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Hi, First of all, operating a microwave without an exhaust fan is a fire and possibly an explosion hazard. There are very high heats generated. The fan is operated by a control board relay. It can't be repaired. Failing control board needs to be traced, tested, and replaced. and it may not be the only problem.A schematic would be necessary but are not published due to danger of servicing high voltage circuits.
Unfortunately, it's not really a DIY project unless you're an electronics technician. If you are, the parts alone are in the $130 range. Here's the parts site.
Here's the situation. Much like televisions, microwaves are full of very high voltage (4000v-5000v) even when unplugged, and require care , schematic diagrams(unavailable to DIY servicers), and electronics experience to service. They are increasingly controlled by miniature pc boards and chips, impossible to repair, difficult to test, and expensive to replace. Also like televisions, once they're out of warrantee, parts and labor (if you can find them) can often approach or exceed the cost of a new machine. Therefore, like TVs, Microwaves have become cheaper to replace than to service, and service has become increasingly hard to find. You can check repair costs by clicking on SearsRepair for their plan. Cost could be weighed against cost of new unit with a new warrantee. It's up to you. I hope this answer is helpful if not welcome. Either way, let me know what you think. ed
Ed, I was not clear enough. NOT the exhaust fan inside the microwave, rather the hood fan/blower underneath for the stove/range exhaust (an option I think). There are four positions plus off. Currently the blower runs on the highest speed and cannot be turned off. I just bulled the wire that powers the blower.
The parts book shows two resistors (a 50 watt & a 25 watt) and I think one is for the blower and maybe shorted. Thus with no resistance, blower would run on high.
Am I close ?
Hi, we seem to have lost contact. I hope my answer was helpful. Let me know if I can help further. Ed
Your answer was helpful. I called both Sears & Whirlpool customer service to order the fan control, neither was helpful (actually they were awful), so I took a chance and ordered it anyway.
I'll report back when I have the control. Any idea how to open the microwave sheetmetal box ? I don't yet see anyway to access the control which is behind the buttons on the front. I've opened up the bottom where the ventilation fan is, no help. I'm persistent & mechanical.
The new fan control fixed my problem. Thanks again for your help.
Great news. persistence pays off. Glad I could help.
I still have a problem. The M/W worked for fine awhile except for the turntable. I didn't reconnect the two wires when reinstalling the bottom cover. When I open the cover, one of the hanging wires touched the cover and shorted. No power to the microwave touch screen now. The house circuit breaker didn't throw. I removed the 20 amp line fuse and it tested good on a simple continunity test (resistance).
Note sure if my fuse test was good ? I'll recheck the fuse (or get a new one) and see if the exhaust hood fan & lights work. I also check that I have power to the A/C filter. If yes, I'm thinking the primary or secondary interlock switches, the hood fan & lights do not go thru this circuit. Any other ideas ? The manual suggests if the 20 amp fuse blows the interlock switches need to be replaced.
Hi marvin, this is exactly the kind of problem I warned you against. It sounds like the touch screen has blown. fuses do not protect against accidental short circuits.That manual is a class manual for supervised study. i recommended very simple repairs. I can't supervise an untrained technician at a distance. There is a limit to remote diagnosis. I sincerely hope you are careful around the HV section. I hope you accept this answer. and I wish you the best. ed
Yes I admit I made a mistake and now I intend to fix it.
BTW, I'm a professional safety engineer. I don't want to pay the outrageously expensive Sears repair technicians to come to my home ... I've had some bad experiences.
I wasn't saying you made a mistake. I was concerned for your safety. I was not aware you were an engineer. I'm relieved to hear it. I know of some pretty serious injuries from hobbyists working on microwaves. I give a lot of warnings. I'm sorry if I insulted you. Since your trained, here's something else you may find useful. REPAIR FAQ It's dated but very practical. Read the section about interlock switches. You'll see that they're designed to blow the line fuse when they're misaligned as well as when they're blown. also check the turntable motor for continuity and touchpad pcb for burnouts. That's most likely. Let me know how it goes. ed
I have continuity on the turntable with some resistance. I have the door removed, how do I test the touchpad for burnouts ? There is a board and some panels.
I'm a mechanical engineer.
I've tested the interlock switches as good and the main inline fuse is good. Parts list show a LCD module and elec-control on the door. The trouble shooting guide says replace the LCD module first, what do you think ? I assume the LCD module is the display board (which is completely black) ?
Everything must go thru the LCD, the vent fan and night lighs don't work either. The circuit diagram I have is tough to follow becasue its not for a touch screen model.
Marvin, that sounds right. LCD means Liquid Crystal Display. check to see if it's returnable.ed