The A/C on my brother's 190D will not turn on the compressor. When he bought it the mechanic said it would need a new relay. It has 360,000 miles on the odometer, would it be the relay or compressor? Last year, it would work every once in awhile. Is their a way to check if it is the relay? From other people's experiences, would it still have the charge of freon or do you think that it may have leaked out. Don't want to fix than find a leak somewhere.
Thanks
David

It could be either one. Mileage is no indicator.

I have an original relay but a newer compressor. The early compressors in 84 were quite problematic -- at one point it was the single biggest problem with a new 84 190D.

On the 84's make sure the front fan works (the compressor will seize if you run it in traffic without a working front fan).

You can make a slight press on the valves for the AC to see if there is any freon in the system.

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Jovan

'84 (11/83) 190D 2.2 5-Speed; Silver/Blue; Motor No. 00354, 402k mi (340+kmi mine)

'89 Porsche 911 Turbo Coupe; Black/Black; 53kmi
'05 BMW 530i 6-Speed; 302kmi
'19 Range Rover; 30kmi

Are the aux. fan and A/C compressor in any way connected. My aux fan died and my ac compressor won't turn on unles I bridge it manually.

Thanks

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1984 MB 300D Turbo Diesel W123 Sedan 132K
1987 MB 300D Turbo W124 Sedan 295K
1983 Porsche 944 104K
1989 Audi 80 Quattro 180K
2002 Audi A6 3.0 Quattro Avant 49K (Wife's car with warranty )

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Get your hands on a wiring diagram or better yet a shop manual that will describe how power gets to the compressor and what interrupts are in place to disable the compressor in the event of a system anomaly.

If the relay compares compressor rpm to engine rpm, diagnosis will require more than a simple electrical tester unless the problem is one of the simpler interrupts.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

Can anyone tell me where the relay is located?
Thanks
David

Howdy, I've never had to work on the A/C system, but I've got a '84 190D 2.2 and the MB CD-ROM for it. I'd certainly recommend buying the CD-ROM for a W201 as it has been very helpful in fixing things on my car so far.

The pressure switch itself is located on the receiver/drier It's a cylindrical barrel that is on a tee off the top.

The relay should be inside the pushbutton control unit (not such a good design idea). The output of this realy comes out of the control unit on a bl/gn wire to terminal 'O' on the fuse panel (engine bay) then goes out as a bl/ws wire on what looks like terminal 18. This goes over to the pressure switch at the receiver. The output of the pressure switch is a bl/gn wire that goes over to the compressor clutch.

You should really get the CD, it's good although some of the pics are fuzzy.

Anyway, there should be 12V on the pressure switch at the bl/ws wire if there is a call for cool. I'd disconnect it first and ohm out the pressure switch. Then I'd see if there actually is 12V at the switch. You could momentarily light up the compressor (AT YOUR OWN RISK!!!) using battery voltage. The brown wire coming out of the clutch is chassis ground: you could Ohm out that also: grounds have been known to go bad.

Sholin

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What else, '73 MB 280 SEL (Lt Blue)
Daily driver: '84 190D 2.2 5 spd.