I have a 98 S90 with about 140,000 miles on it. I've had it for about 3 years now and have had no problems until now.

About 3 months ago i notice that driving a lot in town my AC with blow ice cold for about 10-15min then will gradually start blowing warm air. When i turn the AC off for a few min it will again blow ice cold for 10-15 then gradually start blowing warm air. However most of the time when i drive on the interstate at around 65+mph it will blow cold for a lot longer and sometimes never start blowing warm air but as soon as i slow down to exit it starts to blow warm air. After researching possible diagnosis's i took one persons advice and drove it until the AC blew hot and pulled into a parking lot and popped the hood to see if the compressor was still running. Sure enough it wasn't.

My question: Is there a simple explenation to why my compressor would be shutting off while driving?

Other information: I have replaced the serpentine belt and the AC reciever/drier usually has condensation built up on the outside until compressor has shut off and it actually gets warm to the touch

 

My vote is the clutch needs to be reshimmed.

 

just had this problem on my moms S90.


it needed a new compressor and dryer. not sure if thats your case but thats what happened with us

 

USFBull56 - did you ever find out the issue? I have a similar problem. The A/C compressor and such were replaced less then 3 months ago, so I don't understand why the compressor would disengage.

 

Compressor will be shut down if there is not enough refrigerant pressure. What is your low-side pressure, and does it hold?

 

The pressure was on the high-side of the range, don't remember that actual number. I was not able to add more refrigerant due to the pressure. Would the pressure be high if the refrigerant was low? I have not noticed the issue in the last week as the temps are not reaching the upper 90s and 100s.

 

I doubt that's the case. When you shake the bottle refrigerant's pressure is a lot higher than the Low-side port. That's part of the reason why it is filled from the low-side port.


No.

 

You need to tell us the number -- psi at Low-Side port.

 

I'll see if I can find my prior post later, a lot of modern cars suffer from this problem with age and miles of A/C operation. The cause is wear on the faces of the magnetic clutch assembly (it cycles a LOT), which increases the air gap over time. When the compressor / clutch is colder the magnetic clutch is more effective an it will still pull into contact through the increased air gap. This problem occurred in spades on my wife's 1989 Ford Taurus with a poorly designed Nippon Denso supplied magnetic clutch, so I had to fix the Taurus about every 20k miles and I was well aware of the problem. I did this fix on our S90 at about 80k miles and it was still working fine at >130k miles when the head failed. Putting on a new compressor / magnetic clutch assembly also fixes the problem, but it is a LOT more expensive than the parts and more time consumming.

The fix is actually simple, Volvo sells a shim pack (maybe also the individual washers) for the S90 magnetic clutch assembly and you just need to select a shim that is a bit thinner than the one installed until you get to an air gap within spec (I go for the low end). Fortunately, the front plate is quick / easy to remove with a simple tools, which will let you get at the factory shim.