1993 Ford Escort AC compressor causes car to stall

I had a friend rig up my AC compressor to the battery, but now when I get to a stop light, the car vibrates like crazy and stalls it out. The AC hasn't worked in years. It worked fine like 5 years ago. Now, the AC works, but I have this problem. There is a funny switch on the left side, that a previous owner put to turn on the compressor. The regular button on the dashboard does not turn it on. I brought it to some people, and they said, it's not wired through the computer, so the computer can not tell the engine to idle higher, and that's why it stalls. So, we thought it might be the AC switch. I got a part, but it's the wrong one, and what I think we need is the blower motor switch. But the thing is, it blows air just fine, it just doesn't turn on the compressor. So could the part be partially defective or something? I'm debating whether to replace this part or have someone wire it up differently. If I'm to replace the part, I have to find it, which is rather hard. What do you think?

Dustin
ShrewdSpirit@hotmail. Com