Struggled to get the fob open following the manual instructions but came across the following link Volkswagen Key Disassembly

Battery replaced in 5 minutes:thumbup:

Perfect timing - my battery gave out on me today !

You guys must sit on your keys!

Had my mk 1 for 4 years, used for business use, never replaced the batteries in the fob!

ah ha 2032 battery, thats all i needed to know lol.

I changed my battery after 3 years of constant use because I wasn't getting 40 yards anymore. I also needed to be a bit closer to roll the windows down via remote.

Thanks for the link - worked a treat!  I hate having to invent wheels - I am not that clever!