How to Fix a Commercial Oven That Won't Heat Properly
Jan 16th 2026
In a commercial kitchen, the oven is the workhorse. When a fryer goes down, the line cook can sometimes improvise. But when the convection oven stops heating correctly, the entire menu grinds to a halt.
For a service technician, an "oven not heating" call is standard fare, but the root cause can range from a $15 thermocouple to a complex control board failure. Your goal is simple: diagnose it accurately, find the part, and fix it.
This guide breaks down the troubleshooting workflow for both gas and electric commercial ovens to help you achieve that first-time fix.
The "Universal" Checks
Before diving into the gas train or the heating elements, check the components that affect every unit, regardless of fuel type.
1. The High-Limit Switch
If the oven has absolutely no heat but the power is on, start here. The high-limit switch is a safety device designed to trip if the oven exceeds a safe temperature (usually due to a stuck thermostat or fan failure).
- The Check: Locate the high-limit reset button (usually on the back or behind the control panel). If it has popped, reset it.
- The Catch: Switches don't trip for no reason. If you reset it and it trips again, you likely have a thermostat that is stuck "closed" (calling for heat continuously) or a convection fan that isn't moving air, causing a hotspot.
2. The Door Switch
On convection ovens, the fan and heating system often won't engage if the door switch reads "open."
- The Check: Listen for the fan shutting off when you open the door. If the fan never turns on even when the door is closed, the plunger switch might be broken or misaligned.
Troubleshooting Gas Ovens
If the unit is gas, your problem is usually ignition, sensing, or flow.
1. The Pilot and Thermocouple
If the pilot won't stay lit, the main burner will never get the signal to open.
- The Symptom: You light the pilot and hold the knob, but the flame dies the second you let go.
- The Fix: This is classic thermocouple failure. The thermocouple generates a millivolt signal to keep the safety valve open. If the tip is dirty or burned out, the voltage drops, and the valve shuts.
- Pro Tip: Check the connection at the valve before replacing. Sometimes it’s just loose. If you need a replacement, Mavrik™ universal thermocouples are a truck-stock essential that fit most major brands.
2. The Igniter / Spark Module
If the unit uses a spark ignition (rather than a standing pilot) and you hear click-click-click but see no spark:
- The Check: Inspect the ceramic insulation on the igniter probe. If it’s cracked, the spark will arc to the chassis instead of the pilot hood. Also, check the high-voltage cable for continuity.
3. The Gas Valve
If the pilot is on, the thermostat is calling for heat, but the main burner won’t fire, check the valve.
- The Check: Use your multimeter. Is the valve receiving 24V (or 120V, depending on the system)?
- Yes: If it has voltage but isn't opening, the solenoid is bad. Replace the valve.
- No: If it has no voltage, the issue is upstream, likely the thermostat or a safety switch.
Troubleshooting Electric Ovens
Electric ovens are simpler mechanically but carry higher voltage risks. Always Lockout/Tagout (LOTO) before touching terminals.
1. The Heating Elements
If the oven is heating slowly or only reaching half-temp, you likely have a dropped leg or a blown element.
- Visual Check: Look for blistering, cracks, or breaks in the element coils.
- Meter Check: Disconnect the wires and measure resistance (Ohms) across the element terminals.
- Reading: If you get a reading (e.g., 10-50 Ohms depending on wattage), the element is good.
- Infinite (OL): The element is severed inside. It needs to be replaced.
2. The Contactor
The thermostat tells the contactor to close, sending high voltage to the elements. Contactors take a beating and are a common failure point.
- The Check: With the oven calling for heat, check voltage across the coil. If the coil has voltage but the contacts aren't pulling in, the coil is bad. If the contacts are pulled in but voltage isn't passing through to the element side, the contact points are pitted or carboned up.
Temperature Control Issues
If the oven heats but the temperature is wildly inaccurate (burning cookies or undercooking chicken), it’s a calibration or thermostat issue.
- Mechanical Thermostats: These rely on a fluid-filled bulb. If the bulb is pinched or the capillary tube is kinked, the calibration is ruined. You can try to adjust the set screw inside the knob stem (usually 1/4 turn represents 25°F), but if it's off by more than 50°F, replace it.
- Temperature Probes (Digital): If the display reads an error code or an impossible temperature (like 999°F), the temperature probe (RTD or Thermistor) is likely open or shorted. Measure the resistance against the manufacturer’s chart to verify.
The "First-Time Fix" Strategy
Diagnosing the oven is the hard part. Getting the parts is easy.
- Identify the Part: Whether it's a specific Vulcan gas valve or a Blodgett motor, locate the OEM part number.
- Check for Mavrik™ OCM Options: For universal components like igniters, thermocouples, heating elements, and contactors, check if a Mavrik™ OCM equivalent is available.
- Why? Mavrik parts are sourced from the same component manufacturers as the OEM but are priced for better margins and stocked deeply to prevent backorders.
- Order by 5 PM: Order via the AllPoints app or website by 5 PM EST for same-day shipping.
Don't let a cold oven freeze your customer's operations.
Shop the industry's largest selection of parts, including 250,000 OEM and OCM essentials, at AllPointsFPS.com.
