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95 960 Clutch Repeatedly Engages/Disengages 900

posted by someone claiming to be 960 Brickster on Wed Nov 12 00:20 CST 2008 [RELATED]

I am trying to troubleshoot the AC in my 95 960 sedan. The system was rebuilt in 2006, with new/used condenser and receiver dryer. At this time I replaced all O rings with new, and the orifice valve with a variable one. The system was evacuated, oiled, and recharged.

Mid summer 2008 I had to replace the interior light fixture, which included the temperature sensor. Some believe that this sensor is the cause, and this seems to be about the same time it stopped cooling. However,last weekend I put a new sensor in, and the AC still blows cool/warm.

Yet today the air is cool, but not cold. The AC clutch sounds like it is engaging and disengaging over and over. I had the system pressure tested and it is fine.

Not sure what the cause is. I would like to get a handle on the cause now, as there are many parts on sale due to the season. Ideas appreciated because my wife will not complain about AC not working until May 2009.

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95 960 Clutch Repeatedly Engages/Disengages 900

posted by dewfpo on Thu Nov 13 05:15 CST 2008
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last visit: Thu Oct 23 18:34 CST 2014

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You can get a cheap gauge at Wal-mart. You should check the pressures with the compressor cycling. It should be running between 25-42 psi or thereabouts. If it is and it is just cycling quickly, a top-off is typically the cure. If the pressures aren't right; and it's not overfilled, it could be a bad pressostat. Cheap and easy to replace. Let us know what pressures you are experiencing.

DEWFPO
--
1998 S90 077,400 and 1995 964 154,100

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95 960 Clutch Repeatedly Engages/Disengages 900

posted by howdy_doody on Mon Nov 17 11:22 CST 2008
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last visit: Sat Feb 27 14:47 CST 2010

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I agree, if it's like my Volvo, you can only check the low side, which won't tell you if you have a low charge (which I suspect is the problem).

The safe way is to evacuate and recharge with the correct amount. Use some dye so you can find the (obvious) leak. Or have it professionally leak tested.

The unsafe way is to add R134 untill the lines at the accumulator are cold. The problem is you may add too much, which will also result in a poor running system.

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Pressostats 900

posted by someone claiming to be 960 Brickster on Sun Nov 16 17:13 CST 2008 [RELATED]

I had the system pressure tested and it is reported to be fine. Haven't tested it myself. The pressostats are rust free, as I spray them with grease before winter.

However, in the summer I remember unclipping one of the pressotats when working in the area. Reclipped it on. Could this be the cause? Not sure if unclipping a pressostat causes a problem. How expensive are these, and how difficult to install?

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Pressostats 900

posted by dewfpo on Mon Nov 17 04:03 CST 2008
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last visit: Thu Oct 23 18:34 CST 2014

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Hi,

There's one pressostat. It's on the top side of the receiver/dryer. It is pointed towards the driver. I'm confused by what you mean when you say they are rust free and you spray them with grease before the winter. There are pressure sensors (1-3 depending on the year) on the front passenger's side of the condenser. Those control the engine fan speed and hi pressure cut-out. The last time I purchased one it was about $45 (Volvo OE). It takes all of about 2-3 minutes to put in.

DEWFPO
--
1998 S90 077,400 and 1995 964 154,100

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Pressostats 900

posted by someone claiming to be 960 Brickster on Mon Nov 17 09:41 CST 2008 [RELATED]

Hi, thanks for the clarification. Yes, I meant the 3 pressure switches on the bottom passenger side of the condensor. In the snow belt where I live, these frequently rust and rot a hole in the condencer.

If I am looking at the receiver dryer pressostat sensor,what can I check visually or test to eliminate as the cause? I put in a new receiver dryer in 2006.

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Pressostats 900

posted by dewfpo on Mon Nov 17 11:27 CST 2008
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last visit: Thu Oct 23 18:34 CST 2014

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The simplest way to check for the correct operation of the pressostat is to put a gauge on the low side and run the AC. The pressostat should energize the compressor clutch at ~42 psi and de-energize it at ~25 psi.

DEWFPO
--
1998 S90 077,400 and 1995 964 154,100

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95 960 Clutch Repeatedly Engages/Disengages 900

posted by Chris Mullet on Wed Nov 12 00:44 CST 2008
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last visit: Fri Oct 24 09:08 CST 2014

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If the system is producing the correct pressures yet it still clicks on and off, then possibly the pressostadt sensor is out of whack. Someone on this BB once said there is an adjustment screw on the bottom of them but I can't verify that.

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