a/c trouble in 97 civic

Hello all, I have a 97 civic EX and last month my A/C went out when I was driving. I checked both the fuses inside the car, and under the hood and that checks
out. My step-father was up over the weekend and he hooked a wire directly from the battery into the A/C compressor, and the A/C started working in the car. We tried making a temporary fix by putting alligator clips at the end of the wire and having me just attach before I drove the car, but we soon found out a couple days later that this caused the A/C to build up too much pressure, and it would start to make a whining noise when I was driving around. I have since stopped using the wire method. Since the A/C works when direct power is applied to the compressor, do I need to buy some type of relay? If so, what is the specific name of the part, and is it fairly easy to change? Thanks.
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