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So last year, after 6-7 months of owning the car, I finally discovered the secret menu. Flipped to channel 7 and lo and behold, I'm reaching 74-75F and never get to the magical 79F. So I search, realize my t-stat is bad and decide to replace it. Job is pretty easy, I replace the metal ring, new behr tstat, etc. Car is reaching 81-82 now and I forget about it for a while. Fast forward to last week. Temps drop suddenly and we're seeing 32-37F daytime averages now so fall season is definitely over. Out of curiosity, i go into the secret menu and flip back to channel 7 - I'm dismayed to see 75F under highway cruising. In heavy traffic, it reaches 77-78 but as soon as speeds pick up, it never gets above 76. So is my t-stat bad...again?? In a year? I never did replace the temperature sensor on the top of the tstat housing - maybe that's the culprit? Thoughts? Dammit, tell me these things last more than a year. :eek7:
 

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I see you did not replace temp sensors on top along with the t-stat. You prob didn't do the 2nd sensor either.. I was still having issues with mine after doing t-stat until i replaced both sensors.. the sensors were not expensive. 1 sits on top of t-stat and 2nd near radiator passenger side.. 2nd one by radiator was a PIA..
 

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IIRC only one feeds the cluster and the other runs the aux fan - can't remember which is which but there's a thread out here that covers it.
 

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Replace the temp sensor/switch located on the t-stat housing.
 

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Replace the temp sensor/switch located on the t-stat housing.
...which is the one for the DME/cluster input. The one on the hose is for the aux fan.
 

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Do our AUX fans have resistors on them that go bad over time like is common on the E30's? Cause I think my AUX fan isn't working..
 

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Aux fan operation

Do our AUX fans have resistors on them that go bad over time like is common on the E30's?
Cause I think my AUX fan isn't working..
With A/C on, the auxiliary should be running. Speed of the fan is controlled by the DME, through the input from the
sensor located in the lower radiator hose (radiator outlet).

With A/C off and the radiator outlet temps become too high, the DME will turn on the fan.

Regards,
Alan
 

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^^^ Fan will not necessarily be on with A/C compressor operation, but should come on within a minute or so.

...which is the one for the DME/cluster input. The one on the hose is for the aux fan.
Yep.
 
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