Heater Control Boxes & Ductwork

 

The Heater Control Boxes (993.572.786.00) hang below the engine and are held in place by its inlet and outlet red neoprene hose ducts. I know this from personal experience that if one of the ducts slips off a box, the box can hang down, drag on the ground, and get ripped off or damaged.  A damaged or missing box may allow exhaust fumes to enter the cabin, and so it should be addressed as a safety issue.

For these reasons, the Heater Control Box ducts should be inspected at each oil change for rips or misalignment. If they seem to be hanging low, it indicates a problem.
Getting to the boxes is easily done by putting the rear of the car on jack stands, removing the rear tires, and reaching under the car through the wheel wells, one of the easier DIY projects.

A new Heater Control Box costs $1,000 from Porsche distribution,

or between $250 and $500 on eBay. The 72mm inner diameter (ID) duct material (000.043.205.04) is only sold by Porsche Distribution in bulk lengths at several hundred dollars each, and then one cuts a section to the required working length. It can also be purchased in precut lengths on eBay for $25 to $30.

Although the cut lengths are 45mm or 80mm, depending on location, one can consider adding 5 to 10 millimeters to the specified cut length to ensure a tight fit and keep the boxes in position.

The original hoses installed during car assembly appear to have thicker walls reinforced with cloth plies, whereas the Porsche Distribution replacement hose has a thinner wall without reinforcement and may not be as durable.
Amazon offers a 70mm ID silicone duct in black that appears to have the

cloth ply reinforcement, and being just 2mm smaller than the 72mm ID specified in the Porsche parts catalog, may be a durable alternative.
Also, the original duct clamps may be misshapen and fail to adjust, so it may be advisable to replace both clamps per hose. They are inexpensive “European Style” hose clamps on eBay or Amazon. The hose clamps sold at a hardware store have wider bands and may not work as a direct replacement for the duct clamps.

 

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