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HBL8451UC Bosch Oven - Control Board Replacement

Jross4

Premium Member
Joined
Nov 13, 2021
Messages
5
Location
New York
Model Number
HBL8451UC
Brand
Bosch
Age
6-10 years
I have an older Bosch 800 series single wall oven that has been malfunctioning. The oven greatly overshoots the set temperature no matter the mode it is set. I had a repair service come look at it and they felt it could either be the temperature sensor, bake element, or control board, however, they quoted me $1,000 for these repairs. While I am not the most handy guy, I figured that I could make these repairs for a lot cheaper. I replaced the temperature sensor and still had the issue. I then replaced the Bake element and continued to have the issue. I then “attempted” to replace the control board, but clearly I did something incorrectly because the circuit shorted once I turned it back on at the breaker. Does anyone have instructions or a video that could help install the board correctly?

Appreciate any help as I’d love to avoid overpaying to have this repaired. Thanks in advance!
 

rickgburton

Appliance Tech - Moderator
Staff member
Joined
Jul 11, 2006
Messages
44,797
Location
Murray, Utah 84107, United States
I’d love to avoid overpaying
You're not off to a good start.
The oven greatly overshoots the set temperature
Most ovens will overshoot the set temperature on the first rise and even the second rise. I'll assume the temperature gets too hot and stays there, correct?
I had a repair service come look at it and they felt it could either be the temperature sensor, bake element, or control board, ....... they quoted me $1,000 for these repairs.
Bake element wouldn't cause this problem and if the oven sensor measured 1100Ω you don't need to replace it. (Did you have to pay this repair company for that ?) I get the feeling he had no idea what the problem was so he quoted you such an outrageous amount knowing you would say no. The part cost $225 so $775 for labor?? I don't think so!
I then “attempted” to replace the control board,
What is the part number of the control board you replaced? Where did you get it?
I did something incorrectly because the circuit shorted once I turned it back on at the breaker.
That short may have damaged your new board. Here's a few guidelines for replacing control boards. First and foremost, remove power from the machine. Most manufactures design the boards so no two connectors are the same but some are. Take a picture of the connectors on the board before you start. When you replace the board, remove it but leave all the connectors connected then install the new board. Replace the connectors, one at a time, from the old board to the new board. Do not force anything Check your work before you restore power.
Does anyone have instructions or a video
You might check youtube. The board is pretty much plug and play. The board sits on six posts. Press in on the release tab and pull the board up and off.
PC BOARD.jpg
 

Jross4

Premium Member
Joined
Nov 13, 2021
Messages
5
Location
New York
Thanks for the detailed reply. The oven was heating up far beyond the temperature to which it was set and was staying there resulting in everything I cooked being burnt.

I did not have the repair service do any of the repairs because, as you said, the cost of labor seemed extremely high. I think I may have figured out where I screwed up with the control board. Embarassingly, I did not install the board using the posts beneath it-so I am assuming that the board shorted out from contacting the metal surface below the board. I cannot find the plastic posts/standoffs though. Any idea where I may be able to purchase replacements?
 

rickgburton

Appliance Tech - Moderator
Staff member
Joined
Jul 11, 2006
Messages
44,797
Location
Murray, Utah 84107, United States
If that's the case, I'm pretty sure the board is history. Did you check the old board for the plastic posts? They're not always plastic. How did you get the old one off?
 

Jross4

Premium Member
Joined
Nov 13, 2021
Messages
5
Location
New York
Not quite sure what happen to the post/standoffs from the original. I purchased nylon spacers and installed a new board and it powered up without shorting so I’m quite sure that was the problem. Testing the temperature settings with the new board by baking a pot pie. If it does not overcook, I am going to consider the oven repaired. For long term though, I do want to use the appropriate spacers as I’m sure the heat could cause these to melt. Anyone have a suggestion on which spacers I should purchase?
 

Jross4

Premium Member
Joined
Nov 13, 2021
Messages
5
Location
New York
Did you check the old part or look around inside the top for them?
Yes, I looked around. Cannot find them. They were probably moved or discarded by my wife... Any suggestions on replacements?

So far, the oven has not overshot temperature or burned anything. However, it is unable to preheat to 400*F while on Bake when set to 400*F (it stops at 350*F and continues to preheat, but never makes it there). It is able to reach 400*F Convection Bake and Roast though. Thoughts on this? Bad bake element?
 

rickgburton

Appliance Tech - Moderator
Staff member
Joined
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Messages
44,797
Location
Murray, Utah 84107, United States

Jross4

Premium Member
Joined
Nov 13, 2021
Messages
5
Location
New York
Checked continuity on all 3 heating elements and they all check out. Visually the Bake element appears intact without any significant corrosion. Since Bake is the only cooking mode which is struggling to reach its preheat temperature, is it safe to assume that the Bake element might still be bad?
 

rickgburton

Appliance Tech - Moderator
Staff member
Joined
Jul 11, 2006
Messages
44,797
Location
Murray, Utah 84107, United States
Bake element wouldn't cause this problem
The elements are like lightbulbs. They're either god or bad. Bosch doesn't make it easy to find any service information. Check the oven sensor for 1100Ω at room temperature. Is that a new board that's in there now? I found the spacers or at least the part number as they are out of stock:
 
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