2004 chevy venture fans would not turn on, and it starts to overheat

I see the question was posted Aug 24, 2008 so likely the originally poster of the question will never see what I'm typing here, but others who are searching for info will see it.

I'm wondering what was meant by "starting to overheat"? Does this mean that the temperature needle is going past the center of the gauge, higher than normal? And then when the air conditioner is tunred on and the fans come on, does the temperature regulate so that the temperature needle stays at lower than half way on the temperature gauge? If this is what's meant by "starting to overheat", then my chevy venture has the same problem. I've spent many many hours already searching for an answer and I've come up with my own theory on this. To make this clear, this isn't a solution to the problem, but it's more of an idea that I'd like to see some feedback on from those who have the same vehicle and symptoms, and from those with mechanical experience.

My theory is that the programming in the GM 3.4L PCM sets the turn on temperature too high for the engine to cool properly. The thermostat is rated at 195 deg F, so the operating temperature shouldn't be much higher than 195 deg F. As far as I know, GM doesn't give a specification for the turn on temperature of the fans, but I've read from one source that low speed fan turn on is 208, high speed fan turn on is 230, and fan turn off is 203. When the gauge needle is pointing straight up (half way), the the temperature is about 212 deg F. When the air conditioning is turned on, both fans turn on at high speed. When the fans are in low speed, both fans turn on with low speed, but it's not enough to stop the temperature from getting higher, so to get both fans running at high speed, the temperature has to climb up to 230 deg F before the high speed kicks in and then it takes time for the temperature to drop down to the turn off temp about 203 deg before it begins its climb back up again. At about 225 deg, my transmission starts to act up by having jerky shifts from the excess heat, especially on uphill.

In the winter time, the engine coolant temperature on my van regulates very well constantly between 195 and 200 deg F. In the summer time, with the air conditioner on, it also regulates very well constantly between 195 and 200. But in the summer time, with the air conditioner off, it goes to the higher temperature. What would be wrong with the temperature regulating between 195 and 200 with the air conditioning off? By my logic, there''d be nothing wrong with it. I think this could be another design flaw by GM that they dare not admit too because it's all about money. Meanwhile, the professional mechanics likely won't consider that the GM may have programmed their fan turn on temperature wrong. They'll change the defective parts, charge the big bucks for their labor and move on to the next one.
I haven't read anywhere on the internet about this idea, so hopefully I'll be seeing some feedback soon. Maybe my idea is completely wrong. But maybe it's not.

Ed

Change the fans relay or ac\clutch relay