20A Switch SPST

This SPST switch is a 20 A rocker with a black body, a red rocker and two quick-connect terminals. It’s Blue Alpine part E00112-00 and costs $3.88. One circuit, on or off. Nothing more to it than that.

What SPST means

Switch contacts are described by poles and throws. A pole is a separate circuit the switch controls; a throw is a position that connects it. Single pole, single throw is the simplest arrangement there is: one path that the rocker either completes or breaks. Count the terminals and you’ll usually know what you have.

• SPST switch: 2 terminals, one circuit, on/off
• SPDT: 3 terminals, one circuit sent to either of two outputs
• DPST: 4 terminals, two circuits switched together

If your old switch has three or four terminals, it isn’t this part, even if the front looks the same. A lighted rocker can also have an extra terminal for its lamp. The switch article has diagrams of each contact layout.

Why the 20 A rating matters

20 A is the current the contacts are rated to handle. Every time a switch opens under load, a small arc jumps across the contacts and eats a little of them away. An undersized switch wears faster, runs warmer, and can eventually weld shut so it won’t turn off at all.

So never replace a 20 A SPST switch with a 10 A or 15 A one, even if it drops right into the hole. A higher rating is generally fine electrically. A lower one isn’t.

Ratings are usually printed or molded on the side of the body, as amps and volts. Read your old one. If it shows something other than 20 A, ask us before you order.

Testing an SPST switch with a meter

With the machine unplugged and one wire disconnected, set a multimeter to continuity and touch a probe to each terminal. Rocker on should beep. In the off position it should read open. Flip it back and forth a few times and watch the display. A healthy SPST switch gives the same answer every time. Readings that flicker, a crunchy or mushy feel, or brown marks around the terminals all mean it’s finished.

Swapping out the SPST switch

A quick word on safety: this switch carries mains current. Keep the dryer unplugged the whole time you’re working on it, and hand the job to a qualified person if mains wiring isn’t something you’re comfortable with.

Take a photo of the wiring first. Pull each quick-connect off by its body, never by the wire. Then check how the old switch is held in. Many rockers clip into a rectangular cutout, so measure that opening and compare. On a plain two-terminal switch the terminals usually aren’t line or load specific, but put the wires back where they came from anyway. Push each connector on until it’s fully seated, because a loose quick-connect carrying 20 A gets hot fast.

Quick-connect terminals and connectors

The two terminals are flat tabs that take push-on female connectors. Quick-connect tabs come in a few standard widths, with 0.187 in and 0.250 in the most common. If you’re replacing the crimp connectors on your wires too, match them to the tab on the new SPST switch, not the old connector you happened to have in a drawer. Use connectors and wire sized for the current. Brown or brittle insulation on the old connectors is a sign they ran hot, and they shouldn’t go back on.

Is this SPST switch the one in my dryer?

We can’t say which model uses it, so start with the part number in your manual. If it reads E00112-00, you can order. If it doesn’t, send a photo of your switch and its markings through our contact page and we’ll take a look.

The power entry module and other electronics replacement parts are listed the same way, by Blue Alpine part number.