My oven takes forever to preheat

Oven/Range/Cooktop Repair
1

Brand:jenn-air
Model Number:jes8850bas
Main Symptom:preheat is very slow
What happens & when:Takes forever to preheat

Error Code (if any):none
Parts or tests already tried:none
Photos / video link:

2

On your Jenn-Air JES8850BAS, a very slow preheat is usually caused by one of a few common issues.

Most Likely Causes (in order)

  1. Weak or failed bake element (Most Likely)

    • The bake element provides most of the heat during preheat.
    • It can partially fail and still produce some heat, causing extremely long preheat times.
    • Inspect the element for blisters, cracks, or burned spots.

    Test:

    • Unplug the range.
    • Disconnect one wire from the bake element.
    • Measure resistance across the two terminals.
    • A good element is typically 15–40 ohms.
    • If the meter reads OL (open) or very high resistance, replace the bake element.

  2. Bake element not receiving 240 VAC

    • Even if the element tests good, the control board or wiring may not be supplying power.

    Live Power Warning:
    Extreme care should be taken when testing live voltage. These tests expose you to hazardous voltages that can cause serious injury or death. If you’re not comfortable working around live electricity, do not perform this test.

    Test:

    • Start a Bake cycle.
    • Measure voltage across the two bake element terminals.
    • You should read approximately 240 VAC.
    • If you only have 120 VAC or no voltage, the problem is likely the control board, relay, wiring, or a power supply issue.

  3. Oven temperature sensor out of calibration

    • A sensor reading warmer than the actual oven temperature can cause slow or incorrect preheating.

    Test:

    • Unplug the range.
    • Disconnect the sensor connector.
    • Measure resistance.
    • At room temperature (70°F/21°C), it should read about 1,080 ohms (±10%).
    • If it’s significantly outside that range, replace the sensor.

  4. Electronic control board

    • If both the bake element and sensor test good, but the board is not sending full power to the bake element, the control board is the likely culprit.

Additional Question

  • Does the broil element glow red during preheat?
    • Yes: The control is likely trying to assist with preheating, which points more toward a weak bake element or low bake output.
    • No: That may indicate a broil circuit or control issue, since this model normally uses both elements to speed up preheating.

I’d start by testing the bake element resistance, as that’s the most common cause of very slow preheating on this model. If it tests good, the next step is verifying that it’s receiving a full 240 VAC during a Bake cycle.