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Thread: Air conditioning not working - BMW E46 M3

  1. #1
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    Air conditioning not working - BMW E46 M3

    Dear all


    Though I have been a visitor, I have only just registered, so would like to say hello, great forum, with great information.


    I have a 2001 M3 and when I bought it the AC wasn't working, and I assumed or hoped that it would be the fact it needed a gas, but alas after having the top up, it still wasn't working,


    I checked for error codes and not suer if there are related but have the following:


    28 AUC sensor - Open circuit / 30 AUC heating - Short circuit to ground.


    I believe this related to the AUC sensor of which I have ordered, but also have heard that this should not stop the AC working.


    The issue seems to be the AC compressor clutch is not engaging.


    I have checked the fuses, and all are good, I checked the pressure which is registering in INPA,


    so I assume the pressure switch is good, the heater buttons all registering as working when activating in INPA, and the temperature sensors internally and externally are registering.


    The only thing I have yet to check is the AC pump relay but I assumed if that were faulty it would throw an error code in INPA.


    Is there any one else that has had similar issues, and could point me in the right direction of what to test before dropping the car to the garage and having a big bill.


    Additionally, what is the option in INPA “disengage the AC clutch” do, is that designed to test the magnetic clutch mechanism.


    Many thanks in advance.

  2. #2
    dworthy's Avatar
    dworthy is offline Wagon meister :) BMW Tech Expert
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    Welcome to the Forum!

    The AUC will not keep the A/C from working, for all it does is check the Air Quality to see if the recircurlater needs to be engaged or not.

    What is the pressure you are seeing in INPA? Have you had the A/C system serviced at a garage yet?
    Darin
    Current:
    16 220i Active Tourer Platinsilver MET (C08)/Dakota Black (PDSW), P7ACA, P7LDA, P7LHA, P9BDA, 6sp Manual - Wife's new toy!
    05 325it Electric Red(438)/Gray(N6TT) ZCW, ZSP 5sp Manual Back set cover, trunk mat, Euro Infra-Rot front windshield, and mud flaps! Mr. Wagon My new Winter car.
    05 M3 Imolarot II(405)/Gray(N5TT) ZCW, ZPP 6sp Manual C.F. Lip, CSL diffuser, SSK, Euro Infra-Rot front windshield and a trunk liner! Mr. Go_Fast Stored for the Winter
    Past:
    95 318is Montreal Blue Met (297)/Beige(K1SN) RIP, killed by an Idiot.
    84 M535i gray market Burgandy Rot Met/Black Leather Lowered by Intrax on bilies, poly everywhere, B&B cat back system, K&N, and a hitch! Da Beast - Still running w/400k+!
    91 316i euro Tizianrot/Gray cloth - E-36 w/M-40 RIP, but great on gas! Best was 38 MPG
    82 528i euro Saphire Blue Met/Blue Leather RIP
    79 525 euro Green/Green RIP
    79 318 Silver/Black - The first one that got it all started
    M-Flight Member

  3. #3
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    Hi, thanks for the info, I didnt think it would stop the AC but best to check, and I think the issue with the error was acatually a loose connection, as after refitting it with a bit more purpose I was able to clear down the codes this evening.

    I had a mobile AC technicial come out and gas the system, it was holding presauure, but they drianed it and topped it up again.

    The pressure sensor is registering 5.7 Bar

    cheers

    John

  4. #4
    dworthy's Avatar
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    So I am not 100% sure where that pressure sensor is. If it's on the low side, that's way too high of pressure, but on the high side, that's way too low.

    What it should read, and this depends on the outside air temp, lower being cooler outside. Low side should be 30 psi to 50 psi, and the High side should be 150 psi to 200 psi.
    Darin
    Current:
    16 220i Active Tourer Platinsilver MET (C08)/Dakota Black (PDSW), P7ACA, P7LDA, P7LHA, P9BDA, 6sp Manual - Wife's new toy!
    05 325it Electric Red(438)/Gray(N6TT) ZCW, ZSP 5sp Manual Back set cover, trunk mat, Euro Infra-Rot front windshield, and mud flaps! Mr. Wagon My new Winter car.
    05 M3 Imolarot II(405)/Gray(N5TT) ZCW, ZPP 6sp Manual C.F. Lip, CSL diffuser, SSK, Euro Infra-Rot front windshield and a trunk liner! Mr. Go_Fast Stored for the Winter
    Past:
    95 318is Montreal Blue Met (297)/Beige(K1SN) RIP, killed by an Idiot.
    84 M535i gray market Burgandy Rot Met/Black Leather Lowered by Intrax on bilies, poly everywhere, B&B cat back system, K&N, and a hitch! Da Beast - Still running w/400k+!
    91 316i euro Tizianrot/Gray cloth - E-36 w/M-40 RIP, but great on gas! Best was 38 MPG
    82 528i euro Saphire Blue Met/Blue Leather RIP
    79 525 euro Green/Green RIP
    79 318 Silver/Black - The first one that got it all started
    M-Flight Member

  5. #5
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    HI thanks for the info.

    As the system is not running, I guess all ist measurimg is the presure in the system generally ? cheers.

  6. #6
    dworthy's Avatar
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    Okay, had to pull the diagrams out for this, wanted to know where that sensor was: https://www.realoem.com/bmw/enUS/sho...diagId=64_0770

    It's #13 and looks like that it's on the high side, so 5.7 bar or 90 PSI is way too low for the high side.

    I am assuming you know how each side works and how the refrigerant flows?
    Darin
    Current:
    16 220i Active Tourer Platinsilver MET (C08)/Dakota Black (PDSW), P7ACA, P7LDA, P7LHA, P9BDA, 6sp Manual - Wife's new toy!
    05 325it Electric Red(438)/Gray(N6TT) ZCW, ZSP 5sp Manual Back set cover, trunk mat, Euro Infra-Rot front windshield, and mud flaps! Mr. Wagon My new Winter car.
    05 M3 Imolarot II(405)/Gray(N5TT) ZCW, ZPP 6sp Manual C.F. Lip, CSL diffuser, SSK, Euro Infra-Rot front windshield and a trunk liner! Mr. Go_Fast Stored for the Winter
    Past:
    95 318is Montreal Blue Met (297)/Beige(K1SN) RIP, killed by an Idiot.
    84 M535i gray market Burgandy Rot Met/Black Leather Lowered by Intrax on bilies, poly everywhere, B&B cat back system, K&N, and a hitch! Da Beast - Still running w/400k+!
    91 316i euro Tizianrot/Gray cloth - E-36 w/M-40 RIP, but great on gas! Best was 38 MPG
    82 528i euro Saphire Blue Met/Blue Leather RIP
    79 525 euro Green/Green RIP
    79 318 Silver/Black - The first one that got it all started
    M-Flight Member

  7. #7
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    Hi, thanks for the posts.

    Yes know enough to understand the concept,

    I just went through each part, piece by piece, Checked all fuses. Checked the relays over the weekend, and they were all fine. Pressure, low to high was still reading the same for the pressure sensor.

    So started to remove trim under the bonnet with a view to checking the AC Compressor. Found initially that the AUX fan connector that I assumed was not connected to anything as it had no male counterpart, actually, did have a partner, that had been tucked right out of site, and only seen at a certain angle, in the good light of an August afternoon yesterday, I connected ti up, but alas still no AC compressor engagement.

    Then I was tracing the main wire to the AC Compressor, no visible, as I had removed the rad coupling, and got some good light, and sure enough, that too was tucked out of the way, under the AC pipes, hidden from initial view, but most importantly, it was NOT plugged into the compressor!

    So I popped the wire back in, fired up that AC, and boom, working Air ;0)

    It would transpire that when the car had its engine refitted nearly 12 months ago, the mechanics forgot to connect a few things up !! man do I feel lucky, as I was about to get the compressor checked and get the gas man back to depressurise the system ready to get parts replaced, and it was the most simple of fixes in the end.

    At least I understand the whole system now, and where all my additional relays are and how to get to them, so it was not a completely wasted exercise.

    Thanks to all who viewed the thread and offered advice.

  8. #8
    dworthy's Avatar
    dworthy is offline Wagon meister :) BMW Tech Expert
    Join Date
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    16 220i 05 325it 05 M3
    It's good that you found the problem, and yes mechanics do get in a rush and forget stuff. Even after wrenching for over 20 years on BMW's I still go back at the end of the job and double check my work. I would say about 95% of the time everything is good, but it's that 5% that gets you in trouble if you know what I mean.

    As long as you learned something, it's never a waste of time!
    Darin
    Current:
    16 220i Active Tourer Platinsilver MET (C08)/Dakota Black (PDSW), P7ACA, P7LDA, P7LHA, P9BDA, 6sp Manual - Wife's new toy!
    05 325it Electric Red(438)/Gray(N6TT) ZCW, ZSP 5sp Manual Back set cover, trunk mat, Euro Infra-Rot front windshield, and mud flaps! Mr. Wagon My new Winter car.
    05 M3 Imolarot II(405)/Gray(N5TT) ZCW, ZPP 6sp Manual C.F. Lip, CSL diffuser, SSK, Euro Infra-Rot front windshield and a trunk liner! Mr. Go_Fast Stored for the Winter
    Past:
    95 318is Montreal Blue Met (297)/Beige(K1SN) RIP, killed by an Idiot.
    84 M535i gray market Burgandy Rot Met/Black Leather Lowered by Intrax on bilies, poly everywhere, B&B cat back system, K&N, and a hitch! Da Beast - Still running w/400k+!
    91 316i euro Tizianrot/Gray cloth - E-36 w/M-40 RIP, but great on gas! Best was 38 MPG
    82 528i euro Saphire Blue Met/Blue Leather RIP
    79 525 euro Green/Green RIP
    79 318 Silver/Black - The first one that got it all started
    M-Flight Member

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