Whirlpool oven not maintaining consistent temperature

House came with an electric Whirlpool oven/range. The oven either runs too hot or too cold. A few weeks ago I started putting a meat thermometer inside the oven while it’s in use. Its the type with a long cord and the display can be placed on the counter so I don’t have to open the door. I understand ovens fluctuate, but this one is fluctuating over a 100 degrees. Tonight I tried to bake a cake. Set the oven to 325, thermometer read 320. Came back to the oven half hour later and the thermometer read 280. 15 minutes later it was still dropping and the cake wasn’t done. Increasing the temp using the controls did nothing. We are remodeling our kitchen next year, so I don’t want to buy a new oven just yet! Does this sound fixable?

Wanted to add, it can also run too hot at times. Had it set at 325 the other night and the thermometer showed it was near 390. I opened the door and it felt too hot. I know the thermometer I’ve been using is pretty accurate. Tonight I turned it to 400 and left the door open to see how the element looks. The entire thing glowed, but then would cut off briefly and after a moment start back up again. Did this almost immediately after turning oven on. Is this normal?

Hello,

What is the complete model number of the range?

Gene.