What Model and Year is your vehicle? For a VW Golf (Mark IV 2000), Place the fob with the VW logo upwards. Prise apart the sleeve with the aid of a screwdriver along the join in the middle of the fob. One section has the key, the other has the transmitter. Gently prise open the transmitter top to access the battery which is in the lid. The battery can be easily removed, but note the orientation. A plus (+) sign is shown on the lid to indicate the way the new battery should be installed.
You normally do not have to reprogram the key when you replace the battery. If you do you will have to contact your VW dealer.
The dealer
Need the year and model VW to answer the question.
Volkswagen Key Disassembly
Stock battery is a 6-volt unit. check VW specialty shops for replacement.
This procedure works on the VW 'switchblade' style key fobs. These key fobs are rectangular with a button on one side. When the button is pressed, the metal key flips out into the straight position, similar to a switchblade. To replace the battery: 1. Press the button to flip out the key. 2. Turn the key fob so the metal key stick out to the right and the channel that the key fits into is facing you. (The VW logo on the fob will be facing up) 3. Look closely inside the channel. It is split vertically. On the left hand side of the vertical split, it is also split horizontally. 4. Insert a flat head screwdriver into the vertical split and twist. They key fob will split along the vertical line separating the battery compartment (on the left) from the key (right). 5. The battery compartment (left) can now be pried open along its horizontal split. 6. The replacement battery is a 3 volt CR2032 lithium 'button cell' and is commonly available. 7. Replace the battery with the + side facing down. here are some photos http://www.riskin.org/vwkey
I assume you mean the car key with the flip button. step one: Yank it apart, grab both ends and pull longways until it comes apart. step two: Pry the bottom part in half with a screwdriver or butter knife. step three: You should see the battery now, take it out and take it to a drugstore/Walmart and get a replacement.
Use your key to unlock the door.
If you have a working key, go to Home Depot. Their key vendor makes a blank that'll fit in a VW.
dealer has to do this. A good locksmith may be able to also.
go to radio shack
timingbelt replacement vw 1.3