foggy windshield in rain - not an AC problem

[Retired MVS Contributor]

It does make sense to run the air conditioner in cold weather, in fact automatic climate control systems are designed to do just that...The AC evaporator condenses the moisture out of the air keeping it from fogging the windows...The condensed moisture is drained to the outside...The heater core, which will be warm, keeps the condenser from icing...As recommended by the manufacturer, running the AC year 'round keeps the AC compressor seals, o-rings, etc from drying out, hardening, and leaking...It does not run constantly and the amount of gas used is negligible...

jerrymcc,
I think you mean, to keep the evaporator from icing. The condenser is always hot when the compressor is running. You are definitely right about it being wise to run the AC in winter, if you don't you can get a leak. Three of my four Volvos have the manual climate control and I very seldom need to turn on the AC. If petrhick always has to run AC to defrost then something is wrong unless he lives in an extremely humid climate.

petrhick,

You are right, I had a senior moment and I know better...
You need to check for plugged drains. Besides the 2 big drains you see at the firewall, you will see 2 more when you lift the big cover to get to the cabin air filter.

[Retired MVS Contributor]

Check that rear vent under the floor at the left quarter panel...If the fan-forced air has nowhere to escape, pressure will build up in the cabin and the fan will run faster and roar since it cannot effectively move air anymore...That vent might be blocked by a rag, tool bag, etc...When the fan is running and making that roar, open a window and see if it changes pitch...