During recent hot weather, my ac would occasionally run warm. I didn't check the compressor at the time because I was trying to get a hard starting problem fixed (it is fixed now). In checking the AC out a few days later, I found that the AC was cold but the compressor would run almost all the time when the AC switch was on. The AC condenser cooling fan never came on at any time. The condenser gets pretty hot since it sits next to the radiator. I used a pressure gauge set and the pressures seemed pretty high. The pressure was about 70 psi with engine off. With engine running, low P was about 55 and high P about 300. Since the electric condenser fan was off, I figured the temperature in the condenser was pretty high. Next morning with engine cold, the pressure with engine off was 55; with engine running low P was around 25-45, high P was about 135-170. The compressor ran a very long time (minutes) after the low P came down to the 25-30 range, and only stayed off a few seconds when it did go off. I let the engine warm and the condenser fan never came on. The fan does come on when I short the light green wire on the pressure switch to ground, and that seems to make the compressor cycle more. I swapped the condenser fan relay for the AC relay, and that also seemed to make the compressor cycle more often (on 30-50 secs, off 15 secs). So the AC seems to be working most of the time now, but the condenser fan never comes on. According to a data table I found for the triple pressure switch, it is supposed to turn on the fan when the "medium pressure side" of the switch sees pressures increasing to 164-206 psi. I'm not sure what "medium pressure" means here and don't know how to check the switch. I'm also not sure what is controlling the compressor cycle, unless it is the evaporator temperature sensor. If there are any AC gurus who could help out, I would appreciate it. This isn't an urgent issue with the cooler weather, but I would like to get it working right.