First, check for combustion gases in the coolant which will tell you if you have a head gasket problem. There are a number of ways to do that. Do an internet search for your options.

Second, the fan has two speeds and it is very common for the low speed to go out. I have changed a bunch of them. In fact, it is common enough, that it would be a good idea to go ahead and change it.

And it is the fan motor itself that fails and only on the low speed. Not the relays. So, the fan assembly must be replaced.

It is possible now that the PT will have both problems. The fan problem leads to overhead problems, which kills the head gasket. As with many iron block, aluminum head engines, the PT's 2.4 is not tolerant of overheating.