Okay so I have had this issue with my car since I bought it 2 years ago. The temp gauge in my car reads totally cold almost all the time, it will go up to about a quarter if I sit and idle for a long time, radiator fans will come on then it will drop to cold again very quickly. If I am driving no matter how hot it is out it always reads cold. The heat works takes a while to warm up but it does work, AC works as well. When I start the car it idles at 1500rpm after 10 minutes or so it will drop to 900-1000rpm and stay there. No check engine light, or any codes stored.

I was told by many people the thermostat was probably stuck open which didn't really make sense to me because I thought that would make the heat not work, but I replaced the thermostat anyways and the temp gauge still doesn't work. So now im thinking the coolant temp sensor might be issue, how likely is it for one of those to go bad? Could it be wiring and not the sensor itself? Anyway to test it with a multimeter? I'd really prefer to not keep throwing parts at it to see what sticks. I appreciate any help.

1994 Honda Prelude H23A1 all stock.