Sounds like you have an issue with circulation. The water pump could in fact be the problem too. If that thing is caked up w/crap from sitting then it is definitely going to have issues w/fluid passage. As far as the thermostat is concerned, I am sure most of us here run OEM, cause the thermo is one of those parts like a PCV valve, it's best to run OEM or it might whistle at you. For the switch? Hmmm, I would say check the fan relay under the hood before installing any auxillary switches. This is usually the main culprit. Good luck!!!