The A/C compressor's drive belt should be well tensioned - about like
the belt to the power steering pump.
One needs to loosen the bolts (probably three) that attach the
compressor to its bracket but NOT the bolt that secures the pipes to the
My '80 has a tensioning screw with a small hex nut for a wrench, your
car may differ. Start turning it while watching the belt so it is
tensioned not made looser. I have to access the mounting bolts from
underneath but the tensioner from the top.
When you're satisfied with the belt's tension - and don't be shy about
tensioning it, the spec. is 1/4" deflection with a 13 lb push - tighten
the compressor's mounting bolts (to about 40 ft lbs.)
Be sure to note how many mounting bolts get loosened so the same number