006 - connection to switchover block valve - this is the gizmo up behind the glove box with about a dozen vacuum lines connected to it - it controls the vacuum flow to all the duct damper actuators.

0074/75/82/83/86 - problems with the duovalve unit for the heater - up under the hood, driver's side on the fender behind the headlamp.

0102/103/106/107 - problems with the 2nd and 3rd stage fan activations.

Code 74 & 75 are the same problem, with 74 being a permanent failure and 75 intermittent. Same with 82 (perm) and 83 (int). 86 is a permanent failure.
Same deal with 102 (perm), 103 (int) for 2nd stage fan activation. 106 (perm) and 107 (int) is for 3rd stage fan activation.

Before I'd spend a single dime on parts, I'd check the A/C control unit in the dash. Contact the folks at Programa in FL (www.programainc.com), they may be able to test it for you for a small fee.

I replaced my duovalve unit (about $400 if I remember at wholesale prices) before having my control rebuilt, and I wonder to this day if that wasn't money wasted.

The controller will report all sorts of problems that it can cause on it's own. Possibly the 006 error is because it can't communicate with the switchover block valve, but that could be because the controller is toast in that area, or the block itself is bad.