NO heat on bake setting. All other functions work. for the last 2 weeks the oven has taken longer to get to temp & now there is NO heat.

Check the elements for continuity with a multimeter. Sometimes the connectors draw too much current and can burn out as well. Both are easy tests. A runaway temperature can make elements fail because there is no thermostatic control, they just glow bright yellow..

it could be the oven temp sensor rod located near the top of the inside of the oven,or possibly the bake element has a hot spot on the element and can no longer pass enough current thru this spot to correctly heat to your settings a hot spot on the element will look discolored in this area

There are two possibilities for problems with the range. If it has a "timed bake" setting for the oven then it's possible that the last person who used it neglected to return the setting to the manual mode. In "timed bake" mode, the oven will heat to approx. 160 - 185 degrees, what is called a "keep warm" temp. It will maintain that heat setting regardless of what you set the oven temp control to, as long as you're not in the time frame that it's set to bake. This will make trying to bake anything a very difficult procedure.
The second possibility is that the oven glo coil igniter is cracked and will not heat to the proper temp to allow the electricity to flow through it to the oven gas safety valve to allow it to open and let the gas flow to the burner. These things are ceramic and for some reason crack in normal use. If it has a top broiler, that unit is obviously good. Unfortunately, the igniters are seldom interchangeable. You would need a tech to check the igniter with an ohmmeter.

Sorry to read about your problem, I hope this helps you out.

Bad gas control valve or oven temp control

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Usually a safety thermostat, but it can also be wiring, a control board, or a dlb relay. Call Kitchen Aid warrantee service on this, as some of the electonics have a longer warrantee on them. Good Luck, Appliance Specialists.

Turn off the power to the range. Remove the bake element from inside the oven. Be careful not to let the wires go back into the oven cavity. Take a volt/ohm meter set for ohms or continuity and test the bake element leads. If you get no reading replace the element. If you do get a reading,replace the temperature sensor in the oven.

Usually, when an oven won't heat, it's because the bake element is burned out. The bake element is the black, pencil- thick tube at the bottom of the oven. When the oven heats, the element glows red. This element has an expected life-span of several years. It may last for only one; it may last for many more. When the element burns out, you need to replace it.

good day,
hope this link below will solve your problem.

kitchen appliances

If your ignitor looks real dull orange then that is what is wrong. It needs to be bright as the sun or it is weak.

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sounds like a bad ignitor, sometimes lighting and not relighting during extended cooking time. dies it take longer than a minute to ignite gas? more then 10 in to preheat? smell gas while cookin?? all signs of a bad bake ignitor