Steady Temp Gauge?

[Piperbill]

My Z3 1.9 Roadster's temp gauge fluctuates between 1/4 and 1/2. It never seems to go past halfway, although I haven't driven it in our hot summer yet. My Coupe, and my other older BMW gauges always hit the midpoint and stayed there consistently. Should the 1.9 version gauge be just like any other and hit the midway mark, or is some fluctuation normal on this series?

[328 Power 04]

Your thermostat is likely stuck open.

[catimann]

I think it should act the same as your other car and probably every other car I have ever had. That said it could be all sorts for stuff causing the problem. The more problems I figure out the more I find the causes can be pretty strange. If you replace the thermostat and as part of that replacement you have to disconnect and reconnect the wire to the water temp sensor then what is to say it was not a bad electrical connection in the first place?
Electrical problems can come from very strange places and often are bad grounds. I had an issue with one car where I cleaned the grounds in many areas but never thought it could be a bad positive connection. Since your electric temp gauge is doing strange things try the connections first, even the fuses.

[Vintage42]

My Z3 1.9 Roadster's temp gauge fluctuates between 1/4 and 1/2. It never seems to go past halfway...

All the needle gauges are the same. They don't indicate temperature, but stay vertically motionless from 170 to somewhere over 225. Your thermostat is bad, not even holding 170.
I installed a digital gauge to watch the temperature. My original thermostat allowed the coolant to fluctuate between 170 and 195, depending on driving conditions. A new thermostat holds a steady 206 under all conditions.

[Piperbill]

I’ve only had this one for a few months. The gauge doesn’t fluctuate wildly, just doesn’t stay midway like the other BMWs I have (or had). The needle warms to 1/4 and then kind of moves towards the middle and hovers around the 3/8 mark or so. Doesn’t seem hot but the weather has been cool, so hard to tell. I’ll check the thermostat and connection this week. Thanks for the suggestions!


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[me77]

Your thermostat is likely stuck open.

+1

[BimmerBreaker]

Electrical connections can be tested - the fact that the sensor is reading anything (varying from hot to cold) and tending towards cold after running indicates the thermostat is faulty.