Just paid $1200 to have my van worked on (a/c fixed, fuel tank resealed,� gearshift linkage, oil change, emissions). Mechanic said fan should be on high-speed whenever a/c is on, is this true? 
Now I notice a really bad vibration (can feel it thru pedals) when a/c fan is on high. 
Could this vibration have to do with fuel tank being dropped and re-installed?
I dont know if fan was ever on high before but I never noticed this vibration back when the a/c worked before (10 years ago).
Also van now has no pick-up whatsoever, I press the gas pedal and it takes forever for me to take off.
Regarding a/c all mechanic did was fill it with freon R12 (3 1/2 pounds cost $262.50).
It was $400 in labor to do the gas tank with me supplying the kit of parts.
The oil change cost me $106.50 because the drain plug stripped and labor to install a helicoil was $80.
I have to take van back on Tuesday for them to check if any of the valuable freon has leaked out.
Its so frustrating that whenever I take my van in to be worked on., it always comes back with the original problem fixed but with a new set of problems appearing!

-David (1987 Wolfsburg)