Question about Sharp R-1850A Convection/Microwave Oven

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Monitor fuse blows when unit is turned on. I tested the door sensing switch,secondary interlock switch and the monitor switch all tested o.k. is there something else that could blow this fuse?

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  • 178 Answers

You probably have a shorted High Voltage Capacitor. Be sure to short across the terminals before you put your ohm meter leads to it....... obviously, if it's shorted already.....no problem........

Posted on Sep 13, 2009

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Why it's not functioning?


see this causes and fix it.
God bless you
f the microwave will not work at all, make sure power is on at the outlet and test the electrical cord. Test the fuse and replace it if it is faulty. Also check the door to make sure it closes properly. Test and, if needed, replace the fan. If the oven doesn't cook or cooks only intermittently but the display is on, check the door interlock switch, the thermal cutout (see the Applaince Controls Fix-It Guide), and the fan, replacing parts that don't pass the test.
If the oven keeps blowing fuses, check for a faulty door interlock or monitor switch.

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Oct 02, 2012 | Microwave Ovens

1 Answer

R-820js wont heat


see this causes and fix it .God bless you
f the microwave will not work at all, make sure power is on at the outlet and test the electrical cord. Test the fuse and replace it if it is faulty. Also check the door to make sure it closes properly. Test and, if needed, replace the fan. If the oven doesn't cook or cooks only intermittently but the display is on, check the door interlock switch, the thermal cutout (see the Applaince Controls Fix-It Guide), and the fan, replacing parts that don't pass the test.
If the oven keeps blowing fuses, check for a faulty door interlock or monitor switch.

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Oct 02, 2012 | Sharp R820JS 900 Watts Convection ...

1 Answer

Dead, replaced fuse and it blew again.


The fuse is connected directly in series with the monitor switch. If it senses one of the door switches bad it will blow the fuse, this is there as an added safety to make sure the oven will not work without the door closed.

There are usually three and sometimes four door switches just inside and to the left of the control panel that are activated when the door interlocks with them. One of the switches is most likely bad. Typically it is the primary interlock which is on top. It can be checked with an ohmmeter, usually you can see it broken as the plunger will not go down or come up like the others.


May 10, 2010 | Maytag MMV1153A Microwave Oven

1 Answer

Servicer with a PLMV169DCD Fuse blowing Problem


For future reference, we regularly repair such control boards and displays for customers nationwide by mail for $39.95 postpaid in about a week or so with a one-year guarantee.

Here's the main service manual. Other versions are here and here.

It may be grease inside one of the switches or arcing conductors (usually due to opening the door while it's cooking) making it sticky.

This was made by Sharp, so the side panel should come off each interlock switch for inspection.

But looking at the schematic, the monitor switch cannot come into play under normal circumstances unless the door is shut and the secondary interlock (relay RY2 on the control board) is closed and (oddly, if the published schematic is to be believed) if the oven lamp relay RY1 is closed .

Everything seems to point to a bizarre problem like maybe an intermittent short of a wire to the chassis, perhaps where a wire passes through a hole or guide in the sheet metal.

Also, you might consider unplugging the hood vent motor and trying it.

Did you try it with the oven powered from another outlet?

Also be sure the neutral and hot are not reversed at the outlet and that the line voltage is correct.

Sometimes a loose neutral can be a factor. Test outlets in several area of the house to see if some are high and some are low. This can be dangerous, and the power company must be called.

If there is anything else on the same breaker, that can be a factor.

Good luck!

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

William E. Miller
prototech@usa.net
http://www.microwavedisplay.com

Nov 28, 2009 | Frigidaire PLMV169DC Microwave Oven

1 Answer

Whirpool convection microwave not heating properly MH6150XMS


Be sure when testing these switches that they are not 'in circuit' to get a valid reading. If the monitor switch does not open when the door is closed, it should blow the fuse when the cook circuit is energized. If the secondary interlock switch does not close to zero ohms, it won't complete the circuit correctly.

Jun 05, 2009 | Sharp R-1850A Convection/Microwave Oven

2 Answers

The closed door doesn't always hit the limit switches


I strongly suggest that you do not attempt to adjust the hinges.

The door switch mounts are either cracked or need to be adjusted.

Door switch mount trouble is usually caused by slamming the door.

This may be a little more info that you need and it's from a Sharp service manual, but the general principles apply:

1. Disconnect the power supply cord, and then remove outer case.

2. Open the door and block it open.

3. Discharge high voltage capacitor.

If the door sensing switch, secondary interlock switch and monitor switch do not operate properly due to a misadjustment, the following adjustment should be made.

4. Loosen the two (2) screws holding latch hook to the oven cavity front flange.

5. With door closed, adjust latch hook by moving it back and forth, and up and down. In and out play of the door allowed by the upper and lower position of the latch hook should be less than 0.5mm. The vertical position of the latch hook should be adjusted so that the door sensing switch
and secondary interlock switch are activated with the door closed. The horizontal position of the latch hook should be adjusted so that the plunger of the monitor switch is pressed with the door closed.

6. Secure the screws with washers firmly.

7. Check the operation of all switches. If each switch has not activated with the door closed, loosen screw and adjust the latch hook position.

After adjustment, check the following.

1. In and out play of door remains less than 0.5mm when in the latched position. First check upper position of latch hook, pushing and pulling upper portion of door toward the oven face. Then check lower portion of the latch Figure C-3. Latch Switch Adjustments hook, pushing and pulling upper portion of door toward the oven face. Both results (play in the door) should be less than 0.5mm.

2. The door sensing switch and secondary interlock switch interrupt the circuit before the door can be opened.

3. Monitor switch contacts close when door is opened.

4. Re-install outer case and check for microwave leakage around door with an approved microwave survey meter.

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

Dec 05, 2008 | Emerson MW8102SS 1100 Watts Microwave Oven

1 Answer

Do you test your commercial microwaves for leakage? What standards do you comply with as far as allowable leakage?


As per a similar manual:

1. Microwave leakage limit (Power density limit): The power density of microwave radiation emitted by a microwave oven should not exceed 1mW/cm2 at any point 5cm or more from the external surface of the oven, measured prior to acquisition by a purchaser, and thereafter (through the useful life of the oven), 5 mW/cm2 at any point 5cm or more from the external surface of the oven.

2. Safety interlock switches: Primary interlock relay and door sensing switch shall prevent microwave radiation emission in excess of the requirement as above mentioned, secondary interlock switch shall prevent microwave radiation emission in excess of 5 mW/cm2 at any point 5cm or more from
the external surface of the oven.

You need to be sure that if the meter comes with a styrofoam cone tip, that should be installed or it will give high readings.

Also, the meter should be calibrated periodically, typically annually.

If the meter gets dropped or bumped, that may throw it out of alignment.

The most common causes of excessive leakage are loose or misaligned door switch mounts or hinges and physical damage to the chassis of the oven.

The most common cause of the misalignment of door switch mounts is slamming the door.

I would be sure my meter is set up and calibrated, then I would be sure my door switch mounts are aligned & tightened properly.

From a similar manual:

1. Disconnect the power supply cord, and then remove outer case.

2. Open the door and block it open.

3. Discharge high voltage capacitor. If the door sensing switch, secondary interlock switch and monitor switch do not operate properly due to a misadjustment, the following adjustment should be made.

4. Loosen the two (2) screws holding latch hook to the oven cavity front flange.

5. With door closed, adjust latch hook by moving it back and forth, and up and down. In and out play of the door allowed by the upper and lower position of the latch hook should be less than 0.5mm. The vertical position of the latch hook should be adjusted so that the door sensing switch and secondary interlock switch are activated with the door closed. The horizontal position of the latch hook should be adjusted so that the plunger of the monitor switch is pressed with the door closed.

6. Secure the screws with washers firmly.

7. Check the operation of all switches. If each switch has not activated with the door closed, loosen screw and adjust the latch hook position.

After adjustment, check the following.

1. In and out play of door remains less than 0.5mm when in the
latched position. First check upper position of latch hook, pushing and pulling upper portion of door toward the oven face. Then check lower portion of the latch hook, pushing and pulling lower portion of the door toward the oven face. Both results (play in the door) should be less than 0.5mm.

2. The door sensing switch and secondary interlock switch interrupt the circuit before the door can be opened.

3. Monitor switch contacts close when door is opened.

4. Re-install outer case and check for microwave leakage around
door with an approved microwave survey meter. (Refer to Microwave Measurement Procedure.)

Please write back with more details if you need further help.

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

Aug 12, 2008 | Sharp Microwave Ovens

1 Answer

Fuse


The Interlock Monitor Switch is an added
safety check on the Primary and
Secondary Interlock Switches. If the
Primary and Secondary Interlock Switches
allow the oven to operate with the door
open, the Monitor Switch will blow the
fuse.

You can get more information about adjuting the interlock switch from this link

http://136.166.4.200/contents/Microwave/LMVM1935xx/LMVM1935xx_Service_Manual.pdf

sections 7-11 thru 7-12 discuss the door interlock adjustment that will cause the 20A fuse to blow if it isn't set up right. I hope this helps you...

Aug 03, 2008 | LG LMVM1935 Convection/Microwave Oven

3 Answers

JMC7000ADW Blows circuit breaker


I've had this problem twice with our microwave. The hint to where the problem lies is that the breaker blows when you open the door at times. Inside the microwave are three microswitches; primary and secondary interlock micro switches and an Interlock Monitor switch. The switches are supposed to shut down the microwave if it is running and the door is opened. But, I've found the upper primary switch can stick internal at times and when the door is opened the stuck switch will, because of the way it is wired as a safety switch, cause either the fuse or possibly the main circuit breaker for the oven to pop. The reason the stuck switch blows the breaker or fuse is when the door is opened the interlock switch will cause the neutral wire from the AC power to be applied to the Upper Primary Interlock switch which normally should be open when the door is opened, but if the switch is intermittent or the contacts weld themselves shut the neutral line is connected direct to the "hot" side of the power line through the fuse and thermostat. The first time my microwave failed the switch had melted the contacts together inside the switch and the second time the switch became intermittent and would blow the breaker to the over ever so often. I suspected the switch the second time this happened and utilizing an ohm meter I checked the switch several times by opening and closing the door and once in a while it would remain closed instead of opening when the door was opened. Of course while trouble shooting the power cord to the microwave must be disconnected and use all safety precautions when working around the high voltage areas inside the microwave. I wrote Jenn-Air about the bad switch and the way it is wired into the circuit, but never received any acknowledgement. I suspect these microswitches are under rated for the amount of current that passes through the switch, thus they overheat and eventually arc the contacts together. I hope this helps explain the intermittent problem and could explain many of the intermittent blown fuse problems I see in these internet help sessions

May 09, 2008 | Jenn-Air JMC7000 Microwave Oven

2 Answers

Panasonic NN-2501 Microwave Oven range hood


It is possible that the magnatron is bad but hard to say on a no heat problem without checking all components. A lot of model give 5-7 yr warranty on that part.

Oct 05, 2007 | Panasonic NN-S251 Microwave Oven

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