Installing 195 Degree Thermostat

[NotEnoughGPs]

2002 Pontiac Grand Prix 40th Anniv GT, 227,000 miles. I have been running the 180 degree thermostat. Upon replacing the radiator hoses, I decided to reinstall the original oem 195 degree thermostat.
Now, the temperature gauge rises to a high temp of only 170 degrees or so. I removed the 195 degree thermostat and dunked it in boiling water, and it opens, then closes when removed from the water. So, I am convinced it is ok.
For now, I installed the 180 degree thermostat again, and all is well. The temperature gauge rises past 180 degrees and then settles back to where it always did before, and the heater throws much more heat.
I don't believe that there is anything wrong with the operation of the temperature gauge or the coolant temperature sensor.
Also, with the 195 thermostat in place, and the car idling in a warm garage, the temperature gauge still is not rising.
The PCM was programmed by ZZP, and the fans stay turned on after the engine is shut down. With the 195 thermostat installed, I regularly checking to see if the fans are running non-stop, and they are not.
I can't figure why this is happening. Upon searching on here for "thermostats", "temperature gauge", "coolant temperature sensor", etc, there is a claim that the operation of the cooling fans is the same with a 180 or 195 degree thermostat since difference is only 15 degrees.
I want to run the 195 degree stat to get more heat in the interior of the car.
What are other things I could look at?

 

[Fivefingerdeathpunch]

It's possible that your 195º thermostat opens before 195 and thats why it ran cooler. A better test is to place it in water and see the point at which it opens and temp the water with a temp gun to see exactly what it was.

Or just spend the 5-10 bucks and buy another 195º and toss it in the car and see what happens.

Only if the fans where programmed for the 180 would they kick on just past 180-185ish, otherwise on the open road you'll see 175-180. And if they were not programmed the temps would still rise to 195+ in park because nothing is stopping it.

 

[blueguy]

The difference in operating temp is based on the rating of the t-stat + 10-15*.

My 160*'s always ran around 175~ based on my Aeroforce readings and a new temp sensor.

180*'s normally sat around stock rated temp...but my 195*'s would see nearly 200*, easy.

I'd venture to say you should just install a new 180* and have the system totally flushed and gone through if you haven't done that yet.

 

[NotEnoughGPs]

It's possible that your 195º thermostat opens before 195 and thats why it ran cooler. A better test is to place it in water and see the point at which it opens and temp the water with a temp gun to see exactly what it was.
Or just spend the 5-10 bucks and buy another 195º and toss it in the car and see what happens.
Only if the fans where programmed for the 180 would they kick on just past 180-185ish, otherwise on the open road you'll see 175-180. And if they were not programmed the temps would still rise to 195+ in park because nothing is stopping it.

I am going to try a new 195° thermostat rather than mess around with the old one, which is 14 years old. It's just funny how the old stat worked fine before I removed it.
As for the temp that the fans turn on, I do not think ZZP did anything to the PCM to make them turn on at 180°. They did not know that I was going to install the 180° thermostat.
Question: Can the fan turn on temps be checked with HP Tuners?

 

[Fivefingerdeathpunch]

Yeah, you could read the file from the car and it would tell you on and off temps.

 

[NotEnoughGPs]

The difference in operating temp is based on the rating of the t-stat + 10-15*.
My 160*'s always ran around 175~ based on my Aeroforce readings and a new temp sensor.
180*'s normally sat around stock rated temp...but my 195*'s would see nearly 200*, easy.
I'd venture to say you should just install a new 180* and have the system totally flushed and gone through if you haven't done that yet.

I am going to hook up an Aeroforce to see what coolant temperatures I am getting.
I have some high miles on this GP GT, there are no go fast mods on it. I just want to get as much heat inside the car as I can, so that's why I decided to go back to the 195° thermostat. I did not drive this car much in the wintertime in past years. After driving in single digit temps the past few weeks, the interior temps are not that comfy. I have to keep the fan on 3 or 4 setting to keep the windows clear from frost.
I also have flushed out the cooling system, and installed new radiator hoses. It is going to eventually need a LIM gasket on down the road, and when I install one of those, I will replace the coolant.
Also, there are many other 3800 owners who claim that there is no need to go with a 180° stat, as there is nothing to be gained. The may be a gain in fuel mileage by going with the stock 195° thermostat according to many.
I just did not expect to encounter a problem by reinstalling the 195° thermostat, and I want to figure out why.
Thanks for responding.