Repairing a GoldStar microwave

My old microwave started to have a problem lately.

Sometime when turning ON the oven, only the light works, the blower and the magnetron remains turned OFF.

As usual ... CAUTION !!!
If you don't know what you are doing and how to work on appliances connected to the grid, DON'T DO ANYTHING ! Call a professional repair service !
Especially a microwave oven could be lethal if opened without taking precautions and knowing EXACTLY what you are doing.

The problem is an indication that a microswitch in the door latch, that has the purpose to remove power to the magnetron when opening the door, has issues.
Like every mechanical object, the life of a switch is limited.

The problem in detail

The microswitch is a security feature, and it is important to be sure is working safely.
The fact that so far the problem is limited to don't have the microwave starting as expected, could lead in future to be able to open the oven while running and not having the power cut to the magnetron !
Quite danger scenario.

The problem is easy diagnosed simply opening the oven door, closing it and start a cook cycle.
Only the light goes on, randomly also the blower and magnetron starts.
While running with no magnetron, pushing gently down the door, or keep it pulled with very low force, make the oven starts.

So the first suspect is the microswitch of the door.

Fast workaround

Since I discovered that pulling GENTLY the door allows the micro switch to work, until I receive the spare parts, I can have the microwave working simply putting a spacer between the door and the oven, like a double folded piece of paper.
Tadaaaaa :)

Of course better be sure that the spacer is not causing any leakage of radiation and if so, how much so to just stay away when the oven is working.
To know if the oven has a leakage a tool is needed. The tool can be simple like a fluorescent bulb or a specific designed one, is up to you and your knowledge.
I have a leakage detector tool.
Can be useful to read some FDA guidelines about microwaves and safety.

As usual my warmest suggestion is to don't do anything if you don't know exactly what you are doing and why !

My tests did show up that the spacer is not increasing the leakage of the oven so the workaround is safe.
Of course ... that just lasted few days. After few days (while waiting for the spare parts) the microswitch did die completely.

Finding the spare part

Especially for old appliances, is not always easy to find spare parts, and often not all the parts are anyway available.
There are many sites that offer spare parts for home appliances.
I started to explore three of them :

All these places have the spare parts I need and schematics of the oven (GoldStar MV1501W), manufactured in 2003, so about 15 years old oven.

A search for the door microswitch for GoldStar model MV1501W returned that actually there are 3 switches.

This is the schematic where the switches are :

All the places I visited had the switches so I just randomly picked up one place (Appliance Factory part) and ordered all of them.
Considering the age of the oven, is better to change all of them anyway since very probably they all reached the end of life.
For about 20$ (including the shipment) I could have the oven repaired.
If the problem is bigger than the switches, it make more sense to change the entire oven at this point.

Opening the oven

Of course even BEFORE to think to take apart the oven, unplugging it is the thing to do.

Then wait few minutes before to start to work on it and always before to touch anything, check with a voltage detector, like this one ------>

The good thing about this tool is the capability to reveal EMF, I did used it for example to be sure no high voltage was present when repairing the zapper.
Since in the microwave there are components that can retain electric charges for some time, even when the oven is unplug, better to be sure to don't put hands where high voltage is present and be ready to discharge capacitors with a thick screwdriver, just in case.
Fortunately I have to say that the guys at the GoldStar did a really good design so actually once opened the oven is quite safe, i.e. is really really hard to touch dangerous areas.
Still ... caution.

Changing the switches

Here few pictures taken during the switch substitution.
No need to remove the oven from it's place, the switch assembly is located near the controls.
So I had just to remove the grid and the remove the electronic control plate.
To do so is enough to remove 1 screw and push up the control.

Removal of the vent grid

The control board. 15 years old but well done

To work better, remove all the cables from the electronic control.
Quite easy, are just two connectors.

The switch assembly

The switch assembly detached from the oven and exposed.

The lower switches. They appears in good shape.
I'm changing them anyway

The upper switch, the broken one

I did change all 3 switches. The upper one, the one that controls the magnetron, was the broken one.
On the picture is possible to see how the button is basically stuck inside the switch.
The other two were still working but because the age I decided to change all of them.

The big problem repairing old appliances come with the plastic.
If the switch assembly broke, I had to change the oven since I didn't find a spare switch assembly.
The plastic with the heat and age, become brittle and is easy to break.
Only to remove the control panel I broke a plastic hook, another one come off from the vent grid.

Fortunately I was able to change all 3 switches without breaking any plastic support, so at the end of the change the glorious microwave restart to work.
If nothing mechanical (aka plastic) break down it could work for other 15 years :)

After replacing the switches I did put it back and verified that the door is still closing correctly and aligned.
Then I did check for radiation leaking, everything OK, still on normal values.

I think I will change it anyway in few years. For now it works just fine but newer ovens are more efficient and with a better control.
Yeah, I love to repair things but I also love to try new things.

For now, mission accomplished :)

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Sunday, August 19, 2018