Hello,

My a/c compressor isn't engaging. I've jumpered the terminals at the Klima module and got the compressor to engage. I checked the continuity between the two spade terminals of the pressure switch near the drier and have found an open circuit through the switch. Is this normal or is this an indication of low refrigerant pressure?

Thanks

Jorg

Is It:
Low Refrigerant
or
Bad Switch
?

If you've NOT enough Refrigerant, even with a good Low Pressure Switch
You'll not get any Joy.
(And you don't wanna FORCE the compressor to run on LOW Freon,for very long)

'Got a set of gauges? (To check for Refrigerant)

If you jumper the wires that connect to the Low Pressure Switch on the R/D
Does the Compressor engage?

If you've got Freon and the Comp doesn't engage/BUT the comp engages
when you jumper the LPS wires ,It's the LPS that needs renewing.

The Open Circuit on the LPS is just telling you there's not enough pressure.
(Or you have pressure and the LPS has traveled South.)

Klima relay HAS been known to screw with more than one MB owner.

1. Check for proper freon level/pressure, correct as necessary.
2. Try "Jumpering" the LPS.
3. Then look askance @ the Klima.

__________________
'84 300SD sold
124.128

Thanks for the info.
Since I don't have access to guages at the moment I will jump the switch as a test.

Jorg

IS ,whether or not EVERYTHING else in the circuit/CCU system is working.

Still No resolution of:
1. Freon level
('Cause you're "Forcing" the System to engage the Compressor,by "Telling"
the System that the LPS is reporting Freon Level O.K.)
2. LPS function
(Same ,and you're "Cutting the LPS OUT of the Circuit")

'Favorite explanation from the Expert Arthur Dalton below

Attached Thumbnails

 

__________________
'84 300SD sold
124.128

Is there a way to test the Klima relay?

__________________
2009 Mercedes ML320 Bluetec

Thanks for that info.
I will check for 70-80psi with compressor off and proceed from there.

Jorg