hello:
my friend has a 2005 S80. I know its a turbo and he suspects it's a 2.5L.
He doesn't have heat. the individual temp selectors appear to be working because i can hear a change when you change the temp from cold to hot. but it only comes out mildly warm for a brief moment and then just goes mostly cool. the blower works fine. im pretty sure its the heater valve, but i cannot find it. can anyone describe it's location and send me a link to what it looks like? also, is it easy to replace or should i suggest he take it to the dealer? i have mediocre skills.

 

There is no heater valve that turns on and off the flow of (hot) water. (240's had one that sorta controlled flow, 740-940 had one that only mostly turned off in Max ac mode) Water flows all the time through the heater core. The air temp inside the car is controlled with blend doors - blending cold air from ac or outside with hot air from the heater core to get the temp you have called for.

 

Silly idea but.... these cars develop heater leaks inside the cabin, rather than fix it the plumbing may have been modified to eliminate the the leak Someplace to start anyway.