I bought my s40 used, and I think it's been an ongoing problem (3months) where the ac will (sometimes) kick on, and then randomly kick off . There's no real pattern that it follows. When it kicks on, the cold is ice cold, but when it shuts off, I always smell this stale air, sort of like slightly damp sand, then it will just blow hot air. Sometimes the ac will kick back on, but usually not. I have noticed though, that the fan in the front of the car does not always kick on high speed when I turn the cold on. When it does, I can feel the car shudder. I do hear the compressor sort of whine each time, though that may be the vent doors opening, I am not sure.

Also, not sure if it contributes, but my heater core leaks. I need to replace it too, but so far I have no idea where to buy them, other than just taking it to a volvo dealership or another mechanic.

 

The A/C is a known issue and a very easy and cheap fix. It is known as "reshimming" the compressor. It is in reality "deshimming" as 1 of 3 shims are removed from the A/C compressor clutch to move the clutch faces closer together. It might take an hour or two going VERY slow to fix it yourself with basic tools. You do not have to remove the compressor on the 2005 either. Look at this thread for more information.

https://volvoforums.com/forum/volvo-...shimming-6665/

No help with the heater core leak.

Here is the wheel well on the 2005 with the plastic liner removed:

 

After working on it today with my dad, we could not get the clutch face off. However it was determined the clutch was engaging properly, but the ac itself was not cycling ( turning the clutch off and on periodically to defrost ). We swapped some fuses and let it run, but it would still not cycle the clutch. I am not sure what the next step would be.

 

Help me understand a bit better. You turned on the A/C and the compressor clutch engaged but it did not cycle on/off, it just stayed on all the time? Or it would not engage at all?

A low charge of R134a would cause the compressor to run all the time. With the compressor clutch engaged did you check the sight glass on the receiver/dryer for bubbles? Many small bubbles indicate a very low R134a refrigerant charge. As more refrigerant is added the bubbles get larger and larger until they disappear. The moment they disappear is the moment you stop filling.

You must realize that idling a few minutes in the driveway in not the same thing as you described in your first post. You described ice cold A/C that would randomly kick off upon which the air would grow warm and stale. This is a perfect description of a compressor in need of deshimming. You could still have a low refrigerant charge as the two issues are not related.

For your heater core leak. Are you sure it's coolant leaking? You get that sickly sweet smell of coolant inside the car? Your carpets are stained? I ask because the S40 is famous for the sunroof drains leaking inside the car. But that's just rainwater, not coolant. There is also a known issue of the evap drain leaking under the carpet. Again, just water, not coolant.

 

Yes, we took the wheel off and watched the AC as it would engage and stay engaged. We also turned the AC on and off, and it would disengage and re-engage as it should. However, even though at idle, it did not ever disengage by itself. Even if we turned the temperature dial to hot, the clutch was still active and my dad said that it should turn off, and obviously it's something else that's wrong.

I was unaware to look at the receiver/dryer, and frankly have no idea what that is or where it is.

As for the heater core, yes, it does leak coolant, and I have to refill the reservoir every so often.

 

Well I guess I'm done then. Maybe time for professional help.