thank you!
i will do this regardless of my heat status.
the only reason i haven't been able to "use" the heat is because it blasts the exhaust into the cabin. So i leave it off.
I've used it, to test it basically, and it gets hot as hell eventually. But it takes a long time to get there. At least 15 minutes. So i will certainly look at the device and follow your instructions.
The temp gauge... well, it works well think. Yes it's gone a little above 80 during warmer weather. Usually these days it doesn't go above it though. But i've seen it go above it when the weather is more like 50-60F.

Story time.. In January, it was -10F for three days straight. Pipes nearly freezing in house, the whole works. And on the third morning, when i was taking the bridge across the hudson river and heading to a hardware store 10 minutes past the river's other side, i noticed the temp gauge was climbing. Now, i live about 1 mile from the bridge entrance, so seeing the temp climb by this point is a little startling. The bridge is 2 miles long, and by the time i got to the other end of the bridge, the temp gauge went into the red and just pinned up.
Needless to say i panicked, thinking **** i must have run out of oil fast or something and my engine is about to seize up. This was a horrifying feeling, and I'm on a bridge with heavy traffic. So i reach the end of the bridge and get on the first exit ramp which puts me at a diner. So i park the car, check the oil and it's totally fine. I hovered my hand above various spots in the engine and feel no heat. So i outright touch the engine and it's still ice cold. I touch various sections. There is no sign of warmth. It's -5F out at the moment so my willingness to keep my hands out of my gloves dissipates rapidly.
I go into the diner and fret over this, take a seat and have a coffee and do some research on the phone. I give up, and go back out, and decide to just start the damn car up and let it sit.
Sure enough, after like 2 minutes, the temp gauge slowly drops to the starting point of 40 C.
I pull away and go run my errands at the hardware store.

So, the temp gauge can go faulty in the cold!!!! But it's not "frozen", it's just downright messed up like the sensor is thrown off or something. Just documenting this in case nobody knew this!