03 Silverado with the manual slider controls for the driver and passenger sides. The passenger side is working fine, so i don't think anything is wrong with the heater core or a/c...but the driver side won't change from luke-warm. Just enough to make it hot if its over 65 and cold if its under 40, ug! Living in Colorado don't help with temp fluctuations, it's been about a week and definatly no bueno. So does anyone know what would cause this?

I was thinking it is probably the electronic controler behind the manual switch that is bad...should i just get behind the dash and have a look? or should i just take it in to the dealer?

any opinions?

 

anyone have any idea what may be causing this?