Left heater control box. Losing heat in your passenger compartment? If your hoses and cables are all good then you will need this part. The later control box is commonly used, but this part is correct for earlier 911 and 912 models. For models starting in 1974 or later (911/912E/930) each box will need Heater Box Connecting Sleeve, part number 911.659.119.00, to make it work and fit.