My Viking Professional convection/microwave oven does not heat up. Light comes on, fan comes on, turntable turns, but no heat.

I'm guessing that's a VMOS200?

If so, that's a rebranded Sharp R-530ES (as is the Dacor DMO2420S) and its secondary interlock (bottom door switch) or that switch's mount is bad.

See this file on door switches. If you only need a switch, you can order a universal type here for $5 postpaid.

The Sharp R-530E service manual will aid you in disassembly and it is here.

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

Sounds more like a thermal overload cut out has operatered rather than Elements or Magnatron if you have mutimeter you can check this easy...

See solution posted on Jul 30, 2009 by MicrowaveSvc This solution was right on target and got my microwave fixed in 10 minutes!

When you close the oven door the latches operate a couple of interlock switches that control power. It may be that one of the door switches is bad or out of adjustment. It's also possible that one of the door latches is broken so it's not hitting the switch. There should be two door latches. Are they both there? This oven could be fixed by adjusting or replacing the interlock parts as needed. Because of concerns about microwave leakage from an improper door seal, you should have this oven serviced by a professional.

David
This is a sure sign that the MAGNATRON unit has went out on your oven and will need replaced! (This is what cooks the food!)
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Thank You!

Check the door switch, when it is faulty the oven will turn on but turntable, fan and magnetron wont operate.

Regarding parts, contact the seller here to purchase parts.

You can also order from MicrowaveSvc , they also provide parts.

The fact that the microwave and convection both do not heat indicated that the oven is in demo mode, check the user manual, otherwise it will possibly be a relay not triggering, may need a pcb replacement, check Demo mode 1st....Phil

your magnatron needs replaced! (It may cost less for a new one then to fix this one!)

your microwave magnetron part is probably broken you need to send this to a shop im afraid, might cost you 40- 60 $
cheers

Most likely the bottom door switch. Dacor units are built by Sharp and that switch is a very common problem. You'd either need to check the switch with an ohm meter or remove the cover of the switch to see if it's burned inside.