Hello! i just picked up a 98 tahoe, the dash heater does is not providing heat, the rear heater works just fine. The pervious owner gave me some parts, a control unit on the dash and a bled door actuator, naturally I just slapped parts on, with no change. I put the actuator on the lower air box, the one above the transmission tunnel. Ive been reading here and this appears to be a common issue, where do start looking for the problem? I read there was another actuator on the top of the air box too.