A slow or incomplete preheat on a built-in wall oven is one of the most common calls we get, and the good news is that the two most likely causes are both routine repairs.
The Bake Element
A visibly glowing but weak bake element, or one that shows scorching or a visible break, is losing efficiency even if it technically still turns on. This is the most straightforward of the two causes to confirm and replace.
The Temperature Sensor (Probe)
A drifting oven temperature sensor tells the control board the oven is hotter than it actually is, so the board cuts heat early — this reads exactly like a slow-preheat complaint even though the element itself is fine.
Ruling Out the Simple Stuff First
Before assuming a part has failed, confirm the door is sealing fully closed and that nothing is blocking the vent — both can mimic a heating fault on a wall oven built into tight cabinetry.
What This Costs to Fix
Both a bake-element and a sensor replacement are inexpensive relative to the size of the unit, and either is typically a single-visit repair on our Monogram wall oven repair calls.