Temp Too Low???

If you installed a sensor into the WP, you must have drilled and tapped a hole for it, as the stock WPs have no such port.That then begs the question, is the sensor element even in the coolant flow?, or stuck in a stagnant pocket?, perhaps measuring the temp of the WP body, and not the temp of the coolant at all?

Look, I'm not trying to be a dick,to you. I'm just pointing out that the factory engineers probably thought of almost everything. When you try to out-think them, you need to have a good reason for ignoring the things they already thought of. If you supplement the factory gauge, you need to supplant it and either abandon the factory one or re-engineer,it, not the new one that you are going to trust your engine to.

Now, as an aside, I re-engineered my cooling system to take care of my engine. Automatically. I trust it to do it's job. Automatically.
I run NO aftermarket gauge. And you know how slow the factory gauge is.
As far as I care,the gauge might as well not be there,cuz I almost never look at it.
Besides, by the time I might notice an overheat, the gauge wouldn't be telling me anything that I don't already know.
If anything, the factory should have installed a missing belt sensor. I bet that wouldda saved a lot of engines. That might give you a few minutes of early warning that an overheat is pending.
For guys in hotter climes,with bigger engines,that get stuck in freeway traffic, I can see the value in a gauge.
As for me, my system takes care of that too, automatically.When the 7 blade'r kicks in,it roars; and then I am a happy camper. And the best part is it usually roars after,not-during, the run; to be ready for the next one.As long as I hear the roar, I know the belt is still on there!