A/C compressor clutch makes noise

[htrdbmr]

Good to hear. My car also uses a Denso compressor, and a new or rebuilt clutch assembly is very expensive. The air gap is very important- should be as small as possible with the car at operating temperature. Also important is the head pressure, too high (over charged, dirty condenser, bad fan) will cause the clutch to slip. Slippage will ruin the unit in short order.

[shogun]

additional info on lock sensor, BMW TSB # 641192 http://www.bimmerforums.com/forum/sh...8360039-issure

[shogun]

...and in 2019 the compressor still works strong and without problems, complete success.

Additional info copied:

E31 850, E32 750 AC compressor shut down - TSB B64 11 92 (3569)

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 splashed 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 function 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 specification, 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 situation 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 connectors, 4-pin and 5-pin and is located in the recess 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 provide 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 foot well, 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 foot well. The unit has 1 connector with 10 pins and is located 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

Warranty status: parts and labor reimbursable. Defect code: 64 52 07 12 00

[shogun]

Did meanwhile a member with an 750 change the compressor from original M70 style with lock sensor to a non lock sensor version? If so, what did you do to eliminate the lock sensor? Which compressor did you use? On the E34 and E28 they use Sandem compressors and member demetk makes the brackets for the M30 engine
http://www.mye28.com/viewtopic.php?f...46318#p1046318
http://www.mye28.com/viewtopic.php?f...60555#p1260296

[shogun]

and another update, repaired compressor is still working perfect 9 years later

[shogun]

More details on lock sensor delete here https://www.bimmerforums.com/forum/s...or-delete-info

[shogun]

DIY: How to modify AC Lock Sensor for single wire compressors by cartoonz, posted in the E31 forum (for the M70)

Seems that all replacement R134 AC compressors these days seem to only have a single wire to the plug, rather than the 3 wires on the original. Plug is the same, but the compressor side just has the clutch activation wire.
So you bought a new AC compressor, charged up the system, and were mortified that the AC doesn't work anymore.
What to do?
Fear not, the fix is simple (but kind of a pain in the butt to get to).
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 -- and it will work just dandy
----------------------------------------

"What is this voodoo?", "Why does this work?", & "What did those wires do?" are common questions.

The original design used a Hall-IC to send out a square wave pulse that the "lock sensor" in question could monitor. The reason for this was to ensure that if the AC compressor was locked up and not moving with the clutch engaged, the lock-sensor would disengage the clutch to protect the drive belt from eating itself. The lock-sensor also monitors engine coolant temp and cuts the compressor off at some high limit temp as well. There is also an engine speed comparison circuit that checks that the engine is running over a few hundred RPM's before engagement. Pretty smart & slick design really, but not very useful when all the reasonably priced replacement compressors eliminate the Hall-IC circuit.

There is nothing reasonable we can do to "fool" the lock-sensor into thinking it actually sees a pulse, so no amount of trickery on the harness by the compressor will accomplish anything. We have to bypass the lock-sensor.

These wires are NOT either of the two now "extra" wires to the compressor from the car. The wires we are connecting together basically eliminate the relay in the sensor that control the compressor clutch protection scheme.

This will not negatively affect an actual 3 wire compressor either, but it will eliminate the lock-sensor all the same.

Now, since we have now bypassed that "safety circuit", we need to understand that if the compressor does freeze up, you could eat a belt. No way to avoid that anyway with a single wire compressor.
The compressor will also be oblivious to any engine overheating situation, although if you are really dependent on an AC compressor to tell you your engine is overheating, I'm not sure what to say.