01'GTI VR6 GLX A/C Problem

[rictavusa]

Just bought a 01'GTI GLX VR6 with 52K miles and equipped w/ CLIMATRONIC A/C system.
Before buying it I test drove 2 times and the a/c was great, on the next day, driving it on normal day cruising around I noticed the temperature inside was going up when I was in the traffic (city driving & seating at light). Outside was around 92F. and the a/c stopped. I stopped at gas station and found that the a/c compressor wasn't turning. On the next day I tried again and it worked fine for 10-15 minutes and stopped again. Took it to a mechanic that I know for years, after hooking up a pressure gauges he found that the high side pressure was going above the specifications and the radiator fans wasn't kicking in the way they are supposed to do when the pressure goes high. On a highway driving the a/c works fine (wind cools down the a/c condenser). The mechanic is suspecting that the a/c high pressure switch is the cause of that problem... any one can help me on this before I buy unnecessary parts and go for an "elimination" type of repair??? I don't have an extra money right now to be guessing and buying parts + paying labor for the right repair.
Please help me... I'm melting...

[veedubmechanic]

sounds like the h-block on the firewall is bad. 75% of the ac probs i see are related to that being stuck. Or the system is overcharged wayyy to much.