I need to change the battery in my vans keyfob as it never had one what size do I need( peugot expert)

Check the keyfob battery replacement section in your owner's manual. It might be the original key but there is a little circuit in the keyfob that allows the car to recognise the keyfob as the owners fob. When the keyfob battery is changed it loses this recognition info and has to be re-registered with the car. This involves a set of actions, like a little ritual, to get the key and car to 'handshake'.
Every make and model have different 'handshake' rituals. If you don't have an owner's manual there's a good chance you'll be able to find your ritual on Google. Good luck.

thats a dealer issue sorry..

1.)I would recommended that you ensure all key fobs are fitted with new batteries. ( Click here to see battery replacement guide).
2.)Get in the car and close the drivers side door.
3.)Put the key into the ignition and turn to position I.
4.)Wait 5 seconds
5.)Turn the key quickly to position II then back to I four times.
6.)You should hear a single chime.
7.)Remove the Key
8.)For each Keyfob in rapid succesion. Press any single button on the keyfob you wish to pair, you should hear a chime as each Keyfob is paired with the security system. After the chime do the next Keyfob.
9.)Check operation of each Keyfob.

See http://www.bluejag.co.uk/X-Type-keyfob-reprogramming.php

http://www.bluejag.co.uk/X-Type-keyfob-reprogramming.php

copy/pasted from the above link..

"Programming or pairing a new remote Keyfob for the X Type is a very simple job that will cost a substantial amount if it is done by Jaguar. It's annoying but this may need to be done if your Keyfob battery has been allowed to go flat, or the car battery has been removed for any length of time.
Follow these steps exactly and you should have no problems, pairing old or replacement Keyfobs for your car.

1.)I would recommended that you ensure all key fobs are fitted with new batteries. ( Click here to see battery replacement guide).
2.)Get in the car and close the drivers side door.
3.)Put the key into the ignition and turn to position I.
4.)Wait 5 seconds
5.)Turn the key quickly to position II then back to I four times.
6.)You should hear a single chime.
7.)Remove the Key
8.)For each Keyfob in rapid succesion. Press any single button on the keyfob you wish to pair, you should hear a chime as each Keyfob is paired with the security system. After the chime do the next Keyfob.
9.)Check operation of each Keyfob. "

Hope it works for you!

best advice i can give is to make a coca can gasket for the ERG valve so it blocks the hole off ,then it will run ok promise ,you do not this device and it will pass the mot without it ,nobody will even know its blocked off

call customer service for your car Brand and they can tell you how to reprogram or google your car and keyfob program.

Your key fob needs reprogramming, and yes the alarm will go off when you open the door, but you have enough time to put the key in the ignition which will prevent the alarm sounding. Car is usable until you get the fob sorted by locking and unlocking using the key.

ciphon it.

either change the battery or the alternator,,just either of those,,,if your battery is no good it wont hold charge when started,,,also if your alternator is no good it wont charge your battery when engine is running,,,(it can also drain your battery if faulty)..get a second hand alternator in a breakers yard maybe a batt too much cheaper,,,hope i helped you,,