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dliff 11-29-2012 03:44 PM

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.

woodenbmw 11-29-2012 03:58 PM

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.

downhiller 11-29-2012 07:42 PM

Quote:

Originally Posted by woodenbmw (Post 7221928)
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.

BMWFatherFigure 11-29-2012 11:25 PM

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.

woodenbmw 11-30-2012 06:24 AM

Quote:

Originally Posted by downhiller (Post 7222368)
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 ?

hornhospital 11-30-2012 08:06 AM

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.

woodenbmw 11-30-2012 08:28 AM

Quote:

Originally Posted by hornhospital (Post 7223051)
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

dliff 12-03-2012 11:56 AM

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


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