Intermatic WH 21 timer will not turn off. The

Only parts sold for WH21 timer are clock motor and tripper.
You might be able to find something on ebay... like old non-functioning timer
http://waterheatertimer.org/How-to-troubleshoot-Intermatic-WH21-timer.html

Gene

Water Heater Timers Save Money

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1) Copy following links:
http://waterheatertimer.org/images/WH-Off-pin-clip-washer-600.jpg
http://waterheatertimer.org/images/WH-lever-001-400.jpg
http://waterheatertimer.org/How-to-troubleshoot-Intermatic-timer.html

2) Examining the WH40 in my office, there is a clip washer that holds override lever in place against timer body.
This might be considered V-shaped spring.
Buy at local hardware store

3) Add comment and say what you discover, and attach photo

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

1) Troubleshoot walk-thru indicates that tripper is wrong, or timer mechanism is worn out:
Check that tripper is labeled ON, and compares similarly with old tripper, and is not worn down. Trippers are made of softer metal and designed to wear out before the timer mechanism wears out.
http://waterheatertimer.org/How-to-troubleshoot-Intermatic-timer.html
http://waterheatertimer.org/images/WH-lever-005-500.jpg

2) Buy new timer mechanism: If the new ON tripper does not push the on-off lever, then timer mechanism is probably worn out.
Buy new T104M mechanism, and change out with existing mechanism using thumb spring located top inside box.
http://waterheatertimer.org/Intermatic-trippers-and-parts.html#T100

3) How it works: The trippers rotate around on clock dial. Trippers come into contact with on-off lever, and trippers push lever.
On tripper pushes lever one direction. Off tripper pushes same lever other direction.
Each time the lever moves back and forth, the manual override also clicks with audible sound.
The lever moves a slide bar located on back of timer mechanism, and that action opens and closes electrical circuit.
http://waterheatertimer.org/images/Back-of-WH40-2b-500.jpg

4) Since any timer mechanism can fit into the T10404R control panel, you can also buy and install T104M210 timer mechanism with fireman's switch that turns off heater 20 minutes before turning off pool pump.
For 2-speed pool pump, the digital P1353 can also be installed, and this timer would replace both timing mechanisms in the T10404R. Non-electronic timers are more reliable.
http://waterheatertimer.org/Intermatic-trippers-and-parts.html#P1353

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6) Take a moment and rate answer for accuracy:
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For a price, expert works with you while you work on timer or any do-it-yourself project.
Fixya is always less expensive than a service call.

You posted under WH21 Intermatic timer.
Intermatic does not show parts for that timer except 156EB1945A tripper.
http://waterheatertimer.org/Intermatic-trippers-and-parts.html

Parts are not available for WH21 240V water heater timer.
Timer has 1 year limited warranty.
http://www.intermatic.com/customer%20service/frequently%20asked%20questions.aspx
WH21 is rated for 25Amps and works on water heaters up to 4500Watts.
Look at label on side of tank to see wattage.
WH21 is SPST and turns off one hot wire to water heater.

I ran a business for many years.
Cost of stocking, organizing, and shipping parts is near same cost as new timer.

Following page shows selection of replacement timers:
http://waterheatertimer.org/Boxtype.html

For example, I have tested WH40 and T104 and other timers that show on page.
Trippers and motors are available for Intermatic box timers WH40 and T104, so you can maintain these specific models for many years.
http://www.grainger.com/Grainger/timer-accessories/timers/electrical/ecatalog/N-8hi
WH40 and T104 timers are SPDT and turn off both hot wires to water heater.
Both timers will work on any wattage residential water heater

http://waterheatertimer.org/How-to-wire-T104-Intermatic-timer.html
http://waterheatertimer.org/How-to-wire-EH40-hot-water-heater-timer.html

Fixya answers questions.
NSI is responsible for Tork.
http://tork.com/tork/elecmech.aspx

Electro-mechanical timers make audible click noise when timer turns on-off.
T1101 spring is the time-carryover for power outage.

Buy another Tork T1101 and swap out insides without changing box:
Take photo of wiring before making changeover.
http://www.weisd.com/store2/tork/torktimer1.php

Replace Tork with Intermatic T-101 120V timer
T101R for weathertight
Amazon for T101
Aplus sells T101R

For help wiring T101
http://waterheatertimer.org/How-to-wire-T104-Intermatic-timer.html#T101

Go to intermatic.com/.../instruction%20manuals.aspx scroll down to your model number and click and there you are

The clock motor might have gone bad.
Open following link for WH21 troubleshoot
http://waterheatertimer.org/How-to-troubleshoot-Intermatic-WH21-timer.html

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Hi,
No that is not approved for outdoor use unless installed in a waterproof box...

I would have them change it is will not last long...

heatman101

Possible cause....Electrical power to Timer is turned "OFF" by the Timer