Can i buy parts to replace the internal parts? my timer works but will not click the tab light something is stripped.

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

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

T104M used WG1573 clock motor:
http://waterheatertimer.org/How-to-troubleshoot-Intermatic-timer.html
http://waterheatertimer.org/How-to-replace-Intermatic-clock-motor.html
http://waterheatertimer.org/Intermatic-trippers-and-parts.html#T100
The timer mechanism has metal gears, while the clock motor has plastic gears. If the metal gears get dirty and bind, it will strip the plastic gears.
Turn off power, pull timer out of box, Clean out timer with compressed air, and spray WD40, add a bit of white grease to lever where trippers make contact, then replace clock motor ... and buy another set of trippers to have on-hand since they are designed to wear down so timer will last longer.
If timer body is broken so dial does not rotate, then buy new T104 and snap new mechanism into old box. Buying whole T104 with enclosure is cheaper than buying T104M mechanism only.

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

Open following link for full troubleshoot steps, replacement trippers, useful links, warranties and tips on power packs:
http://waterheatertimer.org/Malibu-power-pack-stopped-working.html

Add a comment for more free help.
Also take advantage of fixya expert assistance live.
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 T101 Intermatic box timer.
If you have different timer, instructions below will not apply, so add a comment whith model numenr or description of timer.

1) Click manual override on-off to see if Load turns ON, and that override snaps crisp and clean and is not sluggish or hard to move.
If override is not functioning well, then timer is bad. Buy new timer.
2) If dial is rotating, note current time, and watch if dial is keeping correct time over full day.
If dial is running slow, the buy T100 series 125Volt clock motor.
3) If dial is keeping good time, then tripper might be worn and need replacement

Link below shows Intermatic T100 series parts:
http://www.grainger.com/Grainger/timer-accessories/timers/electrical/ecatalog/N-8hi

4) Add a comment for more free help.
Also take advantage of fixya phone service.
For a price, fixya expert speaks with you over phone while you work on timer, or any do-it-yourself project.

You posted under Intermatic raintight timer.
Add a comment with your model and brand and I have extensive files on timers.

The best diagnostic is the manual override.
1) Click manual override and see if Load (lights, fan, motor) come on.
If manual override clicks on-and-off crisp and clean, but the lights do not come on, check your electric power.
If the manual override does not click crisp and clean, then the timer may be rusty, or timer may need to be replaced. Buy replacement timer and swap out timer mechanisms without changing the box.
If the manual override works fine, and Load turns on-and-off with manual override, then the clock or trippers are next suspect.

2) Check if the dial is turning as time passes.
If the dial is not turning, then the clock motor is bad and you can buy a new clock motor.
If dial is turning, and manual override turns Load on-and-off, then the tripper pins might be worn out, and you can buy new trippers.

3) To buy replacement parts: Timer door has model number of timer. Timer clock located on back of timer mechanism has identifying numbers. You can snap out the timer mechanism using metal spring locate top inside box.
Grainger sells trippers and motors:
http://www.grainger.com/Grainger/timer-accessories/timers/electrical/ecatalog/N-8hi
Aplus sells motors:
http://www.aplussupply.com/intermatic/timermotors.htm
Intermatic sells motors:
https://www.intermaticstore.com/ASPI700W.pgm?task=menucntrl&menuopt=TM

I went here:
Remington.com
http://www.desaparts.com/index.htm

• Typed "M30016US" into the "Model #:" window, then clicked search.
• Click the M30016US - Remington Electric Chain Saw "View Model" link.
• Click "View Illustrated Parts Breakdown" think you want item 18, 113004-01, Internal Gear
• Click the 113004-01 - USE REPLACEMENT PART # 122513-01 "View Part" link.

Results follow:
Part #: 122513-01 Price: $24.00
Description: KIT, INTERNAL GEAR (MOD) 747 B/O
If this is what you need I suggest you order it soon.
RemingtonPower has stopped production and replacement pars are almost exhausted. Sooner or later a part you need will be NLA. HTH
Lou

The PB912M10 timer clock motor is not sold separately. Aug 2010.
If power pack transformer still works: buy cheap plug-in timer, set power pack to override, and plug power pack into cheap timer.
With receipt, power pack might still be under warranty.
Open following link for power pack tips and resources:
http://waterheatertimer.org/Malibu-power-pack-stopped-working.html

A pin thru the timer shaft can break, or the plastic teeth it engages in can be stripped.

It is not difficult to repair if you have the parts, but you can only get these from another timer- maker will not supply parts.

To take timer apart.
Take it out of the machine.
You will see two twisted metal tabs on the back and one on the front.
Carefully straighten the tabs and the timer will come apart as FRONT, BACK, CAM ROTOR

Gently remove the shaft and you will see what part has failed.-- replace.

Be very careful with reassembly not to bend the contact fingers.

There is an internal fuse inside. Need to find the cause for it blowing or it will just go again. Check the monitor switch and door switches. Eric

Well, I have the same problem. In fact, I just took mine apart (look for 4 screws on the back gray plastic) and found that the gears are stripped. About 3 of the teeth are broke off. I've been looking for parts on the Internet, but no luck yet. I'm afraid the only solution is to purchase a new timer.