Air Conditioning ?

Remove the connector from the clutch cycling switch on the accumulator(big metal can). Short the connector with a paper clip or whatever and then turn on the A/C. While you're doing that, check your freon charge. It should be around 30-50 PSI. If it's more than that, shut it off! That means you've got something blocking the line. If it's too low, add more freon, and see what happens. If it doesn't leak out, you're good.

You can get it filled with R-12, but for the price you might as well buy a brand-new system!
They can vacuum it out and fill it with R-134 for much less, just have to change out the accumulator and orifice tube.

More likely, you've got a block in the line. I would change the accumulator, front orifice tube, and rear expansion valve, and have everything flushed out, then refilled. I give good odds that the front orifice tube probably looks like a cat turd right now.