Results 1 to 24 of 24

Thread: AC lock sensor

  1. #1
    Join Date
    Dec 2014
    Location
    Los Angeles, California
    Posts
    144

    AC lock sensor

    After taking my 91 850i to two shops still no fix for my AC...I’ve been looking for information on how to modify the lock sensor to make new compressors work with the car but all the threads are old and the images/links no longer work. Does anyone have the information on how to modify the sensor? I also read if you buy the newer sensor it will work with new compressors is this the correct part number? 61358360039 I searched for one and it’s not available anywhere. The summer was almost unbearable driving in my 8er but now the weather is cooling down and I can actually drive with my windows up lol.

  2. #2
    Join Date
    Sep 2008
    Location
    Santa Barbara
    Posts
    3,462
    My Cars
    91 Dinan860 & 91 850 6sp
    OK, this is what you have to do:

    Behind the speaker in the LH (Driver's) footwell, is the compressor Lock Sensor.
    Remove hood release handle
    Remove left speaker kick panel / plastic cover
    Remove the speaker pod
    There is a plastic box on the inside lower wall of the body cavity, held on by 2(?) nuts on sheet metal. Nuts are outside, towards where your feet would be. Remove those
    Now you can reach down and fish the entire thing up and out of the hole.

    Great, so now you have this weird box with too many wires in your hand, what to do?

    You need to jumper 2 wires.
    The wires you need are these:
    pin #3 - Black/Red/Yellow
    pin #5 - Black/Gray (there are TWO of them that go to the same pin, use either one)

    Do NOT cut them out of the original circuit, but strip a bit of insulation off and jumper them together 3-5" before the connector (X77) to the box, tape up the splice & reinstall everything.

    Now you can use a new R134 Denso/whatever single wire compressor.
    Last edited by cartoonz; 10-29-2020 at 01:14 AM. Reason: color blind stupidity
    '91 Dinan 860 Stage III (new 6L engine)
    '91 Dinan 850 TT stage III (brand new engine) 21st Century Tech meets 18th Century Dinan...
    '91 850i 6sp (mint) (sold)
    '90 Dinan 750iL TT stage III (Guido - The Beast)
    '94 850 CSi The Detroit Auto Show car (restored to factory perfect) (sold)
    '96 850Ci, The George Carlin car
    ''73 3.0 csi, '08 535i, '03 X5 4.6is
    ...and a few other non BMW cars

  3. #3
    Join Date
    Oct 2016
    Location
    Shoreview MN
    Posts
    977
    My Cars
    Had a 1991 BMW 850

    Wiring

    I will post the wiring Diagram Tonight

    I did not do it as described above and my AC will only work on coolish days. I am going to go back in and look at this again.

    Thanks

  4. #4
    Join Date
    Dec 2014
    Location
    Los Angeles, California
    Posts
    144
    thank you so much!!!! Finally have cold AC blowing I want to cry I love you brother ��
    Last edited by shogun; 10-31-2020 at 09:35 AM.

  5. #5
    Join Date
    Jan 2005
    Location
    Japan
    Posts
    54,655
    My Cars
    11/88 E32 750iL+98 E36M3
    BMW TSB B64 11 92 (3569) E31 850, E32 750 AC compressor shut down

    Situation: AC compressor shuts down during heavy rain, or when driving thru deep standing water. The customer complaint is loss of cooling. The condition disappears when engine is stopped and restarted.

    Cause: The AC compressor clutch is disengaged by the slip monitoring function of the AC lock sensor control module. This module continiously monitors the engine speed and compares this to the AC compressor speed. The magnetic clutch of the compressor is automatically disengaged by the lock sensor module if the amount of slip exceeds 30%. The intent of this system is to prevent broken v-belt or reduced engine cooling if the AC compressor locks up. If the vehicle is driven in heavy rain or if standing water is spashed up into the engine compartment belt area, the v-belt and pulley may get wet enough to cause slippage in excess of 30%. The lock sensor control module perceives this as possible AC compressor lock up and opens the clutch circuit to prevent damage. The control module will remain in this state with the compressor clutch deactivated until the ignition is turned off and back on, clearing the condition.

    Note: in addition to slip monitoring, an engine coolant temperature check has been incorporated into the lock sensor module on E32 vehicles produced since 09/1989, and E31 vehicles since the start of production. If engine coolant temperature rises above 240 degrees F., the AC compressor clutch is pulsed off at regular intervals to reduce engine load. If the coolant temperature rises above 250 degrees F., the clutch is switched off completely. As of 09/1992 production the slip monitoring fuction of the AC lock sensor module will be dropped on both E31 and E32 models.

    Solution: If a customer complaint of AC cooling loss is received, the following items should be checked before proceeding with this repair:
    -AC compressor belt tension adjusted to specification
    -No oil leaks have contaminated the AC compressor belt, causing slip
    -AC system pressure is within specificaion, not overloading compressor and belt.

    If the above checks do not isolate the source of the slippage, proceed with the following repair. The remedy for this siwation varies with the model and production date of the vehicle. Refer to the appropriate ETM for diagrams showing connector, pin and control module locations.

    750iL vehicles from the start of production thru 08/1989
    Remove the lock sensor control module from the from the left hand side of the drivers footwell. The unit has 2 connctors, 4-pin and 5-pin and is located in the recesss of behind the kick panel.
    Unplug the connectors X77 and X80 from the lock sensor control module body.
    Remove pin 1 of connector X77 and pin 3 of connector X80 using a terminals removing tool.
    Cut off the terminals and connect the loose wires with an insulated crimp connector. Shrink tubing may also be necessary to prvide proper insulation.
    Tape or tie-wrap the loose wires with the other harness wires.
    Plug the connectors back into the control module, reinstall the control module and reinstall the kick panel trim.


    E32 750iL produced from 09/1989 thru 08/1991:
    Remove the lock sensor control module from the left hand side of the drivers footwell, the unit also has 2 connectors, 4-pin and 5-pin.
    Replace the lock sensor control module with p/n 61352233107 . This replacement module does not contain the slip monitoring function.
    Reconnect the electrical connectors and install control module and kick panel trim.

    E31 from start of production thru 08/1992:
    E32 750iL vehicles produced from 09/1991 thru 08/1992:

    Remove lock sensor control module from left side of driver's footwell. The unit has 1 connector with 10 pins and is loacted in the recess behind the kick panel.
    Replace the lock sensor control module with p/n 61358360039 , this replacement module does not contain the slip monitoring function.
    Reconnect and install....

    Parts information:
    lock sensor module 61358360039 10-pin type E31 from start thru 08/1992, E32 from 09/1991 thru 08/1992.
    lock sensor module 61352233107 , 9-pin type, E32 from 09/1989 thru 08/1991
    Shogun tricks and tips for the E32 series are HERE!

  6. #6
    Join Date
    Oct 2016
    Location
    Shoreview MN
    Posts
    977
    My Cars
    Had a 1991 BMW 850

    Diagram

    Wiring DiagramAC A26 Lock Sensor.jpg

  7. #7
    Join Date
    Jan 2005
    Location
    Japan
    Posts
    54,655
    My Cars
    11/88 E32 750iL+98 E36M3
    my collection of info for M70 lock sensor, lock sensor delete, started in 2010, also added above comments https://www.bimmerforums.com/forum/s...or-delete-info
    Shogun tricks and tips for the E32 series are HERE!

  8. #8
    Join Date
    Sep 2014
    Location
    Texas
    Posts
    219
    My Cars
    1975 Bmw 2002
    I was looking at the coloring for the wiring diagram and it says GR Means grey and GN stands for green. Are the wires going into pin 5 black green or black grey? I am going to do this soon I was just trying to confirm the right wires before I got everything apart.

  9. #9
    Join Date
    Feb 2010
    Location
    Hampshire UK
    Posts
    8,871
    My Cars
    99 840ci Sport Indv
    The full diagram is here - and there are a few different versions over the model years: https://www.meeknet.co.uk/e31/e31_91.pdf#page=311

    Wire colours are shown here: https://www.meeknet.co.uk/e31/e31_95.pdf#page=20
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


    My BMW Repair YouTube Channel
    My Current 840ci Sport Individual
    My Current 650ci Sport Individual
    My E31 Repair and Information Website
    My E38 Repair and Information Website
    My E63/E64 Repair and Information Website

    Chase - Heroes to a generation

  10. #10
    Join Date
    Sep 2014
    Location
    Texas
    Posts
    219
    My Cars
    1975 Bmw 2002
    Got my module out and the two wires at pin 5 are black and grey like the wiring diagram suggest. Pin 3 is black red and yellow. I think cartoonz made a small error. Just trying to be careful because I dont wanna splice wires incorrectly.

    I wanted to post a pic of the connector but I can’t figure out how at the moment.

  11. #11
    Join Date
    Feb 2010
    Location
    Hampshire UK
    Posts
    8,871
    My Cars
    99 840ci Sport Indv
    Probably no error - there were a few variants over the years!
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


    My BMW Repair YouTube Channel
    My Current 840ci Sport Individual
    My Current 650ci Sport Individual
    My E31 Repair and Information Website
    My E38 Repair and Information Website
    My E63/E64 Repair and Information Website

    Chase - Heroes to a generation

  12. #12
    Join Date
    Dec 2014
    Location
    Los Angeles, California
    Posts
    144
    Quote Originally Posted by Ericks2002 View Post
    Got my module out and the two wires at pin 5 are black and grey like the wiring diagram suggest. Pin 3 is black red and yellow. I think cartoonz made a small error. Just trying to be careful because I dont wanna splice wires incorrectly.

    I wanted to post a pic of the connector but I can’t figure out how at the moment.
    mine also didn’t match the diagrams if the wires are in the correct PIN numbers then it should be fine

  13. #13
    Join Date
    Sep 2008
    Location
    Santa Barbara
    Posts
    3,462
    My Cars
    91 Dinan860 & 91 850 6sp
    wire colors fixed... in my haste, I mis-labled the black/gray as black/green.
    Do it exactly as written (now) and it works perfectly.
    '91 Dinan 860 Stage III (new 6L engine)
    '91 Dinan 850 TT stage III (brand new engine) 21st Century Tech meets 18th Century Dinan...
    '91 850i 6sp (mint) (sold)
    '90 Dinan 750iL TT stage III (Guido - The Beast)
    '94 850 CSi The Detroit Auto Show car (restored to factory perfect) (sold)
    '96 850Ci, The George Carlin car
    ''73 3.0 csi, '08 535i, '03 X5 4.6is
    ...and a few other non BMW cars

  14. #14
    Join Date
    Sep 2014
    Location
    Texas
    Posts
    219
    My Cars
    1975 Bmw 2002
    Got the AC working today. Ice cold. Thanks for all the help.

  15. #15
    Join Date
    Sep 2011
    Location
    Madison, NC
    Posts
    159
    My Cars
    1991 BMW 850i
    Is this still required (AC lock sensor trick) for a 1991 BMW 850i? Are there any replacement compressors where this is NOT required?
    Thanks,
    Tom
    Last edited by Tomcat BMW; 06-25-2021 at 12:10 PM.

  16. #16
    Join Date
    Sep 2008
    Location
    Santa Barbara
    Posts
    3,462
    My Cars
    91 Dinan860 & 91 850 6sp
    Quote Originally Posted by Tomcat BMW View Post
    Is this still required (AC lock sensor trick) for a 1991 BMW 850i? Are there any replacement compressors where this is NOT required?
    Thanks,
    Tom
    The best replacement compressors are Denso - which do not have the 3 wires to the connector, and neither do most other replacement compressors.
    So yes, this is required if you go from 3 wire to single wire. Remember, the plug is the same, it just does not have the pulse generator in the compressor.
    '91 Dinan 860 Stage III (new 6L engine)
    '91 Dinan 850 TT stage III (brand new engine) 21st Century Tech meets 18th Century Dinan...
    '91 850i 6sp (mint) (sold)
    '90 Dinan 750iL TT stage III (Guido - The Beast)
    '94 850 CSi The Detroit Auto Show car (restored to factory perfect) (sold)
    '96 850Ci, The George Carlin car
    ''73 3.0 csi, '08 535i, '03 X5 4.6is
    ...and a few other non BMW cars

  17. #17
    Join Date
    Apr 2018
    Location
    Maputo, Mozambique
    Posts
    28
    My Cars
    E60 530D, 1600-2, E30
    Hi all,

    I have finally managed to fix my AC compreessor and refilled it. tested fine, no leaks and holding pressure. (all this was done with a direct power from the battery to the compressor feed wire).
    But no normal power at the compressor plug when the AC button is pressed on. So I believe either the sensor at the compressor or the Lock Control module are the culprit. I need to bypass wire 3 and 5 on the module as per Cartoonz instructions above.

    Question:
    Where is the A26 module located on a Right Hand Drive car?

    Behind the speaker in the LH (Driver's) footwell, is the compressor Lock Sensor.

    thank you

  18. #18
    Join Date
    Apr 2018
    Location
    Maputo, Mozambique
    Posts
    28
    My Cars
    E60 530D, 1600-2, E30
    Hi all.

    OK, found it, so it is located behind the left front speaker on the right hand car.
    But on my car, Pin 3 Black/red/Yellow is correct, but pin 5 is a blue wire. the Black/Grey (two wires) is on pin 1. Bridging both pin 3 and 5 or pin 3 with pin 1, still no power to the AC compressor.
    What to check next?
    Note that i am using the original Compressor with the 3 wires plug. direct 12v power on compressor and it works well.

    Please help.

    thank you

    pin #3 - Black/Red/Yellow
    pin #5 - Black/Gray (there are TWO of them that go to the same pin, use either one)

  19. #19
    Join Date
    Apr 2018
    Location
    Maputo, Mozambique
    Posts
    28
    My Cars
    E60 530D, 1600-2, E30
    HI,

    So I bridged pin 1 (Black/Grey (two wires) with pin 3 (Black/Red/yellow wire) and found that I had two misplaced relays on the fuse box, relay K19 and K33. swapped these around and the AC compressor works, great, but...

    the AC switches on as soon as I turn the air vent on, without depressing the AC button!! The AC button lights on but makes no difference, what am I missing?

    Any hints?, please...


  20. #20
    Join Date
    Jul 2020
    Location
    France
    Posts
    86
    My Cars
    850i
    For the 850i, the normal behaviour is:
    - the AC is on at start up for 15min (not always, depending on the externat temperature)
    - after those 15min, it will switch off if the button (and the light) is OFF

  21. #21
    Join Date
    Sep 2008
    Location
    Santa Barbara
    Posts
    3,462
    My Cars
    91 Dinan860 & 91 850 6sp
    Quote Originally Posted by Pulgalouka View Post
    Hi all.

    OK, found it, so it is located behind the left front speaker on the right hand car.
    But on my car, Pin 3 Black/red/Yellow is correct, but pin 5 is a blue wire. the Black/Grey (two wires) is on pin 1. Bridging both pin 3 and 5 or pin 3 with pin 1, still no power to the AC compressor.
    What to check next?
    Note that i am using the original Compressor with the 3 wires plug. direct 12v power on compressor and it works well.

    Please help.

    thank you

    pin #3 - Black/Red/Yellow
    pin #5 - Black/Gray (there are TWO of them that go to the same pin, use either one)
    You are misreading the pin placement on the plug... Blue wire is Pin #1
    Do NOT include that one!
    Jumper the black/red/yellow with the black/grey and that's it.

    As for your relay swapping... it sounds like whatever you plugged into K19 is either a "normally closed" (nc) relay or some other oddity.
    '91 Dinan 860 Stage III (new 6L engine)
    '91 Dinan 850 TT stage III (brand new engine) 21st Century Tech meets 18th Century Dinan...
    '91 850i 6sp (mint) (sold)
    '90 Dinan 750iL TT stage III (Guido - The Beast)
    '94 850 CSi The Detroit Auto Show car (restored to factory perfect) (sold)
    '96 850Ci, The George Carlin car
    ''73 3.0 csi, '08 535i, '03 X5 4.6is
    ...and a few other non BMW cars

  22. #22
    Join Date
    Apr 2018
    Location
    Maputo, Mozambique
    Posts
    28
    My Cars
    E60 530D, 1600-2, E30
    Quote Originally Posted by ben325 View Post
    For the 850i, the normal behaviour is:
    - the AC is on at start up for 15min (not always, depending on the externat temperature)
    - after those 15min, it will switch off if the button (and the light) is OFF
    Hi Ben325,
    I didnt know that, need to go read the manual again... either way, hope that this is the case and there is actually no issue. thank you

    - - - Updated - - -

    Hi CartoonNZ,

    thinking about it, you must be right... need to get some reading glasses.. the numbering letters are so small that I must have mistaken the one with the 5. What a relief...

    Regarding the relays, yes, when I did some work over the relay\fuse box a year or so, I must have mixed them up, go them right now.

    Hope this is actually normal, that the AC is on at start up for 15min and not a new problem I need to deal with. Will test it by running it longer this weekend.

    thank you very much to everyone

  23. #23
    Join Date
    Jul 2020
    Location
    France
    Posts
    86
    My Cars
    850i
    See the full description attached

  24. #24
    Join Date
    Apr 2018
    Location
    Maputo, Mozambique
    Posts
    28
    My Cars
    E60 530D, 1600-2, E30
    Nice info ben325, thank you.

    I did try it on Saturday, left it idling for about 20min but the AC compressor did not switch off, both the AC button and lights off. Didnt have more time as I had family matters to atted to, but since it works and all seems normal, I will leave it as is. I will consider it solved.

    New problem on sunday, the EML is not turning on for a few seconds like it should,,,, so new problem to deal with, I will check the cluster bulbs next weekend.

    thank you everyone

Similar Threads

  1. Replies: 13
    Last Post: 04-17-2021, 04:49 PM
  2. Operation of M70 lock sensor, lock sensor delete info
    By shogun in forum 1988 - 1994 (E32)
    Replies: 11
    Last Post: 11-15-2020, 07:44 PM
  3. HowTo-> A/C Check Lock Sensor, Break Device, IHKA Cycling between hot and cold
    By 85k100rt in forum E32 Common Problems and DIY Fixes
    Replies: 0
    Last Post: 06-24-2010, 03:18 PM
  4. Lock Sensor, Break Device, IHKA Cycling between hot and cold
    By 85k100rt in forum 1988 - 1996 (E34)
    Replies: 0
    Last Post: 06-24-2010, 01:52 PM
  5. E36 AC Pressure Sensor .. Where to buy CHEAP ?
    By ZONDERVANUS in forum 1991 - 1999 (E36)
    Replies: 0
    Last Post: 10-23-2007, 08:24 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •