HI . Can anyone help me identify this problem. MY HEater only works I.e blows hot air when im putting my foot down. When Im driving slow it only blows cold air and the car over heats. ANY IDEAS???????????????????????????????????

 

Hi Ya

Exactly the same as i had a couple of days ago.
Cold air out of fan,temp gauge right up,and hot air when foot down.

I checked my header tank and to my suprise it was empty,i filled up and all is working as it should now.
I was very concerned why and where the water had gone,On inspection i have found bottom of rad weeping.
I think that when the coolent is very low,you dont get any water through the heater matrix until you put foot down.
i hope this helps.