Sharp Microwave/Convection R-1875 not heating

[Pduggs]

It makes noise as if it’s working. Panel is lit as it always did. Light inside and underside are working. It is NOT heating and turntable is NOT turning. I pulled the fuse and it has continuity.
Is there another fuse somewhere? Could capacitor be the culprit?

Anything else I can do to determine the problem?  Thanks. 

[Wrayj1]

Ours did the same thing two years ago, magnetron went out, pretty expensive to replace especially in a 14cyrarvole microwave.  We purchased new, same model, but cut hole to vent to the outside to help keep heat out of the coach.

[Pduggs]

4 minutes ago, Wrayj1 said:

Ours did the same thing two years ago, magnetron went out, pretty expensive to replace especially in a 14cyrarvole microwave.  We purchased new, same model, but cut hole to vent to the outside to help keep heat out of the coach.

Thanks.

How did you determine it was the magnetron?

[CLIFF918]

Either the Mag or the capacitor has died. 

you can’t test the Mag . the capacitor you can check by testing continuity in both directions by reversing the leads on your meter should read low in one direction and   
high in the other direction and going lower . That would indicate a possible good cap.

Make sure you short both terminals of the cap with a screwdriver first just to be safe they hold a pretty good charge. Also it goes without saying “ unplug the beast first” be careful. 
Like Ray said the Mag is expensive to replace and you get new technology with a new oven.

Cliff

[Wrayj1]

As Cliff said, tested the capacitor, it was ok, had to be the magnetron.  You could save money by getting a non-convection. Thr biggest consideration is getting one with a similar pivoting door otherwise the door won't open.

[96 EVO]

When my capacitor went in the same unit, the fuse behind the control panel would blow immediately and all would go blank.

When the magnatron finally went, unit would keep running, just no heating.

I also replaced unit at that point.

[Harvey Babb]

DANGER! The magnetron works at several THOUSAND volts, as does the capacitor. Don't even think about trying to read the voltage at the capacitor or you WILL blow up your meter and run you run the REAL risk of electrocution. Before opening the case be SURE it's unplugged! The capacitor could hold a charge for quite a while so shorting across it with a screwdriver is a good idea before grabbing anything. (The charge stored will give a good "snap" when shorted so cover your eyes.)

As stated above the most likely culprit is the magnetron, although a loose connection is possible and there is also a rectifier in the circuit whose failure can give the same symptoms. If you can do without it for a few days you could order a rectifier (go by the type of connectors on the rectifier; they are all electrically the same). They go for about a dollar each, but you may have to buy a "lot" of 2 to 6. (Search "microwave rectifier" on Amazon)

The good news is that magnetrons are fairly cheap ($30 to $150) and easy to replace. Amazon carries a wide variety and they are almost always clearly marked with a part number. (Yes, if you get it done by a service shop you will pay dearly. I think you can figure out how that works!)

[Pduggs]

Thanks guys for your help. I have a rectifier coming and will check the capacitor after I short it.
 

Hopefully I don’t have to replace the oven, but I see the exact same oven available on Amazon for around $600. 

[Pduggs]

I checked the capacitor for continuity. My meter beeps and the reading goes to 0 on both terminals. I swapped the leads and get the readings that gradually go to 0 with meter beeping.

Does this indicate the capacitor is good?  

[CLIFF918]

Sounds like the cap is good. The Mag is probably the fault.

Cliff

[Ivan K]

I'd suggest considering a reasonably priced multimeter so you can actually measure the capacitance, useful for ac units too, beside inverter voltage, remote temp and much more. This is one for about $30 travels with us. Some clamp meters can do that too and can be useful. Takes the guesswork out.

[Tom Cherry]

1 hour ago, Pduggs said:

I checked the capacitor for continuity. My meter beeps and the reading goes to 0 on both terminals. I swapped the leads and get the readings that gradually go to 0 with meter beeping.

Does this indicate the capacitor is good?  

The ESL is a little rough.  But if you watch it a few times, it makes sense.  

Since you have the parts coming, you can test them.  I had a similar problem with a GE, not a convection, but the same basic circuit. I checked BOTH the Rectifier and the Capacitor....and I have a VOM with a Capacitor scale. They both checked the same. Put in the new parts and it worked. In retrospect, I think it was STUPIDITY on my part or my daughter's.  She said it quit....COLD turkey. I did the RESET and got power back to the display. BUT, I had already pulled out the parts.  

If you don't get it working, then the cost of the Magnetron and the installation is your choice. As long as you have power from the main PS and the fuses are GOOD, assuming that is where the fuses are, then you have eliminated everything buy the Magnetron. If that is it in the picture and you can easily remove it....then it is your call. BUT, there is, from what very KNOWLEDGEABLE folks that HAVE replaced a Magnetitron, a specific set of steps to ensure no radiation leakage. If this was a $250 or so unit....NOPE....but the Mag might not be that expensive....

Good Luck...

I assume that you mean...NO HEATING AT ALL. there is a fan switch that gave folks a lot of problems, and it would stop heating after maybe 59 seconds. We had a lot of folks that fixed theirs...

[Pduggs]

7 hours ago, Tom Cherry said:

The ESL is a little rough.  But if you watch it a few times, it makes sense.  

Since you have the parts coming, you can test them.  I had a similar problem with a GE, not a convection, but the same basic circuit. I checked BOTH the Rectifier and the Capacitor....and I have a VOM with a Capacitor scale. They both checked the same. Put in the new parts and it worked. In retrospect, I think it was STUPIDITY on my part or my daughter's.  She said it quit....COLD turkey. I did the RESET and got power back to the display. BUT, I had already pulled out the parts.  

If you don't get it working, then the cost of the Magnetron and the installation is your choice. As long as you have power from the main PS and the fuses are GOOD, assuming that is where the fuses are, then you have eliminated everything buy the Magnetron. If that is it in the picture and you can easily remove it....then it is your call. BUT, there is, from what very KNOWLEDGEABLE folks that HAVE replaced a Magnetitron, a specific set of steps to ensure no radiation leakage. If this was a $250 or so unit....NOPE....but the Mag might not be that expensive....

Good Luck...

I assume that you mean...NO HEATING AT ALL. there is a fan switch that gave folks a lot of problems, and it would stop heating after maybe 59 seconds. We had a lot of folks that fixed theirs...

Thanks Tom. I did have the 59 second issue a year ago and repaired it. This time the oven isn’t heating at all, but will run for as long as needed. 
 

I had run the oven for 90 minutes at 450 degrees to season a cast iron skillet, just before it stopped heating. Maybe the prolonged high heat did something to this old oven. 

[hitechpete]

9 hours ago, Pduggs said:

Thanks Tom. I did have the 59 second issue a year ago and repaired it. This time the oven isn’t heating at all, but will run for as long as needed. 
 

I had run the oven for 90 minutes at 450 degrees to season a cast iron skillet, just before it stopped heating. Maybe the prolonged high heat did something to this old oven. 

I just did a search on eBay.com for the magnetron shown in your photo, it’s only $65.00, for an original sharps unit.

[Pduggs]

We decided to buy a new microwave. I bought the exact same model on Amazon for $600. Hopefully it will install easily, but I have my doubts. I’m not certain the new one will have the same set up on the backside, with the two long angling screws securing the oven to the back wall. 
 

I pulled out the old one, which wasn’t too bad but took a little time. It wouldn’t come out, until I found one hidden screw holding it on the lower right side. I had to cut the power cord to get the plug out. The plug can’t be pulled through the hole in the adjacent cabinet because the electrical line encroaches on the opening. I’m not sure how Monaco did that. 
 

If anyone has installed a new oven, please offer any tips. 
 

PS. they claim the oven is 70lbs. This must be wrong. I handled it easily alone and carried it out of the motorhome and 30 yards to my car. I’m strong, just not that strong. Lol. 

 

Edited July 12, 2022 by Pduggs

[Tom Cherry]

24 minutes ago, Pduggs said:

We decided to buy a new microwave. I bought the exact same model on Amazon for $600. Hopefully it will install easily, but I have my doubts. I’m not certain the new one will have the same set up on the backside, with the two long angling screws securing the oven to the back wall. 
 

I pulled out the old one, which wasn’t too bad but took a little time. It wouldn’t come out, until I found one hidden screw holding it on the lower right side. I had to cut the power cord to get the plug out. The plug can’t be pulled through the hole in the adjacent cabinet because the electrical line encroaches on the opening. I’m not sure how Monaco did that. 
 

If anyone has installed a new oven, please offer any tips. 
 

PS. they claim the oven is 70lbs. This must be wrong. I handled it easily alone and carried it out of the motorhome and 30 yards to my car. I’m strong, just not that strong. Lol. 

 

my GUESS based on years of trying to get cords and cables and stuff into areas where the holes were too small. They installed the microwave and ran the cord through the opening. THEN the thinner piece of Romex (assumed) inside the plastic conduit....and then installed the outlet.  Others may know the real trick, but that one would work...

Good Luck...  As to your CORD issue....Unless you decide to remove the outlet....which I would really consider....and install a REAL 15 amp outlet, then you will need to either add a J-Box for an NEC approved splice....or do what I do, frequently.  Use THREE BUTT connectors and stagger them so that none overlap each other and then two wraps (or more) of electrical tape.  The Butt Connectors will withstand the vibration of the MH.  If you are really OCD or Anal, then put on a piece of shrink wrap tubing and cover your handi work. One of my "Certified" (NC Licensed) electricians would do this and hide the splice behind an item like a refrigerator....who's line cord was bad. The OSHA inspectors were notorious about not having an extension cord for any item in the break room and not allowing surge or CB protected power strips.  EVERY device had to be plugged in to an OUTLET...  So, we just ordered a replacement 90 deg line cord set....about 5 feet longer and then he spliced it using the above and tucked it in behind the fiber panel on the rear of the refrigerator....

 

[Pduggs]

I think I will just cut the hole larger so that the new plug can fit through the hole. 

[Tom Cherry]

22 minutes ago, Pduggs said:

I think I will just cut the hole larger so that the new plug can fit through the hole. 

Spoil sport....that takes all the fun and creativity out of it.  The fact that the hole is hidden and no one will ever know, save the little mouse that can now crawl in, is irrelevant.....  LOL...  Seriously....look at the Outlet and think about a surface mounted Jbox and a REAL Residential 15 Amp outlet...  Then cutting would be unnecessary if my method of installation is correct...

[Pduggs]

But I never had any trouble with the outlet Monaco installed. What are the benefits of installing a real 15 amp outlet?

[CLIFF918]

I went a few steps further and made mine vent outside.

[Pduggs]

I really like that idea, as the oven generates a lot heat when cooking something for a long time. I’m afraid though to cut through the side wall. How can you be sure you don’t hit electrical wires or a wall stud?

[Frank McElroy]

Your Dynasty has a steel frame body but I believe that the slides are an aluminum frame.  Depending on where the Microwave is mounted, use a strong magnet to see if there is any steel structure in the wall area where you want to put the vent opening.  But if your microwave is on a slideout, take a picture of the exterior wall when morning dew condenses on the outside skin just over the cooler metal structure.  There are a number of vertical, horizontal and diagonal metal structure elements in the walls. 

Attached is a morning picture of my model Dynasty Diamond IV showing the metal frame under the fiberglass skin of my front slideout.  On my coach, the microwave oven is to the rear of the small window above the sink.  That area is open and I could install a vent if I wanted to.  I'd first make a shallow interior cut to removed the interior wall covering first to expose the wall insulation just to be sure that I didn't miss anything in the wall before cutting through the outside wall.

[Pduggs]

I installed the new oven today. Easy install by one man. Ingenious design for attaching to back wall. Two long angling screws hold the oven. I may add a couple screws on the side, screwed into the cabinet for added support. 
 

[96 EVO]

Just make sure you don't run screws into something important.

If I recall, there's a cooling fan on the left hand side of the cabinet.

[Tom Cherry]

On 7/12/2022 at 6:49 PM, Frank McElroy said:

Your Dynasty has a steel frame body but I believe that the slides are an aluminum frame.  Depending on where the Microwave is mounted, use a strong magnet to see if there is any steel structure in the wall area where you want to put the vent opening.  But if your microwave is on a slideout, take a picture of the exterior wall when morning dew condenses on the outside skin just over the cooler metal structure.  There are a number of vertical, horizontal and diagonal metal structure elements in the walls. 

Attached is a morning picture of my model Dynasty Diamond IV showing the metal frame under the fiberglass skin of my front slideout.  On my coach, the microwave oven is to the rear of the small window above the sink.  That area is open and I could install a vent if I wanted to.  I'd first make a shallow interior cut to removed the interior wall covering first to expose the wall insulation just to be sure that I didn't miss anything in the wall before cutting through the outside wall.

Had a former member that vented his Sharp.  He tried this cheap vents like you would purchase at Lowes.  He did not like how the vent was going to look nor how the duct work was mating up.  He went to a Tiffin dealer or called and ordered the kit that they used….theirs, circa 2010, were all vented.  He cruised around the vary CG as a full timer and figured that out.  He followed Frank’s advice,, it was on a slide out, and did not hit anything and then used the paint codes and had an auto paint supplier mix the exterior color and then filled a small aerosol touch up can.  This is commonly done but you have to find a knowledgeable paint distributor. He sprayed it and you could barely see the difference.  This guy was a fabricator and craftsman.  He then pulled out the guts of the storage cabinet above the microwave and found a small wine cooler in a cabinet and then did some wood work on the face and hand fitted it. It looked factory.  So, he knew his “stuff” and planned and was meticulous…l