I have the same problem. We put in the same pads that we did last year and it worked great. But now, What the heck?
I already know now what is wrong. If the humidity is high outside, the swamp cooler cannot cool well. Also the sun has to beat on the sides to help the water in the pads evaporate. It is never humid here which is why they always worked before. But now, weirdly, its a sauna outdoors. Hot and humid so the swamp cooler is not blowing cold air. This off the wall humid heat is the only difference that could be affecting my swamp cooler.