Strange A/C behavior on 1999 S80

[avi8]

Hi there,

I've been having a very strange problem with the air-conditioning system on my 1999 S80. When I first got the car, I noticed that the A/C compressor would engage for a while, then disengage, then it would engage again, and then disengage, and so on. This is the intermittent pattern I've noticed with other S80s as well.

Lately however, the A/C compressor seems to just engage and keep remaining engaged. Further, when I have the temp knob at the coldest setting, it blows out super ice cold air, siginificantly colder than before. To get remotely warm air, I need to set it almost all the way to the hottest setting. Also, after I drive around for a while with the A/C on, and come to a stop, the A/C compressor seems to be making a "roaring" noise.

Another strange thing that seems to be happening is that, the fan could be set at a particular speed, but after driving around for a while with the A/C on, the flow of air emitted from the vents is "reduced". When I turn the fan all the way up to the max, it almost sounds like the flow of air is being "choked" or "muffled". This usually goes back to normal if I switch off the engine and restart the car.

Sometimes, if I drive on the highway for long-distance trips with the A/C on, there would be what seems like particles of "ice" coming from the vents.

To make things worse, after extended periods of A/C usage, it seems like a "burning" smell is coming from the vents.

So, in short, the symptoms are...
- Compressor keeps remaining engaged when A/C is switched on
- Air is super cold when at coldest setting
- No warm air until very end of temp scale
- Compressor makes roaring noises after a while
- Airflow changes from normal to "choked" after a while, ok after engine restart
- Burning smell from vents after a while, ok after engine restart
- Ice coming from vents after a while

I've taken the car to the local Volvo dealer as well as another mechanic, but everyone keeps telling me the A/C is working just fine.

Would you happen to have any ideas as to what could be causing this? I've been trying to troubleshoot the problem, but there seems to be so many components to the A/C system on this car. Any help would be much appreciated - Thanks!

[LaRy]

I have seen in the Swedish Volvo forum a lot of discussions about this problem. Finally, one Volvo technician informed that on the left side of the evaporator it is a sensor checking that it is not getting too cold ( = ice) in the evaporator. Then the ice is stopping the airflow. If you turn the AC off for a while, the ice is melting and the AC is working for an hour again. Solution, buy a new sensor and change it. It should not be any problem to change it, just replace it. Price in Sweden as sparepart, 25 USD. It is placed at the left side of the evaporator. Loosen the panel above the pedals. The sensor is found up to the right somewhere at the evaporator. It is fastened by a espanjolett locking function. The lengt is appr. 3 - 4 inches.
After this information it has been at least a dousin of greatful Volvo owners.
The same problem will eb found also at S60, S70, XC70 and S80

[codered741]

I am having the same problem as listed above, except with a '00 S80. I was wondering if you knew what that part was called, or even a part number would be nice. I found something called a thermostatic switch, but im not sure if that is it. Thanks for your help.

[LaRy]

A straight translation from Swedish would be "evaporator temperature sensor" placed in the CCM module.
The problem is that when this sensor is broken the regulator for the system gets wrong information. A broken sensor is normally givining false information that the temperature the fan house is 40 - 50 degrees + (Celcius), that is warm. Then the regulator is running the compressor at 100% capacity and the evaporator will freeze to ice. The air can not pass the ice, that's the reason why you don't get any air flow.
The Volvo workshop has the possibility to check this temperature sensor value by the diagnostic tool called VIDA.