temp gauge showing cold

[brian_s]

The water temp gauge on my 1991 525i/A (215,354 miles) is showing colder than normal. It normally indicates a dead center reading. It is now on the hash mark just left of center. About 9000 miles ago I replaced the thermostat/water pump/fan/fan clutch/belts/fan shroud. It just started doing this yesterday. I drive 28 miles (40 minute drive) one way to work and it is usually in the 80's outside during my morning drive. The temp should be well above that. Is it a faulty gauge or sensor? Thanks in advance for the advice.

[MicahO]

If the gauge makes no movement at all, I'd suspect the gauge or the temperature sender/wiring for same. If you are getting slight movements on the temp gauge, I'd suspect that the thermostat is stuck open.

See if the temp comes up (even just a bit) while the motor sits idling, with no airflow through the radiator. If yes - get a new Tstat.....