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HBL8450 Bosch Oven Heating Woes -- Normal?


Premium Member
Feb 16, 2021
Model Number
1-5 years
We are pretty frustrated because we bought a new HBL8450 oven and a new microwave (several thousand dollars worth) only 18 months ago and we’ve had numerous issues. We could really use some advice right now to determine if this behavior below is normal. Perhaps if someone can explain what’s expected...or needed for repair.

We’ve confirmed the following with TWO brands of oven thermometers, but we started down this path many months ago when we noticed our cakes weren’t baking correctly and most recipes (even frozen food) was taking more time than typical. For cakes, consistent/proper temperature is especially important.

The oven seems to preheat properly: what we enter as a set point is reached in about 15m-20m and looks accurate. If we do an offset that is accurately reflected as well. The oven seems to understand the preheating temperature. This is where things don’t seem right:
  • Temperature drops drastically when food goes in, as expected.
  • However far the temperature dips—25, 30 degrees—it stays put.
  • Around 12 minutes in we notice the temperature starts climbing, finally reaching the set point again around 15m in
  • We notice after another 10m or so the temperature starts climbing well beyond the set point.
  • This is an issue because most food and cakes bake 20-30m, meaning most of the time has been under temperature (15m under and about 10m at set point).
  • We have attempted to compensate with a 12 degree offset, but that really over-temps that last 10-15m of bake time.
In our mind the oven should immediately see the drop in temperature and begin to take action quickly. Sometimes we can even see the temperature continue to drop slightly after it has stabilized from opening the door. At a 350 degree set point, the oven will spend 10-12 minutes at 325 or lower. It’s as if the oven doesn’t understand that it’s too low. It just doesn’t cut it.

Any information on if this is expected and/or how it should work is greatly appreciated.
Model Number HBL8450_ _ _

That model number is incomplete. Did you get it right off the appliance's model and serial number identification tag? That's the only place the complete information will be found. You can find tips for locating the model and serial number identification tag on your appliances at the following link:

LINK > Model Number Tag Location Guide

bovino said:
Any information on if this is expected and/or how it should work is greatly appreciated.

I'm afraid i have no experience with Bosch ovens but another forum member posted a link to a service manual. Maybe it covers your model to describe its programmed operation?

LINK > Forum Message: HBL8650UC/10 Bosch double oven...

Dan O.
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