Microwave not heating items, also range vent not operating

Check to see if there's a relay providing power to the fan. If there is, the contacts might be sticking in the closed position. Assuming that this is an over-the-range unit, disconnecting the vent fan completely might not be a good idea as heat/steam from foods cooking on the range would more likely damage the microwave.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/david_29ad5d1dd86564b0

you may find the old unit was lower watts so took longer & cooked/heated better all the way through. a way to fix this is lower temp settings or pause and stir the food to help heat it up more even.

Your magnetron is overheating, which can be caused by:

• operating oven without cover(s) in place
• wrong magnetron installed in oven
• an old or otherwise failing magnetron
• cracked magnetron magnet
• improper power line voltage (should be 110-125VAC)
• foods low in moisture (popcorn & bacon, e.g. - add 1/2 cup of water in rear oven)
• failed or inoperable cooling fan or hood vent exhaust fan
• deteriorating foam weatherstripping seals in air ducts or on outside cover
• blocked air vents (dust, animal nest debris, insufficient free air space behind & around oven, etc.)
• clogged or greasy charcoal filter or grease filter
• blocked duct in hood vent exhaust

The first suspects in my book are fan failure, blocked vents, or bad magnetron.

Foods that are low in density or low in moisture (such as bacon and popcorn, respectively) can cause the magnetron to overheat.

That's because there is not enough of either mass or moisture to absorb enough of the microwave energy put out by the oven.

The excess energy then reflects back to the magnetron and causes a standing wave (like a poorly tuned transmitter antenna) and causes the magnetron to overload and overheat.

When the mag gets too hot, it trips the magnetron thermostat, a protective device which rests when it cools.

If this overheating is a persistent problem, a stopgap is to put about 1/3 to 1/2 a cup of water in a microwave-safe container (a Pyrex measuring cup is ideal) in a REAR CORNER of the microwave whenever you cook such items. This will help absorb excess energy, but you may have to increase cooking time just a little.

And of course I always suggest that food items be placed off-center in the microwave, NOT in the center of the turntable, otherwise the food is not exposed evenly enough to the microwave energy and will not heat as efficiently as it could.

(Placing it in the center is sort of like stirring paint by twirling a stick in the center instead of pulling it around in a circle in the paint can).

Such inefficient heating wastes the energy at best, and at worst it puts a strain on the magnetron.

If a magnetron is repeatedly subjected to such stress, it will prematurely fail. It will also draw excessive current, which can strain the high-voltage transformer.

That in turn will often lead to the oven's drawing excessive current, resulting in a hot cord and plug, and the fuse will blow - hopefully before the transformer or magnetron does!

An overheating magnetron can be due to:

• operating oven without cover(s) in place
• wrong magnetron installed in oven
• an old or otherwise failing magnetron
• cracked magnetron magnet
• improper power line voltage (should be 110-125VAC)
• foods low in moisture (popcorn & bacon, e.g. - add 1/2 cup of water in rear oven)
• failed or inoperable cooling fan or hood vent exhaust fan
• deteriorating foam weatherstripping seals in air ducts or on outside cover
• blocked air vents (dust, animal nest debris, insufficient free air space behind & around oven, etc.)
• clogged or greasy charcoal filter or grease filter
• blocked duct in hood vent exhaust

Some interesting reading on page 8 of the owner's manual:

"Boilovers cause smoking and greasy spillovers that may ignite and spread if the vent fan is operating.To minimize automatic fan operation, use adequate sized cookware and use high heat on surface units only when necessary."

And on page 20:

"If the temperature becomes too hot around the microwave oven, the fan in the vent hood will automatically turn on at the LEVEL 2 setting to cool the oven. The fan will automatically turn off when the oven has cooled down sufficiently. This is an automated process and cannot be turned off. The fan may stay on for 30 minutes or more after the cooktop and microwave controls are turned off. The Vent Fan will only operate in 1~4 levels modes while the microwave is working."

"Using the Vent delay off button
1. Press the Delay Off button once to turn the fan off after 1 minute.
2. Press the Delay Off button twice to turn the fan off after 3 minutes.
3. Press the Delay Off button three times to turn the fan off after 5 minutes.
4. Press the Delay Off button fiour times to turn the fan off after 10 minutes.
5. Press the Delay Off button five times to turn the fan off after 30 minutes."

If for some reason you don't have your owner's manual, you can still download it free here.

We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer

If it goes dead for a while during or after cooking then comes back on, the magnetron is probably overheating and causing the magnetron thermostat to open.

Then when it cools, it closes the circuit and allows power through again.

An overheating magnetron can be due to:

• operating oven without cover(s) in place
• wrong magnetron installed in oven
• an old or otherwise failing magnetron
• cracked magnetron magnet
• improper power line voltage (should be 110-125VAC)
• foods low in moisture (popcorn & bacon, e.g. - add 1/2 cup of water in rear oven)
• failed or inoperable cooling fan or hood vent exhaust fan
• deteriorating foam weatherstripping seals in air ducts or on outside cover
• blocked air vents (dust, animal nest debris, insufficient free air space behind & around oven, etc.)
• clogged or greasy charcoal filter or grease filter
• blocked duct in hood vent exhaust

We have a sound clip of what a microwave should sound like when the cooling fan and high voltage section are operating here.

It is vital that the cooling fan runs, or the magnetron will be destroyed. Repeated shutdowns like this are endangering the magnetron, assuming it's not bad already.

Your owner's manual will cover checking the filters and will cover warranty terms. The magnetron may still be covered.

If for some reason you don't have your manual, you can download it here.

We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.

William E. Miller
[email protected]
http://www.microwavedisplay.com

If it operates as normal but items don't seem to get hot it probably is a Magnatron failure (microwave producer). More times than not the repair / replacement of a Magnatron these days is not worth the investment, especially if the microwave is 4 years old or older ! You should be able to replace your microwave with a similar featured microwave / hood for about $300 to $400. You might try a JVM1750DMWW by GE great micro/hood for about $300, includes one touch sensor cook capabilities,300 CFM vent fan,removable rack,option to turn the turntable on or off, 1000 watts of cooking power. Good luck !

I had the same problem with mine, and discovered, somehow, that when I manually turned on the "vent fan", the microwave worked fine. A bit of a pain, but it heated up the food when it hadn't been prior to the vent fan being on. Can't understand why it solved it, but it's been working like that for about a year now. When I forget to turn on the vent fan though, the food is just as cold as when I put it in.

is the turntable working