2006 Ranger 3.0

I bought my ranger this year and since it was advertised as having A/C but in fact didn't, the dealership arranged to have it installed. It puts out cold air now which is good, but unfortunately it doesn't want to produce heat any more.

This has been troublesome since I can't use defrost in the morning, and of course the summer will end eventually.

Does anyone have any idea's as to why this would happen?

Thanks.

 

Could be many things (inoperable blend door is a common cause of this), but first I'd take it back to the dealer that installed the a/c.