triggering A/C compressor 1995 C280 W202 - PeachParts Mercedes-Benz Forum

TimFreeh · #1 05-08-2008, 08:46 PM

Quote:

Originally Posted by ke6dcj

My understanding is that the A/C compressor sends out a passive speed signal and it is upto the climate-control brain to compare the A/C compressor speed signal against RPM, and if the delta is too great the climate-control brain will disengage the clutch.

Which also means, if you don't have "brain" watching, the A/C compressor will just keep on pumping.

As long as your substitute for the "brain" continues to supply a +12 signal the compressor will stay engaged.

Quote:

Originally Posted by ke6dcj

BTW: if my understanding is correct, does this also mean that the pump when "on " is always 100% and doesn't use the speed-signal to vary pumping ?

Thanks,
:-) neil

The variable displacement A/C compressors that I've seen do not rely on electrical signals to modulate pump displacement. The compressors respond to pressure changes in the suction side of the system, low pressure (like 20-25 PSI) reduces displacement and higher pressures (like anything > 40 PSI) increases displacement. This is typically done via a swash plate with mechanical linkages.

No electrons required.

ke6dcj · #2 05-08-2008, 09:57 PM

Quote:

Originally Posted by TimFreeh

The variable displacement A/C compressors that I've seen do not rely on electrical signals to modulate pump displacement. The compressors respond to pressure changes in the suction side of the system, low pressure (like 20-25 PSI) reduces displacement and higher pressures (like anything > 40 PSI) increases displacement. This is typically done via a swash plate with mechanical linkages.

No electrons required.

Tim,
according to the linked article, starting in 2001 Denso started using "electrons" to change compressor displacement:

http://www.search-autoparts.com/searchautoparts/Teardown/ArticleStandard/Article/detail/156230

Since I'm looking at a 1995 compressor, the "old" mechanical method applies to me.

:-) neil