Originally Posted by
llaprad1 
The OEM gauge has 3 "settings" Cold, operating temp, and hot.
Cold is 0 deg and something like 150 deg.
Operating temp is (150 deg) to 212 deg.
Hot is over 212 deg.
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If your engine is 170 deg. your needle will read exactly in the middle.
If your engine is 200 deg. your needle will read exactly in the middle.
If your engine is 185 deg. your needle will read exactly in the middle.
It may not look exactly in the middle, but it's in the same exactly spot close to the middle if everything is working as supposed to.
If your engine is 0 deg. the needle will be all the way to the left.
If your engine is 120 deg. the needle will be all the way to the left.
If your engine is 50 deg. the needle will be all the way to the left.
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If your engine is 190 deg. your needle will not be "a little over the middle." It will be in the gauge's normal middle (which may be a little below the hash mark).
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Furthermore, your needle does not start moving upward until the moment you hit 213 deg.
The only way to see this and have it make sense is to hook up something that sees actual engine temperature, not engine temp status. Like an OBD2 scanner or an Informeter or a Scan gauge.
Sorry, but I replaced my dash cluster today and had a chance to test this. Long story short, it's not true. At least on my B14. Using resistors, I hooked a different resistance to the signal wire and the gauge read different degrees relative to normal operating temp. B13's should react the same, as it's the same system used for the dash gauge reading.
What this means is that as your temperature slowly climbs to operating temp, your resistance through the thermistor will slowly fall, and your gauge will appropriately slowly go up. If you stop shy of operating temp, the gauge will show as such; slightly below normal.
This "3 position" theory doesn't make sense, considering the coil that drives the gauge is directly resistance-dependent, and the sensor (thermistor) has fully-variable output in relation to temperature.
Your gauge will display the relative temperature location, no matter what temperature it is . The big thing, though, is knowing where "normal operating temp" is on your gauge, as they can be messed with or have other affecting variables on it.
tl;dr: Gauges react directly to resistance.
If your gauge looks low, there are 2 possibilities: 1 - Your temperature is being maintained just shy of operating temp, or 2 - Your gauge's location for normal temp is simply low . An accurate reading of your coolant temp will tell you which it is.
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