Motorraum: Klimakompressor Lock-Sensor

[Erich]

weitere Ergaenzung zum Thema, diverse Teilnummern Infos:

Group 64 Heating and Air Conditioning B 64 11 92 (3569)
Woodcliff Lake, NJ Product Engineering June 1992

SUBJECT: Air Conditioning Compressor Shutdown
MODEL E31, E32 75OiL

Situation:
Air conditioning shuts down during heavy rain, or when driving through deep standing water. The customer complaint is loss of cooling. The condition disappears if the vehicle is stopped and restarted.

Cause:
The air conditioning compressor clutch is disengaged by the slip monitoring function of the Air Conditioning Lock Sensor Control Module. This module continuously monitors engine speed and compares this to the air conditioning 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 air conditioning 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 pulleys may get wet enough to cause slippage in excess of 30%. The lock sensor control module perceives this as possible air conditioning compressor lockup, 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 control module on E32 vehicles produced since 9/89, and E31 vehicles since the start of production. If engine coolant temperature rises above 240 degrees F, the air conditioning 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 9/92 production, the slip monitoring function of the Air Conditioning Lock Sensor Control Module will be dropped on both E31 and E32 models.

Solution:
If a customer complaint of A/C cooling loss is received, the following items should be checked before proceeding with this repair:

A/C compressor belt tension adjusted to specifications

No oil leaks have contaminated the A/C compressor belt, causing slip

A/C 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.

#1 E32 75OiL vehicles from start of production through 8/89:

Remove the Lock Sensor Control Module from the left hand side of the driver's footwell. The unit has two 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 terminal removal 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 to the other harness wires.

Plug the connectors back into the control module, reinstall the control module, and reinstall the kick panel trim.

#2 E32 75OiL vehicles produced from 9/89 through 8/91:

Remove the Lock Sensor Control Module from the left hand side of the driver's footwell. The unit has two connectors (4 pin and 5 pin) and is located in the recess behind the kick panel.

Replace the Lock Sensor Control Module with P/N 61 35 2 233 107. This replacement module does not contain the slip monitoring function.

Reconnect the electrical connectors and install the control module. Reinstall the kick panel trim.

#3 E31 vehicles from start of production through 8/92:
E32 75OiL vehicles produced from 9/91 through 8/92:

Remove the Lock Sensor Control Module from the left hand side of the driver's footwell. The unit has one connector (10 pin) and is located in the recess behind the kick panel.

Replace the Lock Sensor Control Module with P/N 61 35 8 360 039. This replacement module does not contain the slip monitoring function.

Reconnect the electrical connector and install the control module. Reinstall the kick panel trim.

Parts Information :
Lock Sensor Module 61 35 8 360 039

(10 Pin type: E31 from start through 8/92,
E32 from 9/91 through 8/92)
Lock Sensor Module 61 35 2 233 107

(9 Pin type: E32 from 9/89 through 8/91)

[Erich]

und noch eine Ergaenzung aus dem E31 Forum BF von cartoonz

DIY: How to modify AC Lock Sensor for single wire compressors


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.