I have a problem with my 2019 model Whirlpool over-the-range microwave not heating up food or liquid. Everything else seems to run fine except the heating. Model is wmh32519hz3.
I have tested the diode, magnetron and capacitor which all pass the tests according to Repair Clinic's testing methods. What else could it be? The transformer shows no signs of burn damage or smell. I have not checked the door switches yet.
You need to check for 120vac on the primary side of the transformer when heating.
That's the low voltage side of the transformer.
Finding or not finding that voltage will dictate the direction to check.
I removed the transformer and measured resistance across the secondary winding lead and to ground (the mounting holes). I get only 0.3 Ohms. Apparently it should read 35 to 100 Ohms. Has my transformer shorted?
Interesting.... same tech sheet under two different numbers.
You'd know if your transformer was shorted. You'd get a bang.
I'll check it connected in the unit. If there is 120v on the primary and no heat... I know it's an HV problem.
Pretty new unit for HV problems.
Ok I'm getting 115 VAC when touching my multimeterleads to the two wire terminals coming off the primary winding.
It seems that my HV transformer is good.
Do you know the sound a microwave makes when it ramps up ?
When it first starts the HV is quiet and after a few seconds you can hear the transformer strain as the magnetron heats up and draws power. Do you hear that ?
A magnetron can check good electrically and be bad.
A cracked magnet is a rare but possible problem.
Yes, after about 4 seconds I hear a light buzz sound. Almost like a muted residential A/C compressor kicking on. Then it lasts for another 10 seconds and fade away.
I should have mentioned in my first post that the microwave started making a louder hum/buzzing noise whenever it failed to heat food.
When he refers to a "magtube" does he mean the magnetron? Also, he says to unplug the two wires to the magtube. These are the thick red and black insulated wires connecting the magnetron, yes? I assume you unplug the microwave, discharge the capacitor, disconnect the two wires, then plug it back in, and then run a cycle?
Yes... some sound like a light buzz.
When the filament heats up in 3-4 seconds it starts drawing heavy power.
If you have it set in normal or HI heat.... that buzz should not stop.
If it's stopping in 10 seconds.... that's pointing to a bad magnetron.
If allowed to continue running... does the buzz start again ?
After safing off the area and killing power....check the magnetron fins..... are they extremely hot ?
There should be a fan blowing thru the fins. If not and it gets too hot.... the thermal sensor on the mag will shut down the transformer until it cools off.
The magnetron is nothing more than a high power high frequency tube
I ran the microwave for 60 seconds and the light buzz noise came on after a few seconds and then faded away like before. But it stayed away for about 45 seconds. I could not feel any airflow through the magnetron's heatsink. There is a plastic duct that is on one side of the magnetron and it connects to the blower fan at the top rear.
No.... it's not normal. The mag should not get excessively hot.
Most microwaves have a small blower cooling the mag.
I only see the main blower and a series of baffles in yours.
I'm not totally sure how that cooling system works. It would appear by duct design that that the main blower is supposed to draw air in from/across the tube to cool it. The schematic doesn't show the blower running during microwave operation....does it run ?
There are unusual duct pieces shown. You're going to need to check for a clear airflow path.
make sure the airflow pieces are in place.
Yes the blower works fine. It moves a good amount of air out the top when the microwave is running. It blows into a small exhaust duct hidden in the cabinet above the unit and exits to outside the house. There is no fan dedicated to the magnetron just like your schematic shows. Maybe that's why it failed already lol.
I mean if you left your finger on the fins long enough you would be burned. The service manual mentions the mag tstat opens at 275 F and closes at 203 F. Or maybe the other way around. What does that mean?
Anyone know what this thermostat/switch is called? I've found similar but not with the button. It shuts off way too early in my water distiller. Also, want temp range? I assume something over boiling 100 centigrade, they have 40, 110, 150...so I guess it works by closing when hitting the button, then opening upon reaching the rated temp.
If I don't find one, , how would the ones without the button work? "On" when plugged in and under the rated temp? I was thinking til I find one I could operate it like that just connecting the wires and manually taking out the plug each time.
It's a sears distiller 625 345400 but it's so old doesn't look like there's any exact replacements around.
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05-25-23, 11:34 AM
