Not 100% sure but a couple of simple things to try...make sure the airmix lever is all the way up so that could outside air isn't mixing with the heat. Try using the a/c in manual mode and see if you can get heat. If none of that works I would think it's most likely that you air damper isn't working any more and allowing outside air in. Do you hear anything when you press the recirc button? If it's working you can hear the actuator opening and closing the recirc damper.

 

Actually, be sure that the air mix wheel is rolled all the way down.

 

That's what it was. I couldn't see the switch last night since it was dark but I turned it down today and sure enough that's what did it. Thanks!

 

^that is in confilct with the information on p. 35 of the owners manual.

 

And that page is in conflict with the air mix valve.
The OMs for 98 & 99 are incorrect. It took a few years,
but Volvo finally corrected it on page 37 in the 2000 OM.
No biggie - Misprints happen. Even to Volvo.

 

You're right. Volvo's crack manual writing team strikes again!

Just to be sure, any chance there was a design change on the HVAC system in 2000 that may have neccisitated that edit in the manual?

It actually makes more sense to work the way it says in the 2000 manual.

 

Nah... Changes cost money! Even Volvo knows that.
And if the book IS right, my dashboard is backwards.