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Bosch HBL8750UC/11 - Oven keeps resetting time display. Oven and microwave both work.

emhunt44

Member
Joined
Nov 23, 2020
Messages
1
Location
US
Model Number
HBL8750UC/11
Brand
Bosch
Age
6-10 years
Bosch HBL8750UC/11 - Oven keeps resetting time display. Oven and microwave both work. Replaced the oven control module and still happened. Is this an appliance issue or power surge/electrical issue?
 

rickgburton

Appliance Tech - Moderator
Staff member
Joined
Jul 11, 2006
Messages
41,528
Location
Murray, Utah 84107, United States
Unfortunately the part you need is no longer available:
bosch-display-module-703850-ap5264471_01_m.jpg
 

guho

Premium Member
Joined
Apr 13, 2021
Messages
2
Location
NY
@emhunt44 My oven is almost the same type: HBL8450UC/10 and does the same thing. I also replaced the control module (with the relays, didn't help) and am afraid I will have to find a replacement display module. But did it actually help? It could also be the 9.6V DC power supply module going bad of course. Thanks for posting back.
 

rickgburton

Appliance Tech - Moderator
Staff member
Joined
Jul 11, 2006
Messages
41,528
Location
Murray, Utah 84107, United States

guho

Premium Member
Joined
Apr 13, 2021
Messages
2
Location
NY
@rickgburton thank you for responding.

This part is actually still available and in stock, even from Bosch directly.

Edit: this is the direct part link: bosch-home.com/us/shop-productlist/00703850

The cost is prohibitive at $495, but I would still consider it if I could find a testimonial that it actually helped. Last month when I opened the oven, the voltage checked out at 9.6VDC. But using my multimeter, I can't see if perhaps the DC voltage has ripples or other problems. Is failure of the DC power in electric wall ovens a common failure mode? Or is it more common that the front panel board develops a fault? I reseated all connectors to rule out bad connections. I even tried a new main control board (with the relays) but that did not help. The cost was low and one of my relays was stuck (broil element). So that is now fixed. But I still randomly lose time & date on this wall oven every few days while no other appliance or device in the house had a power outage.
20210331_173224.jpg
 
Last edited:

rickgburton

Appliance Tech - Moderator
Staff member
Joined
Jul 11, 2006
Messages
41,528
Location
Murray, Utah 84107, United States
Is failure of the DC power in electric wall ovens a common failure mode?
Most ranges and wall ovens don't use a dedicated DC power supply. Most control boards use a bridge rectifier to convert AC to DC and some have a transformer on the board. I never deal with Bosch directly but if they say they have one I won't argue. All my parts sites show it as no longer available.
perhaps the DC voltage has ripples or other problems.
I've never heard of such a thing. Check the input voltage and signal voltage from the UI. Input voltage across pin 1 to pin 3 is 9.6 VDC. Pin 1 to pin 2 is signal voltage and will fluctuate between 5V and 4.7V every two seconds. If the voltage is constant, there is a problem with the signal from the UI.
 
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