Climatronic Error 214: Troubleshooting Guide

Hello,

I have a Golf IV, manufactured in 2000, with 90 horsepower, and AGR (adjustable head restraints). Recently, the Climatronic system has been displaying the error code 'hex214,' which, according to the error code description, indicates 'supply voltage (0x6 0x7).'
Can someone give me a hint about what this means and where the cause of it might be?
Sure, here's the translation:

'Thank you in advance.'
H.

Connect a proper diagnostic system and read the fault memory of ALL systems correctly, then we can say something about the error. Your error code is incomplete; it's missing the error type (is the supply voltage too low or too high?). Furthermore, in this case, the other systems are particularly interesting, because only then can you decide whether to start with, for example, the alternator or the climate control system itself.

Key diagnostics sucks...