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Old 05-15-2001, 11:21 PM
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On my 89 260 E 124 the ac clutch does not kick in,,,,any ideas on what to check , what is most likely to have gone on strike?

Thanks A bunch
Sweating in California.
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Old 05-16-2001, 01:19 AM
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Join Date: Mar 2000
Posts: 517
Several faults could result in an inoperative compressor clutch. Assuming intact wiring and fuses, the mostly likely cause is an inadequate refrigerant charge: the clutch (and thus compressor) is rendered inoperative if system refrigerant pressure falls below a set level. The Nippondenso compressor used with this vehicle has no oil sump and depends on the refrigerant to carry its oil.

If gauges are unavailable, a quick check for adequate freon charge can be accomplished by momentarily depressing the Schrader valve located on the return (low pressure) line. If minimal or no pressure is present, then the system likely has an inadequate freon charge (as well as a leak) and is thus inactivated by the freon pressure switch.

If the system is charged, locate the freon pressure switch (two pronged switch adjacent to the inflow side of the receiver/drier), disconnect and jump the two leads; turn the ignition on and activate the A/C (no need to start the engine). If the compressor clutch is heard or seen to engage, then the freon pressure switch is likely defective.

BTW, has the evaporator ever been replaced?
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Old 05-16-2001, 09:37 AM
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Join Date: Jun 2000
Location: Plano, TX
Posts: 2,476
Good post from jgll. I'll add one thing.

I'm not certain the a/c compressor clutch will engage
without the engine running. It likely depends on the
particular model/year of the car.

My 1987 124 uses the dreaded Klima relay to control
compressor clutch engagement. One of the functions of the
Klima relay - at least on diesel models like my car - is
to deactivate the compressor when engine RPM falls below
a certain level. In my car, the compressor won't engage
unless the engine is running at 600RPM.

Early Klima relays waited for 10 seconds after the engine
reached 600RPM to engage the compressor. This was really
annoying down here in Texas. The newer Klima relay I now
have installed seems more aggressive in engaging the
compressor, but I'm still certain it waits until the
engine is running.

As they say, YMMV.

- Jim
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Old 05-16-2001, 10:40 AM
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Join Date: Mar 2000
Posts: 517
Jcyuhn is correct; on vehicles equipped with a single poly-V-belt, the engine will need to be running when attempting to check clutch function by means of a jumpered low pressure protection circuit. Earlier vehicles with a dedicated A/C compressor belt can be checked in an ignition on/engine off position.
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