how do you make the air compressor runl onger and turn off for shorter periods of time? is it situated on the expansion valve?

no ideas?

I suspect you could undercharge the system with refrigerant to accomplish this but for the life of me I can't understand why?

I've never seen an adjustable expansion valve.

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Sam

84 300SD 350K+ miles ( Blue Belle )

If the compressor is disengaging when it shouldn't, the evaporator low temp cut out switch might be the problem. It is intended to prevent the evaporator from freezing, but they sometimes malfunction and actuate at a much-to-high temperature.

Any idea what model car you are dealing with?

Cervan,
What year and model. There can be different ways/ different models.

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

well my father insists that there is an ajustment that will tell the compressor when and how long to run is this all done automatically? sorry my car is a 1981 240d

Is there a particular problem that you are trying to solve?

the compressor is turning off abit too early i want the compressor to run longer when it is running and the wait time between runs to be shorter ( i live in california very hot out here doubt i can ice the evaporator over)

This could be your problem:
http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1YC1BU6YY21D1D7CJ3&year=1981&make=MB&model=240-D-002&category=R&part=A%2FC+Evap+Temp+Sensor

You might try pulling the sensor (wire) out of the evaporator and see if anything changes.

Is the A/C blowing cold when the compressor is engaged?

yes but my only problem is that i want it to run longer is this all computer controlled? so does that mean its computer controled for optimum coldness?

When the compressor disengages, how long does it take before it comes back on?

long enough for the air coming out of the vent to be 10degrees less than room temp.

Sounds like the evaporator temp sensor.

This is the sensor that tells the compressor to kick off to keep the evaporator from freezing over. Its located beneath the passenger side kick panel under some insulation. I think from what I've gathered in my readings that it is set a little conservatively, like around 38*F to make sure the evap doesn't freeze. It does have an adjustment screw so, as long as the rest of your system is up to snuff, you can adjust the sensor to kick off at a lower temp, causing the compressor to run for longer periods of time and making the air colder.

I haven't done this myself yet, as I spent last season just getting my system in working order but since its now starting to get into the 70s and 80s, I'm going to be doing this adjustment myself soon.

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Seth

1984 300D 225K
1985 300D Donor body
1985 300D Turbo 165K. Totaled. Donor Engine. It runs!!!
1980 300SD 311K My New Baby.
1979 BMW 633csi 62K+++? Dead odo

You have a 240D. Not only does it not have a computer, but I don't think you can even drive with a laptop in the back seat......
On a more serious note, what they said above. Your dial is set to max cold, right?

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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John