Question about Intermatic Inc. ST01C Digital In-Wall Timer

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In the Intermatic ST01C, what is the function of the red wire in a two-switch set-up, which [after the second switch] goes to the same place as the [timer-switched] blue wire?

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1 Answer

ST01C is battery operated timer with red, blue, black & green wire.
Red wire is used when replacing 3-way switch (for ex: light switch at each end of hall)

Red wire is capped off when replacing single-pole switch.

If red and black wires are combined, lights will blink.

If red and blue wires are combined, timer reverses ON-OFF function (just like a 3-way switch reverses).

See wiring diagrams for ST01C

Posted on Nov 13, 2010


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Related Questions:

1 Answer

Intermatic light timer stopped has black and blue and red wires my wall box ha 2 black wires

Replace CR2 battery, then reset timer.
If functionality is not restored, then replace timer:


If you need further help, I’m available over the phone at

Apr 18, 2014 | Intermatic Inc. ST01C Digital In-Wall...

1 Answer

Wall timer makes lights blink

Timer is wired incorrectly.
Single pole wiring does not use the red wire. Red wire is capped off.
Copy following link to see specific wiring illustrations for ST01C timer:

Related but not same problem:
In some 3-way wiring installations, if the power goes out, or if the bulb burns out, the timer can click. The lights do not blink because power is out or bulb is bad. Simply flip the 3-way switch to stop clicking sound. Then change light bulb, or wait for power to resume.

If you need further help, I’m available over the phone at

Jul 04, 2012 | Intermatic Inc. ST01C Digital In-Wall...

1 Answer

2 switch system. 2 black wires and 1 red wire in the switch. I have hooked up black wire from the switch to the red wire in the box. green wire from switch to black wire from the box and red wire from the...

You posted under ST01C and are wiring timer to replace 3-way switch.
Open following link for specific illustrations:

1) The timer replaces one of the 3-way switches. The other 3-way switch remains, but must be rewired.
2) The timer must replace the 3-way switch that receives power from breaker box. It cannot replace the other 3-way switch. This is because the timer Black wire must always receive power.
3) The timer blue wire must connect to Load (light)
4) The ST01C red wire is only used when wiring for 3-way.
5) When the red wire and blue wire are connected together, they reverse the timer program. When timer red and blue are disconnected, the timer resumes programming. Connecting and disconnecting the red and blue wires is how the timer mimics 3-way operation.
6) The remaining 3-way switch must be wired so it will connect and disconnect the red and blue timer wires. So the remaining 3-way switch has to be rewired to meet specific timer wiring.

Jul 03, 2011 | Intermatic Inc. ST01C Digital In-Wall...

1 Answer

I have a 3 gang box: a is for hall light switch

Timer is not identified. Battery-operate timers wire differently than timers that require neutral wire.

For 4-wire battery-operated Intermatic EJ500, ST01C, and Ei600, Ei400 wiring:

For 4-wire Intermatic Ei200 series, KM-series, Ei500 that require neutral wire

Add a comment with model number for more specific information

Jun 19, 2011 | RTO Intermatic Digital 7 Day Wall Switch...

1 Answer

I have a Intermatic ST01C installed with a 3-way connection. The other day it started "clicking" on-off..on-off..on-off etc. and would not stop till I operated the non-timer switch leg in my...

Wiring could be suspect.
I have tested this timer.

ST01C works like this in 3-way circuit.
Timer program turns lights on-off.
When blue wire and red wire are connected together, then timer reverses on-off program.

So the only function of second 3-way switch is to connect and disconnect blue and red wires on the timer.
The second 3-way switch is wired differently than ordinary 3-way.
See illustration below.

Either the switch or timer have malfunctioned.
My bet is the timer.

1) Replace 3-way switch and see if problem clears up

2) Manual says: reset timer when encountering problems.
Hold down on-off button and push-and-release reset button.
Keep holding on-off until INIT displays.

3) You have to completely reprogram timer after reset.
Link above has ez steps.

ST01C manual:

Feb 22, 2011 | Intermatic Inc. ST01C Digital In-Wall...

1 Answer

Model ST01 to be used on a 3 way switch arrangement. Unit works in one switch position but fails to allow light to turn on in other switch position. Several other switches are adjacent in same box and...

You have ST01C timer.
If I understand correctly, timer is wired for 3-way and was working fine before.
Now, the timer is no longer letting the 2nd 3-way switch operate.

I tested this timer.
When the red and blue wires on timer are connected, the timer reverses.
When the red and blue wires are disconnected, the timer reverses back.
So the 2nd 3-way switch merely connects and disconnects the red and blue wire on timer.
This is why wiring is different on 2nd 3-way switch, and not like ordinary 3-way wiring.

This means that a) Timer has gone bad or b) 2nd 3-way switch has gone bad.

1) Replace 2nd 3-way switch

2) ST01C instructions say as last resort, reset timer.
However all timer programs will be lost.
Open following link to read steps for resetting and reprogramming timer, plus wiring diagrams.

3) Replace timer

Add a comment for more free help.
Also take advantage of fixya phone service.
For a price, expert speaks with you over phone while you work on timer or any do-it-yourself project.
Fixya is always less expensive than a service call.

Jan 30, 2011 | Intermatic Inc. ST01C Digital In-Wall...

1 Answer

What does the blue wire hook to

The blue wire always goes to Load (light fan motor)

If you have Intermatic ST01C or EJ500, see wiring illustration on following page:
If this is not your timer, then add a comment.

Wiring is dependent if you are replacing single pole switch or 3-way switch.

For single pole switch replacement:
Old switch has two wires.
Connect these wires to timer blue wire and timer black wire, in either order for now.
Green connects to bare ground wire.

Turn power ON.
Click timer on-off button.
If lights turn ON-and-OFF, then timer is wired correctly.
If lights do not turn ON-and-OFF, then reverse blue and black wires.
Timer red wire is capped off with wire nut

If your lights involuntarily blink after pushing ON-OFF button, then timer red wire is connected where timer blue wire should be connected.

For 3-way switch replacement, there is also a wiring diagram shown on link above.
Keep in mind that ST01C and EJ350 cannot replace a 3-way switch wire-for-wire.
Blue wire must always go to Load.
The other 3-way switch is also wired differently.
Add a comment with careful description of your wire colors and I will respond.

You can also take advantage of fixya phone support.
Fixya expert will walk you through the steps while you are wiring the device for a price.

Dec 26, 2010 | Intermatic & Self-Adjusting Wall Switch...

1 Answer

What color plug where i ve got three colors blue,red,black

If I understand correctly, you are replacing a switch with the EJ500 timer.
You mention a 'plug'

The EJ500 has 3 wires: Black Red Blue.
If you are replacing a single-pole switch:
The switch has 2 wires, one of these wires is the Hot-from-breaker and the other wire goes to Load:
Timer-black connects to Hot-from-breaker.
Timer-blue connects to wire-going-to-Load.
Timer-red wire is capped off. Red is not used for single pole switch.
If you connect wires and your lights blink, then you put the red wire where the blues wire should go.
If you connect wires and lights do not operate, try reversing the blue and black wires.

I posted images of EJ500 wiring (the Intermatic EJ500 and ST01C have identical wiring

If you are replacing a 3-way switch, the wiring is more complicated.
The EJ500 can not replace a 3-way switch wire-for-wire.
Diagrams on link above show wiring for 3-way.
Add a comment if you need more help.

Nov 10, 2010 | Intermatic EJ500C - Indoor Digital Wall...

1 Answer

My switch has only a white wire (hot) and a black wire (neutral). Witch one dose the red wire connect to?

I answer questions for free
I specialize in timers and electrical devices
If you have a different timer than the one shown below, add a comment with your timer model and I will help.
Different timers use the red wire differently.

You posted under Intermatic ST01C.
If the ST01C is your timer, then the red wire is capped off.
The black-timer wire connects to black wire.
The blue-timer wire connects to white wire.

IF the timer does not work after wiring, then try reversing the blue and black wires.

The following photo shows the EJ500 timer which is wired exactly like the ST01C

The following link shows several wiring diagrams for the ST01C and EJ500 timers

Nov 02, 2010 | Intermatic Inc. ST01C Digital In-Wall...

1 Answer

My timer has the lights blinking when it turns on

If lights are blinking with Intermatic EJ500 or ST01C, then you have the red and blue wires reversed. The red wire should be capped off. The blue wire goes to Load wire.

Aug 05, 2010 | Intermatic Inc. ST01C Digital In-Wall...

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