Question about Intermatic GM40 - 24 Hour/7-Day Dial Electromechanical Time Switch - NEMA 3

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Replacing an old timer with a new gm40.

I currently have an intermatic timer that is not working properly. I have purchased an intermatic gm 40. I'm trying to figure out which wires go where on the new timer. I have 2 black, 1 white, and a ground. The terminals are labeled differently than the one I'm replacing. It's 120v single load.

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Here is the instructions for your unit:

Intermatic GM40

Go to page #4 for wiring instructions on 120v dual loads.

Hope this helps and please rate this!

Posted on Dec 09, 2008

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After lighting strike my grasslin gm40 only works manually are the relays fried?


1) Something is fried. Probably the electronics if relays turn on-off with override.
http://waterheatertimer.org/How-to-wire-GM40-timer.html
http://waterheatertimer.org/How-to-wire-Whole-house-surge-protector.html
http://waterheatertimer.org/How-to-wire-GE-15207-timer.html

2) Try moving dip switches to different voltage, and change wiring and voltage for possible work around.
For example if you are controlling 240Volt, then move dip switches to 120V and run neutral wire to timer and use one 120V hot leg from 240Volt circuit to power clock motor.

3) If timer module is not rotating, then remove module for identifying marks on back. Order new FM1 timer module.

4) There is no reset protocol for this timer, or surge protection. Timer has one year warranty against workmanship defect. There are no replacement circuit boards.

5) Buy cheaper-made GE 15207 timer at Home Depot. Then if timer goes bad, buy another timer and return defect in new box for refund. This gives timer owner unofficial extended warranty.

Feb 12, 2013 | Intermatic GM40 - 24 Hour/7-Day Dial...

1 Answer

I replaced an Intermatic T104 Timer but the clock only works when I turn the switch on


The problem is that you need a jumper wire to power the clock from one of your two hot wires (assuming the clock is 120V), because the clock is currently powered downstream from the switch built into the timer. The jumper wire needs to go from one of your hot wire inputs to the clock. Don't add a new wire, just move the existing jumper wire that is going from one of the output terminals to the clock, so that it goes from one of the input terminals to the clock.

Jul 24, 2012 | Intermatic T104R 208-277Volt 40-amp Timer...

2 Answers

How to wire GM40 timer to 240vac


This connection is for 240 volts ONLY on the Intermatic GM40.

The first thing you need to do is make sure the Input Voltage Dip Switch (IVDS) is set correctly for 240 volts. The IVDS switch is located to the left of the terminal strip and just slightly above it. 4 is set to OFF, 3 is set to ON, 2 is set to OFF, and 1 is set to ON.

The first wire of the incoming (LINE) 240 volt cable (pick one) is connected to "L1" (the 1st terminal screw on the left). Also jumper a wire from "L1" to COM (the 5th terminal screw from the left).

The second wire of the incoming 240 volts is connected to "L2/N" (the 2nd terminal screw from the left). Also connect one of the wires (pick one) from the outgoing (LOAD) 240 volt cable to the "L2/N" terminal.

Connect the second wire of the outgoing 240 volts to the "NO" terminal (the 4th terminal screw from the left).

If you not sure which cable is which, turn OFF the circuit breaker suppying the timer, separate all the wires, turn the circuit breaker back ON. The cable that is hot is the incoming (LINE). Turn breaker back OFF and wire as above.

Dec 01, 2011 | Intermatic GM40 - 24 Hour/7-Day Dial...

1 Answer

How to wire to 240vac


Copy following links to help identify correct wiring:
If you are wiring GM40 timer, be sure to set dip switches before applying power.
http://waterheatertimer.org/How-to-wire-GM40-timer.html
http://waterheatertimer.org/See-inside-main-breaker-box.html

Dec 01, 2011 | Intermatic GM40 - 24 Hour/7-Day Dial...

1 Answer

I need to hookup up a Grasslin GM40 timer controlling one load and a 120vac application. Just wondering if someone could verify the hookup terminals as I cannot read the schematic as it is mostly gone. ...


Open following links to identify timer and download manual:
http://waterheatertimer.org/Intermatic-timers-and-manuals.html#GM

GM40 can be used for 120V or 240V 277V applications for single-phase and some 3-phase applications.
For 120Volt, set all 4 dip switches to ON position BEFORE applying power.
ON position is pushed to left.

120Volt cable from breaker box has black hot and white neutral wire.
Black hot typically connects to terminal L1
White neutral connects to terminal L2/N
This action will power the time clock and relays.

Other terminals on GM40 are the relay terminals, and these terminals are dry.
Dry means they receive no power when wires are connected to L1 and L2/N.

There are two independent relays and each relay has 3 terminals: NC NO and COM.
If you are controlling one 120volt Load, then use one relay.
Run a jumper wire from terminal L1 to COM terminal.
So COM terminal is connected to Hot.

Cable going to 120V Load has black and white wire.
Connect black Load wire to terminal NO (normally open).
Connect white Load wire to L2/N.

Jul 19, 2011 | Intermatic GM40 - 24 Hour/7-Day Dial...

1 Answer

How do I wire a 220 volt two speed swimming pumpmotor using aground fault circut creaker


More information is needed.
Is the circuit breaker 240Volts or 120V?
Is the pump 240V?
What kind of switching timer is connected to pump?
What color are your wires?
Read information below and then add a comment.

Typically, the pump is 240Volts.
Pump is wired to mechanical timer with NO NC contacts for example GM40 series:
http://www.intermatic.com/products/ec%204%20layer/mechanical%20time%20switches/24%20hour%207%20day/gm40%20series%20multi-voltage%20time%20switch.aspx
http://waterheatertimer.org/Intermatic-timers-and-manuals.html#GM
The timer sends power to one speed or the other speed but not both speeds at same time.
Timer can be mechanical or digital.
Mechanical timer is used if pump is supposed to be ON at all times.
Digital timer like P1353 is used to control pump more exactly.
http://waterheatertimer.org/Intermatic-trippers-and-parts.html#P1353
See example1 for 240V
http://waterheatertimer.org/images/P1353ME-2-speed-motor-500.jpg
Timer is rated or set for 240Volts.

GFCI protected 240Volt line leaves circuit breaker and goes to timer. Then timer and pump are both protected.

Jul 09, 2011 | Light Switches & Dimmers

1 Answer

Lights come on but don't stay on even though the tabs are set for it to stay on say from 4-12 it will go off at 7:30. Someone got thier hands on this before i did---could the tabs have been broken if...


GM40 is commercial-grade electronic time piece with FM1 analog timer dial.
I bought a used GM40 once and the electronics were bad, so if this is a used timer, it might not function as expected.

I don't think the tabs/pins are broken. FM1 timer module is heavy duty.
Turning the dial clockwise does not damage timer. That's how you set current time and test timer.
Rotating dial counterclockwise is not possible without breaking the timer.
http://waterheatertimer.org/How-to-set-timers.html
http://waterheatertimer.org/pdf/Intermatic-Grasslin-gm40.pdf

FM1 analog timer module can be replaced if timer stopped working.
http://waterheatertimer.org/Intermatic-trippers-and-parts.html#FM1

If certain pins/tabs are broken, you might be able to work around problem by offsetting current time by 6 hours or 12 hours. Or you can move wires from NO to NC terminals and see if the relays are causing a problem.

To set FM1 timer, the pins are pushed outward or inward.
For example to turn on Load for 1 hour, then 4 consecutive pins are moved.
To turn on Load for 3 hours, then 12 consecutive pins are moved.
To test if pins need to be inward or outward, set some pins and then manually rotate timer dial clockwise and watch when the Load turns on-off.

Jun 19, 2011 | Intermatic GM40 - 24 Hour/7-Day Dial...

1 Answer

We have installed GM40 time. which control shaft on / off cycle i.e 4 hours on / 2 off. i checked selector switch postion, i.e continuous on (upper position) and continuous off (lower position) in this...


I have GM40 timer sitting in front of me.
I cannot understand your question because I do not know what the 'control shaft' is.
If you mean the black-colored FM1 clock dial with captive trippers, then this dial is supposed to rotate continually as long as timer has power.
http://waterheatertimer.org/images/FM-1-Grasslin-Intermatic-20.jpg

Grasslin/Intermatic GM40 page
http://www.intermatic.com/products/grasslin/electromechanical%20time%20switches/multi-voltage%20time%20switches.aspx
The manual says quote:
With the manual switch in the middle position, the GM40 is in automatic mode and will switch at the programmed times. In the upper position "I", the load is permanently ON. In the lower position, "O", the load is permanently OFF. End quote.
In any switch position, the FM1 clock dial will continually rotate.

If your Load does not turn on-and-off according to the trippers set on FM1 clock dial, then 1) wiring is suspect or 2) if dip switches are not correctly set before applying voltage, and timer could be damaged.

The timer arrives with dip switches pre-set for 277Volts.

You can also manually rotate clock dial clockwise to observe when the load turns on-off.

Add a comment and give more information.
I would like to know what the 'control shaft' is, and what voltage you are using, and what dips switch setting you have, and which wires are connected to each terminal.

Apr 13, 2011 | Intermatic GM40 - 24 Hour/7-Day Dial...

1 Answer

Timer is working but stops but stops at the on and off points like it don't have enough power to engage switch, timer is less then year old.


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The pins push the lever.

New T-104 comes with a bit of white grease on the lever.

The lever is connected to the manual override.
Click the manual override back and forth. It should click firm and crisp.
If the manual override is sluggish or it sticks, then timer might be bad ... buy a new T-104 and snap the new insides into the box without changing out the box ... and if you bought it at the local store, then return the new timer with the old insides.

If the manual override works crisp and clean, then the clock motor may be bad.
Clock motors and Intermatic timers run for years, but the clock gears are plastic.
You can buy a T-100 series 240Volt clock motor at WW Grainger for $16
http://www.grainger.com/Grainger/INTERMATIC-Time-Clock-Motor-1PNK2?Pid=search
I think you need a small star screwdriver to change clock motor

Finally, the main dial gears are steel. If timer is exposed to moisture and dirt, the gears can get rusty and that might cause dial to stall. Snap out the insides and clean out the dirt, spray a bit of WD-40. Turn off electricity because WD-40 is extremely flammable.

Up-vote if this information helped. Thanks for the feed back.

Oct 14, 2010 | Intermatic T104R 208-277Volt 40-amp Timer...

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