Replacing the Light Switch on a Pfaff 1200 Sewing Machine

One of the repairs most users can manage is replacing a broken light switch. It only requires screwdriver use and some patience. Replacing the push-button for the sewing area light is a moderately difficult repair because of the limited space, the short wires, and the way the power inlet parts fall apart.

WARNINGS:

You must reinstall the power prongs in their original positions. If you screw this up, you might permanently damage the motor, the light switch and perhaps yourself.
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Unplug the power cord before you start taking the covers off.
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The connectors are soldered and look sturdy, but don't bend them to get them out of the way, or forcibly yank them out of the switch.

Step 1: Getting to the Light Switch

The first part of the repair is getting to the switch:

Remove the presser foot and needle.
Unplug the power supply cord!
Remove the top, motor and base covers. You do not need to remove the freearm cover or the front cover.
Remove the two screws that hold the power input box in place.
Push the box to the left, into the base of the machine and gently pull it out the bottom as far as the wiring allows.
Save the top part of the light switch. It will be reinstalled.
Remove the screw from the box cover and pull it off.
If it doesn't fall out, remove the black shield that covers the ends of the wires and the circuit board.
If there is a nut and washer holding the switch in the box, remove it. (mine was shattered and fell off)
Gently tug on the circuit board until it is out of the box. The light switch may come with it.

STOP HERE AND LABEL THE WIRES AND BOX!

Notice which wire goes to which power prong slot. Label the slots and the circuit board with matching numbers, letters or something. You can see my numbers on the box in some pictures, the numbers on the circuit board are on the side that isn't in any pictures. No, I will not take it apart just for a better picture.

I didn't realize that the prongs would fall out, and had to go back to the pictures to figure out what went where.

Step 2: Wiring the New Switch

The wires have metal tips on them (like shoelace tips) that are held in the switch by set-screws, those tiny screws on the side.

if you are replacing with a matching switch, it's easy.

Loosen the set screws and gently tug the wires out.
Insert the wires into the holes in the new switch and tighten the set screws.
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NOTE: With a 2-in, 2-out switch, like the one shown, make sure that you insert the wires in the top holes or the bottom holes, but not one top and one bottom hole.
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If your Pfaff has 2 sets of wires going into its light switch (I think the 1222E does), move them to the same positions in the new switch, one wire at a time.

I don't know if it's necessary to be this picky, but it's the easy way to keep from getting confused.

Step 3: Stuffing It All Back in the Box

Because the replacement switch was bigger than the original switch, I had very little room to work. Even with the correct size switch, it will be tight.

I made a series of pictures showing where each component should end up. These are NOT sequential assembly pictures. During the actual reassembly I was too busy holding things in place to take pictures.

There are no pictures of the inside of the black cover for the power box. Sorry 'bout that.

TIP: The power box cover is a snug fit, and you have to get the ridge into the slot to hold the power prongs in place. Practice putting them together before you start reinstalling anything.

Remove the plastic retaining nut from the pushbutton switch.
Insert the switch through the hole in the power input box.
Reinstall the nut.
Insert each power prong into the matching slot, with the screws up.
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You may find it easier to insert prongs and then the switch. Whatever works.
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Slide the circuit board into its slot.
Place the thin black shield over the connections on the circuit board.
Place the cover on the input box, making sure you have the tab and slot aligned.
You may have to hold this firmly because the wires will push back.
Reinstall the screw that holds the cover on.
TEST THE PRONGS by plugging in the power cord to make sure they don't slide back in the box.
If they do, you need to take it apart and try again.
When you reinstall the cover, make sure the slot and notch are aligned.

Step 4: Putting the Box Back in the Machine

Almost done.

Put the box back in position, sliding it through the hole in the frame.
Reinstall the screws.
Plug in the power cord and test the light switch. I had to nudge the prongs down a bit.
If it works, reinstall the covers.
The visible part of the light switch presses onto the shaft of the switch from the top.

Step 5: What to Do If It Looks Different?

Although they are the same family, there are differences between machines. For example, the 1222 has a long skinny power input box with multiple power connections in it.

Don't panic. You can do this.
Check YouTube for videos that might show what you need to know.
Take pictures. Electrons are cheap.
- Take a picture BEFORE you remove screws.
- If you remove a screw that doesn't affect what you think it should, reinstall that screw before you remove another one.
- Take a picture BEFORE you remove a part to show it in the correct position.
- Take a picture AFTER you remove a part to show what is under it.
- Take a picture of anything you can, from all sides.
  I didn't systematically do this, and am missing some pictures that would have been useful.
If you remove a cover or part and it is not the right one, reinstall it before you move on to the next part.
Label all wires and whatever they connect to with matching numbers or color-coded tape.
- Take a picture of the wires before you remove anything.
- Remove and label one wire at a time.
Tape all screws to the part they were holding in place. I put them in small ziplock baggies.
You will see videos done by experienced repair techs who dump all the screws into one dish, but they have been doing it long enough to recognize which screw belongs where.