A/C clutch engages but not cold air - Mercedes-Benz Forum
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#1 (permalink) Old 01-20-2013, 03:41 PM
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Post A/C clutch engages but not cold air

99 C230 Kompressor. When I turn the a/c on, the compressor clutch will engage but only sometimes would blow cold air and the pressure on the low side will be in the normal range but will stop blowing cold air once I rev up the engine and the pressure will build up in the low pressure side and will stop blowing cold air but the compressor's clutch will be still engaged.
I can see the liquid moving through the glass window in the drier when the a/c blows cold but when the a/c stops blowing cold air the liquid will be stationary(would not move). I did unplug the a/c high and low switch in the drier and the clutch would stop; it would engage if i reconnect it again but the liquid through the glass would not move and the a/c wont blow cold air.
I replaced the condenser, drier, expansion valve, pag 46 oil in the compressor (4oz) after flushing the system and testing from leaks, vacuum the system and recharged it.
When the a/c blows cold air the low side pressure pipe on the compressor gets cold and the high pressure pipe gets hot but when it stops blowing cold air with the clutch engaged the low side pressure pipe on the compressor would get hot.
Any ideas?
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#2 (permalink) Old 01-20-2013, 10:23 PM
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The AC in my son's 2000 C230K cut out right after we bought it from a PP.

Also there seemed to be hot air coming thru the vents with nothing on.

The AC clutch engaged and the hi pressure line would get sweaty ice cold.

Shop determined that it was the duovalve and that this is common fault. In the engine bay, right hand side by the firewall.

Looks like the OEM one:

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I have read that they can be repaired but mine was replaced. You carefully take it apart and clean the gunk out that may be causing it to stick.

glenmore
1999, 2000 C280
2000 C230K
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#3 (permalink) Old 01-21-2013, 11:28 AM
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With the engine completely off, put your hand on the ac clutch and try to spin it. You should notice some resistance there, not a ton but some. If it freewheels easily, you may have a busted compressor. This may not be it, as your problem is intermittent, but its worth checking.
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#4 (permalink) Old 01-21-2013, 01:05 PM
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A/C not blowing cold

I cleaned the duovalve but the problems still persist. The clutch engages with the a/c on but no cooling and the glass window on the drier I can see the liquid. But there are times it blows cold air and I see the bubbles moving through the drier. Somehow it blow colds when it wants to and the low side pressure is within normal parameters but when it stops blowing cold air the low side pressure shuts up!
I can move the clutch with a tool at first but then I can move it easily by hand once I overcome the initial friction.
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#5 (permalink) Old 01-21-2013, 01:31 PM
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And the high side pressure is?
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#6 (permalink) Old 01-21-2013, 03:27 PM
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The high pressure side is high and the low side also high but whenever the a/c happens to blow cold air the low side pressure goes back to within normal ranges....but then after some mins it goes back to the same problem
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#7 (permalink) Old 01-22-2013, 05:04 PM
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And the pressures are?

Search the archives for reading AC system problems thru the controller.
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#8 (permalink) Old 01-22-2013, 05:45 PM
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low side pressure is over 100 and the high side is high; I can turn the clutch by hand.
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#9 (permalink) Old 01-22-2013, 06:28 PM
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Many C230's were not equipped with the digital climate control, so diagnosis is not possible through the console.

Since your drier has a sight glass, we know you have had some work done. I think that's normal on a 15 year old car. Do you have any records? When was the last service work done? What brand of compressor do you have?

You could have an overfilled/ underfilled system.

Or the cabin temperature sensor or the evaporator temperature sensor has gone bad. Without the digital system you can't possibly test to find out. An independent shop can read the codes, but that will cost money. Or you can buy the evaporator temp sensor yourself and install it, see if that fixes it.

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#10 (permalink) Old 01-23-2013, 06:50 AM
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What are pressures when system is stone cold and not turned on.

I assume you don't have a high pressure gauge?

As was said, your system may be overcharged.
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