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For some reason the temp gauge on my '98 Integra won't move past the halfway mark. It seems to just sit there at about 3/7 of the way across (just before halfway) no matter how hot it gets. I figure it is much hotter than what it is telling me because the other day the needle was where it always is but when we plugged in an OBDII scanner it said ~220F.

The car seems to have overheating problems, but I need to have an accurate temp reading before I can figure out under what conditions it overheats so that I can then, hopefully, find out what's causing the heating issue. Already replaced the thermostat with a 170F model and put in an aluminum radiator.

Could the gauge itself be defective? Since the OBDII reading was much higher, and the car exhibits overheating symptoms at times, wouldn't that suggest the sensor itself is still good?

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Or maybe it is a bad sensor and the OBGII reading was wrong and the dash gauge is correct?

The reason I assumed it is overheating is because of the overheating symptoms I get when I run it in the heat (85-100F weather) or with the AC on. It starts to run really crappy - the engine bogs down, some sputtering. Could this be the result of the stock computer trying to adjust for high temp readings from a faulty sensor?

The AC also stops blowing cold eventually. I am guessing the stock computer cuts out the compressor when the sensor reaches a certain temp.

If my assumptions are plausible, I guess I need to find another way to check the coolant temp to see which one is accurate - the dash gauge or the sensor.

vtaker

the scanner is probably correct. theres three temp sensors:

1.one for the ECU under the dist on the head
2.fan switch on thermostat housing
3.sending unit for gauge right next to ECU sensor (one wire yellow/blk i think)

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Yeah, it probably is.

My neighbor has a thermometer gun and we shot it at the inside wall (facing the motor) of the radiator. The passenger side read 180F. It seems around 195F the fan would kick on, and then go back off around 180F. When we shot the driver side of the radiator it said 215F, and the temp never really fluctuated significantly. This is while the car idled with the AC on.

There are two fans, one on each side, and it looks like the one on the driver side isn't coming on at all. The 180F side fan is located on the side of the radiator facing the motor, and the fan on the 215F side is on the opposite side. When we put our hand behind the radiator where the 215F side fan is located, we felt no air going in our out so it looks like that fan isn't coming on at all.

Anyone have any tips to diagnose why the fan isn't coming on? Are both fans triggered by the same switch?