I want AC but can't get the compressor to engage. Any thoughts AC is black magic to me. The test that my service CD told me to perform indicated that the kilma relay was bad. So since it is getting hot I spent $130 on that, needless to say it didn't do anything. So the car is a 1987 300SDL that was converted to R134 by a pretty good dealer in 1995. The kilma relay is new, but the compressor still will not engage. Any ideas?

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Low refrigerant. Have you put gauges on it to check the pressures?

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Rick Miley
2014 Tesla Model S
2018 Tesla Model 3
2017 Nissan LEAF
Former MB: 99 E300, 86 190E 2.3, 87 300E, 80 240D, 82 204D Euro
Chain Elongation References

You can also just short out the low pressure sensor on the receiver/dryer and see if the compressor kicks on. Doesn't tell you if its low on refrigerant or if the sensor is bad. But its easier than using gages unless you happen to already own them.

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'84 300CD Turbo 132k (Anthracite Grey) - WVO - My daily driver - Recently named coo-coo-coupe by my daughter.
'84 300D Turbo 240k (Anthracite Grey) - Garage Queen
'83 300D Turbo 220k (Orient Red) - WVO - Wifes daily driver

I'm not a certified mechanic, but I did stay at a HolidayInn Express last night.

From my learning lesson file - look at the inexespensive fixes first.
With engine running and A/C on pull the connector to the relay above thermo housing and see if your A/C comes on.

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BENZ THERE DONE THAThttp://www.peachparts.com/shopforum/...c/progress.gif
15 VW Passat TDI
00 E420
98 E300 DT
97 E420 Donor Car - NEED PARTS? PM ME!
97 S500
97 E300D
86 Holden Jackaroo Turbo D
86 300SDL
(o\|/o)

First let's determine whether you are getting power to the low pressure switch and compressor from the internal control unit--get a 12 volt test light and attach the alligator clip to a good ground. Then go to the low pressure switch on the drier pull off leads and test the wire end connections for power. If one lights up the test light, then you are getting power to the switch from the internal control unit. If not then your problem is electrical with the control unit or fuse. Then reattach the wires to the low pressure switch and do the same with the wires that go to the compressor. One should light up. If not, then you are probably low on freon or the pressure switch may be bad (less likely).

BTW, Autozone here will "lend" a set of gauges and a vacuum pump if you leave a deposit.

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1984 300SD 326,997 miles and counting . . . No wait, my odometer is still dead

For the record...
the pressure switch is the one to the side of the reciever/dryer... as compared to the temperature switch is above/on top and in line with the center of the R/D cylinder....

Ok I'll try some of those things you guys suggested. My dad and I will go threw it this weekend and see if we can't get it to work. Luckly my dad knows more about AC than me, I wouldn't hesitate to pull the head off or the tranny, but AC/electrical work are off limits. We got the compressor to engage by jumping two terminals that the kilma is plugged into. Maybe I should rent those guages from Autozone and see if I have anything in their.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Pay close attention and learn the a/c work. You will be surprised how easy it is - the freon/pressure side anyway (in my opinion). A good resource is www.ackits.com.

good luck

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Jim