Coolant temperature

Noticed my coolant temperature gauge doesn't work on my new 325e. Is there an 'idiot' light that will turn on if it overheats, or will I be completely oblivious if it does? It runs excellently, but that's not the best indicator of engine temperature.

Is there a way to test the gauge before replacing the sensor?

I am planning on getting a Bentley but I need to drive around (to work mostly) and I'm not sure where the coolant temperature sensor even is.

edit:
Oh, and does the fan clutch work off of a different sensor? On my VW it has a separate one so even if the gauge sensor fails it will still turn the fan on. If the sensor is bad and it's the only sensor it's possible the fan will never go on, which obviously is bad.

Thanks.

I don't know about testing the gauge sensor, on my 87 325e however, the fan operates from two sensors located on the radiator. One for low speed, the other for the high speed fan. You can test them by jumping the terminals together. If the fan comes on, replace the sensor. I hope this helps.

Originally Posted by woodenbmw

I don't know about testing the gauge sensor, on my 87 325e however, the fan operates from two sensors located on the radiator. One for low speed, the other for the high speed fan. You can test them by jumping the terminals together. If the fan comes on, replace the sensor. I hope this helps.

this /\/\ is the aux fan mainly used when running ac. the fan clutch is oil operated. the hotter the oil within the fan clutch, the more it engages and "locks". if it is good, after you shut off the engine after running it for a bit, you should have good resistance. if it is bad it will spin somewhat freely. or you can do the newspaper test.

Quick test for gauge function - earth (ground) the sensor wire with the ignition on, engine not running. have someone watch the gauge. It should climb RAPIDLY. If it does the gauge and wiring are good. Change sensor. If not gauge or wiring faulty. Don't leave the wire grounded for more than about 5 seconds - just long enough to see the needle get to about 3/4 scale. There is an overheat light in the red end of the dial face - similar to the low fuel light in the fuel dial face.

Originally Posted by downhiller

this /\/\ is the aux fan mainly used when running ac.

If we are talking about the same fan, could you explain why my fan turns on in the middle of winter when I'm running my heater ?

If you have it on defrost, it actually cycles the A/C, even though the heat is on, and running the A/C runs the auxiliary fan.

Originally Posted by hornhospital

If you have it on defrost, it actually cycles the A/C, even though the heat is on, and running the A/C runs the auxiliary fan.

That makes sense, thank you for the info

Thank you for the replies. I'll test it out soon.