Oven Won't Heat - Diagnostic Tree

Symptom

Customer reports an oven that won't heat. Different from "won't turn on at all" - the oven powers up, displays are normal, customer sets temperature + nothing happens. Different from "won't ignite" (gas range cooktop). Standard service call; diagnosis is typically electrical-component testing.

Likely Causes (Electric Ovens)

In order of frequency:

• Failed bake element (lower heating element) - 30 %
• Failed broil element (upper, in dual-element ovens) - 15 %
• Failed igniter (gas oven; weak spark) - 15 %
• Failed gas valve (gas oven; won't open) - 10 %
• Failed control board - 10 %
• Failed temperature sensor - 8 %
• Failed safety thermostat (high-limit cutout) - 5 %
• Failed door switch - 4 %
• Failed thermal fuse - 3 %

Diagnostic Steps

For electric ovens:

1. Visual inspection. Pull oven racks; inspect the bake element + broil element:

• Blistered, broken, or discolored: confirmed failure; replace
• Visually intact: continue testing

1. Test bake element with multimeter:

• Cut power; unplug oven
• Remove screws holding bake element + pull it forward enough to access terminals
• Test continuity end-to-end: ~20 - 50 ohms typical for residential
• Open circuit → bad element; replace

1. Test broil element similarly.
2. Test temperature sensor:

• Sensor is the small probe in the back of the oven cavity
• Test resistance per manufacturer spec
• Open circuit at room temp → sensor failed

1. Test safety thermostat (high-limit cutout):

• Located behind the rear panel
• Resets typically; if continuously open, replace

1. Test control board (last resort - expensive to replace):

• Verify voltage at the element output during bake call
• If board commands voltage but elements don't heat, element is bad
• If board doesn't command voltage, board is bad

For gas ovens:

1. Test the igniter. Bake call should produce a glowing igniter within 30 - 60 seconds:

• If igniter doesn't glow OR glows weakly, replace
• "Weak" igniter glows orange but not bright enough to open the safety valve = won't heat

1. Test the gas valve:

• Verify gas supply is on
• Listen for gas-flow click when igniter glows
• If igniter glows correctly but no flame, gas valve solenoid bad

Resolution

• Failed element: replace.
• Failed igniter (gas): replace. NEVER touch the igniter with bare hands; oil from skin causes hotspots that shorten lifespan. Use clean cloth or gloves.
• Failed gas valve: replace. Verify gas line pressure to valve.
• Failed temperature sensor: replace.
• Failed safety thermostat: replace; investigate why it tripped (chronic overheat = related issue).
• Failed control board: replace. Often makes more sense to replace oven if older.

Verification

• Oven heats to set temperature within manufacturer's spec time (typically 10 - 15 min to 350°F)
• Holds temperature without overshooting
• Customer demonstrates baking a known item

References

• Manufacturer service literature for the specific oven
• Manuall internal: Gas Range Burner Won't Ignite - Diagnostic Tree, Refrigerator Not Cooling - Diagnostic Tree