sorry to resurrect this from the dead but hopefully ive solved my issue.
The heater has mostly not being working on the left recently so i decided i had to get this issue resolved. Ran Vag.com output tests on the V158 (left hand side temperature mixing flap) to see what was going on.
The values were fluctuating around all over the place so i did a reset on the basic values for open and shut. This temporarily worked for about 5 mins then it was back again. OK time for a new motor (apparently its not the motor that dies but the controller inside.) An updgraded version appeared in March 2005 and the new versions appear in 06 plates onwards (some 55's)
The motor part number is 7l0907511ak and cost me ?67.93 inc vat.
A quick list of what is required:
1, Put Aircon control unit into Service Setting
2, Remove Radio, Control Switches + Aircon Control Unit
3, Remove Dash end panels + Footwell covers + Wood trims
4, Remove lower dash
Once i had the lower dash removed i fired up the aircon to see the flaps in action. The V158 motor was constantly twitching which was causing the hamster noise behind my dash. All changed now I have heat on both sides and no hamster
lets hope it lasts.