Appliance Repair Forum

Samsung SMH9187B

By BraveHelios - 1/3/2019 3:32:38 PM

Stumped a bit...
Microwave quit one day. It would operate but not heat anything.
Opened it up and tested componants with a multimeter. Tested fuses, door switches, relays, thermoswitches. Found a bad fuse and a bad thermoswitch (test for continuity). Looking them up...
Fuse is a 20A 125v/250v Fast Blow Ceramic Fuse, 6x30mm (1/4" x 1-1/4"), F20A 20 amp (AP4237587)
Thermoswitch is Samsung Part Number DE47-20059B (AP4580112).
Schematic shows bad thermoswitch as P122 which has a corresponding part number of DE47-20059A but that item is no longer available, supersceded by PNBigGrinE47-20059B.

Since installing parts, microwave now heats BUT exhaust fan now always runs on speed 2 and cannot be switched off. Fan can go up in speed to max (5), back can only go as low as speed 2 and not off.

Playing some more... if I completely disconnect the new thermoswitch, the microwave will heat and the fan works 100% correctly... it switches off and can adjust from 1-5 speed. I also connected the two wires from the thermoswitch, bypassing the thermoswitch all together and the fan stays at speed 2 and will not switch off (unit does continue to heat) much like if the wires were connected to the thermoswitch.

What am I missing? Why does the microwave work correctly with the thermoswitch disconnected? Why is the fan stuck on when I connect to the new thermoswitch or when I connect the wires together, bypassing the T-switch? Did I order the wrong T-switch? There is another T-switch next to the one that went bad (P-123) and that has a part number of DE47-20034A. Are these things interchangeable?

Any help is greatly appreciated. Thanks! 

By Admin - 1/4/2019 2:11:35 AM

I dont think you ordered the wrong switch but there are multiple components connecting to the fan on this microwave..three different t-stats alone... there could be e number of things leading to this issue and because it's a bit more complex and needs a good bit of time to research all the possibilities I would say try for a definite answer.. you did get the right parts but you still have two more micro switches and two more t-stats that are on the fan circuit so I really dont know is what I am saying. Just answer charges a fee avg $25 but as far as I know you do not pay unless you are 100% satisfied.. you might figure it out on your own and I applaud you for trying to do this yourself but it isn't a real easy thing to figure out.. I have seen field technicians back in my days walk away from this type of repair lol.
either way good luck and I hope you get it figured out!