Engine Coolant Temp difference


Active Member
Mar 20, 2017
I have a 93 gt 5 speed with a on3 kit and it’s controlled by a Microsquirt. I have an auto meter coolant temp gauge In the factory gauge sensor spot and at normal driving that reads between 220-215. I removed my heater core tube and used the hole that the pipe threads into the lower intake manifold with an adapter for the ecu temp sensor. That reads around 180 driving consistently according to tunerstudio software . I have a 180 thermostat, and I used an ir gun to check temps and they read closer to the 180 mark ( t stat housing , upper rad hose, anfitting on that connects my upper rad hose). I also have a derale pwm fan controller that seems to be set to turn the fan on at 180ish which seems right due to the ect temp staying around that temp. I have a duel path afco radiator

I’m not to sure which temp to go by, I removed the auto meter temp sensor and tested it in a glass of water and it’s correct. I am only running an alt, wp, crank and there isn’t much belt on the water pump ( fixing that with a bracket and tensioner for driver side ). Could that make a change in temp by not spinning the waterpump fast enough? If not any ideas on how to get the accurate temp of the coolant ?
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