Tempermental compressor on 87 SDL

The AC compressor on my 87 SDL is sometimes tempermental about coming on. There is no pattern to this, ususally we can shut the car off and restart and the compressor will come on and be fine for several days. On occasion the compressor will stop after operating a short while. This is very rare but can occur. At times the compresor will go several weeks without a problem. The climate control operates wery well and seems unaware that the compressor is not operating, except that the blower goes to high and the car gets hot inside. Acts like like a bad relay or something. Any advice will be greately appreciated.