Re: Coolant temp senser
Difference in sensors (T-head vs. the Pin or Spade connector) is that a gauge sensor has a gel inside of it that changes resistance with heat allowing the needle to move as temp rises and resistance drops. The other uses mercury or similar fluid to expand as it gets hot pushing on a plunger inside the sensor, against a spring, until it contacts the lip inside the sensor bore grounding the sensor to trip the light on the dash.
One is either on or off, the other offers an analog resistance to ground proportional with temperature. I imagine the gauge sensor would eventually allow the idiot light to come on but I have no ideas as to at what temp that would occur. It also costs a lot more than the more complex to make and complicated idiot light sensor, which shows you how people that have expensive toys will pay more to maintain them (both Cadillac and Chevy use the same parts, but it cost a lot more to buy the Caddy part than the same part from Chevy). This is because the Caddy owners knows that deep down inside that "Best of all it's a Cadillac" (a marketing ploy dreamed up to sell Chevy Novas to Cadillac owners at a higher price).