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Thread: Fan runs...but does not turn on when AC is turned on

  1. #1
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    Fan runs...but does not turn on when AC is turned on

    So my 2003 2.5l was running well all summer. Then I lost AC all of a sudden. My fan kicks on various speeds as engine heats up but does not come on like other threads suggest when AC is turned on. Also, AC blows hot now too. AC compressor clutch is working and compressor is spinning . However it does not cycle on and off like it should. Could this be the ac pressure sensor?

    Would pressure sensor issue allow the fan to operate normally with engine temps but not get triggered by ac turned on?
    Last edited by JPele21; 10-21-2018 at 07:12 PM.

  2. #2
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    Anyone have any ideas. I am thinking of grabbing a set of gauges to check high and low pressures but I’m not convinced there is a leak.

  3. #3
    Join Date
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    It could be anything! I would expect more productive response if I perform the basic research and testing first (refrigerant pressure, power supply/fuses check, error code scan.. etc.) and share the findings on here. I would also provide more specific info about the vehicle including specific engine model, any prior related malfunctions and repair. Here are few good places to start:
    https://www.newtis.info/tisv2/a/en/e...check/GbGkqA9N

    https://www.newtis.info/tisv2/a/en/e...-lines/PkzYPoi

    https://www.newtis.info/tisv2/a/en/e...ing-functions/

    Good luck!
    Last edited by tekoo; 10-29-2018 at 12:38 AM.

  4. #4
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    Thank you for resources. Will work on some more trouble shooting.


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  5. #5
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    My pleasure, happy to help. Keep us posted on the progress!

  6. #6
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    Team,

    I’m having the same issue I have had for over a year and before I run it down to the local bmw specialist I wanted to ask if anyone knows if there is a specific combo or sensor/switch that turns on the cooling fan when the a/c is turned on? I know the computer looks for 7 or so different readings to control fan output.

    I have 2003 2.5i, manual

    -Ac blows hot air
    - compressor is engaged and spinning.
    - local shop evacuated/recharged and added dye
    -Cooling fan comes on when temp needle is in middle of the temp gauge. Turns off, etc
    -Fan does not come on when ac switch in cabin is turned on and compressor is engaged
    -cooler sensors replaced
    -replaced cooling fan with new bmw genuine fan

    I did not replace the ac pressure sensor but not sure if there is an easy way to test it yet(tonight’s reading)

    Thoughts?





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  7. #7
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    Well I got dye put in my ac system and I looked around with a black light and I see no noticeable leak in the engine bay.

    That said I did notice today that my fan was responding to me turning on the ac and off the ac. It was only spinning at about 20% power from what I could tell. Then after the car ran in my parking lot for about 10 minutes it would no longer cycle with the ac on and off switch it just stayed off until engine temp got too high.

    No cool air during about a 15-20 minute run of the car with ac on




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  8. #8
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    Today semi cool air for first 10 minutes of drive at 80 then non. Fan running partial speed


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  9. #9
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    Did you replace the temperature sensor on the lower radiator hose leading from radiator to engine block.




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  10. #10
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    Last fall I did replace the sensor before replacing the fan. I figured the sensors were the easiest fix before replacing a $600 fan


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  11. #11
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    Lost the ability to get fan to turn on and off with ac butting pushed. It worked twice but then didn’t no matter what combination of the controls I turned on.


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  12. #12
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    From what you just said... replaced the sensors and it got worse... perhaps one of the new sensors is bad. Just my take on your description on the outcome of replacing the sensors.

    Were the replacements OEM or better .... there are a lot of cheap/counterfeit parts floating around.

    Plus use electrical contact cleaner on connections to make sure you have solid electrical connections.


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  13. #13
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    Oem from ets


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  14. #14
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    I’d swap out the new with the old ones...one at a time to see if one of the new sensors was bad. 50/50 chance with the old ones being bad as well... but might be lucky and diagnose an issue with a sensor.


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  15. #15
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    I’m gonna try it and if not the backup plan is the local bmw specialist. Will let you guys know
    How it goes


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  16. #16
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    ON THESE ENGINES...

    The fan will NOT always be on with A/C!!!

    That ONLY applies to the older engines

    M54 (what your car has) and newer use a PWM controlled fan. This means it can control the speeds much more gradually, it also means the fan will NOT kick on unless it needs to. The fan will NOT always be on when A/C is on. Most of the time yes but you can not use that alone as diagnostics.

    Going into my TENTH YEAR of providing high quality reproduction BMW fabrics!

    PRICE CUT on ALL FABRICS
    Offering the best prices on the best quality reproduction fabrics!

  17. #17
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    Thanks that is the first person to clarify that. I saw a lot of other posts that indicate the computer and sensor controls but didn’t realize that ac button and compressor engage does not necessarily equate to fan running.

    Thank you.


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  18. #18
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    Diagnostics came back from the local non dealer bmw specialist. Looks like ac compressor going bad. Jacked up pressures that are in turn also likely attributing to the inconsistent fan speeds and engagement.

    Quote was a bit high but working on the negotiation where I can.

    Glad it was a little beyond my capes working a 60-80 hour work week. Just not enough time to focus on car troubleshooting beyond some of the simple sensors etc. fingers crossed we are back in business soon




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  19. #19
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    New compressor and dryer. Ac cold again. Fan spinning full speed and cycling.


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