• ** REMEMBER! **The microwave can still shock you even unplugged!!

    ALWAYS discharge the high-voltage capacitor first if you even think your hands will come close to any HIGH VOLTAGE components.

    Jeff mentions this: Anything in the high voltage ( magnetron, capacitor, diode, wires to and from ):
    ...Use a metal ( not the shiny chrome type ) screw driver with a insulated handle to short across ( touch both at the same time ) the terminals of the high voltage capacitor to discharge it.

    From Jeff's site: http://www.applianceaid.com/component-testing.php

    Jake
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FIXED Bosch Microwave HMC80252UC/01 blowing fuse

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Prak

Premium Member
Joined
Dec 4, 2015
Messages
26
Location
British Columbia
Model Number
HMC80252UC/01
Brand
Bosch
Age
1-5 years
Hey, have a bosch HMC80252UC/01 microwave, and as soon as you turn the breaker on it blows the 20amp fuse in the unit on the small filter board. It had a bad interlock switch on the right hand side, so I took that out and while I waited for the part to arrives I could turn the breaker on and it wouldn't blow the fuse. As soon as I put the new interlock switch in and turned the breaker back on, fuse blew. I tried to trace every piece of wire and connection to see what was possibly grounding out or causing that to fail and I couldn't find it. It doesn't look like these units have a HV board on them, so would it be the main control board being faulty? The HV transformer seems to not be shorted out when I tested it to ground. Any ideas? Would love some help and thanks in advance. Does anyone also have a wire diagram for this unit? Lost the wire diagram. :(
 

rickgburton

Appliance Tech - Moderator
Staff member
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Jul 11, 2006
Messages
41,351
Location
Murray, Utah 84107, United States
Check the microswitches by opening and closing the door. You may have a faulty switch holder. Since it blows right away, it's not any of the HV components.
bosch-support-00648812-ap5804844_01_m.jpg
 

Prak

Premium Member
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Dec 4, 2015
Messages
26
Location
British Columbia
I had the bad micro switch disconnected and I could turn the breaker back on and it didn’t blow the fuse. So it’s something after the switch in the circuit.
 

rickgburton

Appliance Tech - Moderator
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What do you think comes after the switch? I'll tell you, it's another switch. Sounds like you know more than me. So good luck!
 

Prak

Premium Member
Joined
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Messages
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Location
British Columbia
The first thing I tested was both interlock switches and that’s how I found the bad one on the right. Left side was fine. Any other suggestions?
 

danielsmithsd

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Nov 8, 2020
Messages
1
Location
CA
The first thing I tested was both interlock switches and that’s how I found the bad one on the right. Left side was fine. Any other suggestions?
Howdy Prak,

Any luck here? I've got the same issue, mine was the left switch--it had actually fused the contacts together. I tested the other and it seems okay, but will probably replace it anyway. I've also replaced the control board (display had gotten too dim to read). Quite the process for sure... That didn't help either.

After 6 months of being stumped, I started to tear into everything and noticed the convection element had some char on one of the wire ends. Not likely the issue since the fuse goes immediately.

Would love to hear if you had any success.
 

Prak

Premium Member
Joined
Dec 4, 2015
Messages
26
Location
British Columbia
Haven't had time to have another peak at it. Hoping to have time this week to take it apart and check out other pieces. I will let you know what I find. If you find anything please let me know as well.
 

Prak

Premium Member
Joined
Dec 4, 2015
Messages
26
Location
British Columbia
Hey, ended up changing all the door interlock switches (2 on the left as well as the 1 on the right), and it fixed the issue. The ones on the left didn't test bad when I had pulled them out initially, but when I checked them again I found they weren't as sensitive so the white lever wasn't activating the one switch. Hope that helps! Let me know how it turns out.
 

Jake

Appliance Tech - Admin
Staff member
Joined
Aug 24, 2004
Messages
117,327
Location
McMullen Valley, Arizona
Thanks Prak for updating your thread and fixing your microwave.(y)

For others with this model here's the parts diagram and the switch locations:
(click to enlarge)
HMC80252UC.png

#410 is this switch:
00614767 Microswitch


#411 is this switch:
00631512 Switch


Jake
 
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