Tell the technician if anyone worked on the range recently, since a stray part left in the compartment is a documented cause.
How a technician diagnoses error code Er05
- Confirm Er05 and ask about recent service, cleaning or moves.
- With power isolated, open the circuit board compartment and look for foreign objects across the pins.
- Remove any debris found, then re-test the code.
- Measure the thermostat circuit against its specification to see whether it is truly shorted.
- Replace the thermostat if it tests shorted, and run a full bake cycle.
- The circuit board compartment holds line-voltage terminals that cannot be handled with power on.
- A short on a sensor circuit can come from several places, so it takes a meter to place it correctly.
- The manual points to a service provider for the replacement and final check.
How error code Er05 differs from similar codes
Er05 is the shorted-thermostat side of the pair. Er04 is open or disconnected, and Er05 is the only Er code where debris in the compartment is named as a cause.
Technical reference
- Document
- Montague Legend Electric Range, Operation Manual, Installation/Operations
- Edition
- No revision printed (file name: Final-Submission; listed on montaguecompany.com/manuals in 2026)
- Models / control
- Legend Electric Range model V136EO-4I (convection oven only)
- Section
- Service, Error Codes, printed p. 12
- Checked
- October 2026
We use the maker's document to read the code and do not reproduce it. Always confirm the complete model and control before applying these steps.
Related Montague range error codes
Can a loose screw really cause Er05?
The manual says a foreign object can short the pins, so yes. That is why it tells you to remove foreign objects from the compartment.
Is Er05 always a bad thermostat?
No. The manual lists two causes: the thermostat itself, or a foreign object across the pins.
Is it safe to keep baking?
We would not rely on the oven's temperature control while Er05 is showing, so wait for a service check.
Need help with Montague error code Er05?
A technician confirms the cause on site and gives you the price in writing before any work starts.