car?

hello, i have a ford focus 52 reg tdci and it is a damaged repairable. everything has been fixed and it runs well except for the fact that the heater only blows cold air and the temp gage obviously hardly moves up, apparently the hoses under the bonnet are hot, well so my friend tells me as he has had a look, but the heater still only blows cold air, and the car is freezing especially at night, is there a special valve or something that makes it get hot, if anybody can help i would be extremely grateful, thanks in anticipation, graham