Over the range Frigidaire Microwave not heating. Model FMT148

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AUTHORIZED DEALER Frigidaire Gallery Series
FGMV155CTF
30 Inch Over the Range Microwave Convection Option Sensor Cooking SpaceWise® Rack
4.4 Average rating of
73 reviews
color: smudge proof stainless steel
Smudge Proof Black Stainless Steel FGMV155CTD
$569.00 Smudge Proof Stainless Steel FGMV155CTF
$519.00 product highlights
Optional Built-In Trim Kit Convection Sensor Cook quick specs
Dimensions
Width: 29 7/8 Inch
Depth: 15 7/16 Inch
Height: 16 13/32 Inch
Features
Capacity: 1.5 Cu. Ft.
Cooking Watts: 900
View more Frigidaire 4 Piece Kitchen Appliances Package
Get the bundle for just $3,44800View the Bundle Recommended Accessories Available Colors/Finishes Stainless Steel (FGMV155CTF) Black Stainless (FGMV155CTD)
Frigidaire GALLERY™ 1.5 Cu. Ft. 900W Over-the-Range Convection Microwave

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Model No: FGMV155CTF

Features:

• 170/300 CFM 2-Speed Exhaust Fan
• Convection Option & Sensor Cooking
• Express-Select™ Controls
• SpaceWise™ Convection Rack
• Effortless Clean™ Interior

I have one same model for sale $100

If everything is working normally, except for heating, the likely cause is the magnetron.  Microwaves can be dangerous to work on, as the site below points out.  If you have an ohmmeter, it is possible to check the magnetron, but be certain to follow the precautions outlined at the webpage:
http://www.gallawa.com/microtech/mag_test.html

It sounds like the micro generator has died.

Yes, you should buy a new one as the cost of repair is likely to be high.

Please check the door switch for proper operation.

See this file.

In all likelihood the mangnetron has failed, or perhaps even something in the Power Supply. or a fault that is shutting the system mangnetron down, for safety reasons You need to have it serviced by a reputable service centre/man. Ensure you get a firm "Quote" before proceeding, and remember these days the cost of repair can equal or exceed the price of a new one.

The turntable system typically consists of the motor, the coupler, the turntable support with rollers, and the tray.

Here is a video of how a turntable motor should sound when you rotate it by hand.

If yours is not set to be off via the control panel, and it won't rotate or it sounds like it's grinding, etc., you may have a bad motor or plastic coupler.

To replace either, you need to unplug power, then remove the bottom cover of the oven.

You can find links to helpful exploded view diagrams and part ordering help here.

But if you've recently had trouble with the cooktop lights, then the control board may be damaged.

We regularly repair these control units for customers nationwide by mail for $39.95 postpaid in about a week or so with a one-year guarantee.

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

give more time

Does the turntable rotate? If everything but this works (except no heat), you probably have a bad door switch. Here's a discussion of what's involved in replacing it: http://www.fixya.com/support/t267796-kenmore_microwave_hood_combination_over

If the turntable does rotate, I'd suspect a more significant failure, such as the transformer, capacitor, or magnetron. If it's any of these, it's time to replace the unit.