No power. Checked AC connection and have power

There are fuses inside the unit. No internal breaker. A lot of the time that damages the main circuit board too. Blowing the trace that supplies the power to the bulb off of the board. will probably need a new baord, or someone to repair that one.

It sounds like the magnetron may have either failed or is not being supplied with the extremely high voltage required to run it.

YOUR SAFETY IS PARAMOUNT

This is a job for a professional but if you are safety clued up, here's instruction.
Make sure the !!!!capacitor is discharged!!!!! before attempting any sort of repair.
Check the door interlock switches first then the high voltage diode with either an AVO model 8 or moving coil meter on high resistance range for short circuit, (DVM's won't show the fault!), the capacitor can fail and go short circuit, the feed fuse on the primary of the high voltage transformer and then finally, the magnetron is best checked by substitution.
Hope that helps.

Dead appliance, power on wall outlet.

YOUR SAFETY IS PARAMOUNT!

Attempt this only if you are competent.

If your appliance has absolutely no functions at all, remove it from the mains supply, remove the case and see where the mains lead goes in to the appliance and follow the cable until you find the main fuse.
ONLY USE THE SAME TYPE AND RATING OF FUSE TO REPLACE IT.
The usual cause of this fuse failure is the door switches are contaminated or sticking. Check the door switches before putting power back on to the appliance.
Hope this helps.

All units have an internal fuse. Of course the unit is still plugged in. Check in the cabinet above the microwave.

We see (and repair) this a lot. The problem is on the control panel, which we regularly repair nationwide by mail for $39.95 postpaid in about a week or so.

This light failure often occurs when a bulb goes out and the filament shorts, or when the bulbs are removed or installed without first unplugging the oven from the power line. Either can cause such a failure on the controller.

This can often also affect the exhaust fan, cooling fan, turntable, and/or inside light operation, too.

Details of our service are at our Web site, along with a video showing how to remove a typical over the range control panel assembly in under 5 minutes.

Feel free to contact me directly with your brand, full model number and symptoms.

In rare cases, it may just be a blown fuse. There are 2 or 3 in this model.

There should also be a "mini-manual" hidden inside the unit behind the control panel or hidden on the left side behind the grille, which is very helpful when troubleshooting, & testing.

At our Web site, we have a video available showing how to remove a typical over the range control panel assembly in under 5 minutes.

If you don't find your mini-manual, or if you want to look at it before removing the controller, you can download it here (just enter your model number).

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

by replacing the fuse you meant the house circuit fuse or the microwaves internal fuse? and by conncetions your talking the internal wiring inside the case of the unit or wiring from the plug? if not its your 15 or 20 amp ceramic fuse inside the unit,if thats blown replace,but chk h.v.diode,v.v. cap,triac,control board, mis-adjusted interlock safety door switch,and lastly the mag could be defective

There are 3 fuses in that microwave. I had a similar issue. The one that I had to replace was the little ceramic fuse that is in line after the big fuse which is connected to the main line.
I couldn't find the ceramic fuse but I replaced it was a glass one about a year ago and it has been working since then. The fuse if located on the right front panel.

A microwave can be dead for many reasons.

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.

If it's intermittent or random, it may be a bad connection, usually on the control board or a loose fuse holder, or even an intermittent fuse.

You should do a continuity test the fuse while it's in the holder (with the microwave unplugged, of course) then turn the fuse by hand or take it out and put it back in, then test it again. If you remove the fuse, then press the meter leads against the ends, it can allow internal contact to be made and make a bad fuse appear to be good.

If it went dead almost immediately after pressing the Start pad, that's usually a shorted high-voltage capacitor.

If it went dead a few seconds after pressing the Start pad, that's usually a failing high-voltage transformer.

If it goes dead or blows the breaker when you plug it in or open or close the door, then there's a problem with a door switch or door switch mount.

If the fuse is good, it may be an open thermostat or thermal cutout on or near the magnetron or on top of the cavity / body of the oven.

If you or someone you know decide to look into it, we have critical safety information and disassembly information at our site, and our link is at our listing here on FixYa: http://tinyurl.com/yzjozk

You can usually find helpful exploded view diagrams and order parts by entering your full model number here: http://tinyurl.com/gv383

There should also be a "mini-manual" hidden inside the unit behind the control panel, which is very helpful when troubleshooting.

We're happy to help and we appreciate your thoughtful rating of our answer.

My Whirlpool MH3184xps is shooting a spark when in use with the rack. When the rack is removed the oven works fine. I am guessing that some of the coating on the rack has cracked and peeled and is exposing some aluminum. Has anyone else had this problem?

I had the same problem and fixed it with the help of others in this forum. There's a 250V 4A slow-blow fuse in a holder in one of the wires running from the main circuit breaker.  Just behind the upper end of the control panel.  Replacing said fuse got me running again.