Porsche 356C Heater Parts Diagram: A Complete Guide to Understanding Your Heater System

Understanding the heater system in your Porsche 356C is essential for maintaining cabin comfort and preserving the car's originality. Even if you're not planning a full restoration, knowing how the heater works and being able to identify its parts helps with troubleshooting, maintenance, and sourcing replacements. This guide provides a detailed look at the heater parts diagram for the Porsche 356C, covering each component and its function.

Heater System Overview

The Porsche 356C uses a fresh-air heating system that draws heat from the engine's exhaust. Hot air is routed through a heat exchanger and then into the cabin via a series of ducts, hoses, and a heater box. The system is controlled by cables and levers inside the car. The diagram below (described textually) shows the main components and their connections.

Heater Box Components

The heater box is the central unit, typically located under the dashboard or in the front trunk area (depending on year and market). Key parts include:

Heater Core

• Description: A small radiator-like unit that transfers heat from engine coolant to the air passing through it. The 356C heater core is compact and mounted inside the heater box.
• Identification: Look for a rectangular metal unit with inlet and outlet tubes. It may have foam seals to prevent air leaks.
• Common Issue: Leaks and corrosion over time. If coolant appears inside the car or the heater smells sweet, the core may be failing.

Heater Control Valve

• Description: This valve controls coolant flow to the heater core. It is typically operated by a cable from the dashboard lever.
• Types: Early cars used a simple on/off pull valve; later cars had a proportional valve for variable heat.
• Location: Usually mounted on the engine side of the firewall or near the heater core.

Heater Fan (Blower Motor)

• Description: An electric fan that draws outside air through the heater core when the fan switch is turned on. Not all 356C cars had factory blower motors; many relied on ram air from forward motion.
• Location: Attached to the heater box assembly.
• Troubleshooting: If the fan doesn't work, check connections, ground, and the fan switch.

Defroster and Floor Vents

• Description: The heater box directs air to either the windshield (defroster) or footwells via flaps. These flaps are controlled by cables.
• Parts: Flap doors, pivot arms, springs, and gaskets. Worn gaskets cause air leaks and reduced defroster performance.

Heater Hoses and Ducts

The system uses a network of hoses and metal ducts to move air and coolant.

Heater Hoses (Coolant)

• Description: Two hoses connect the engine's water jacket to the heater core. One supplies hot coolant, the other returns it.
• Sizing: Typically 5/8-inch or 3/4-inch inner diameter. Use silicone or reinforced rubber hoses rated for coolant.
• Routing: From the engine through the firewall to the heater core. Check for kinks or collapsed hoses.

Air Ducts

• Description: Flexible or rigid ducts carry air from the front grille (or cowl intake) to the heater box, and then from the box to the vents.
• Common Materials: Original cars used cardboard or fiberboard ducts wrapped in cloth; replacement options include plastic or modern reproduction parts.
• Sealing: Use foam tape or duct sealant to prevent leaks.

Control Cables and Levers

The heater controls in a 356C consist of one or two levers on the dash (or under dash) that operate cables going to the heater valve and flaps.

Cable Types

• Pull Cables: Used for on/off coolant valve. A simple Bowden cable with a knob.
• Push-Pull Cables: Used for flap doors. They can be either push-to-close or pull-to-open, depending on application.
• Routing: Cables run from the cabin through the firewall to the engine bay. Ensure proper lubrication and no sharp bends.

Lever Mechanism

• Dashboard Lever: Mounted on a bracket with a spring to return to closed position. Over time, the lever or bracket may break.
• Repair: Replacement levers are available from parts suppliers. Check the cable end connections for wear.

Electrical Components (If Equipped)

If your 356C has an electric blower motor, there are additional electrical parts:

• Blower Motor: 6-volt (or 12-volt if converted). The motor may have a resistor for speed control.
• Switch: A two-position toggle or rotary switch on the dashboard.
• Wiring: The circuit is simple: power from the fuse box, through the switch, to the motor, and ground. Check for corroded connections.

Heater System Operation

Here's how the system works step by step:

1. Engine coolant heats up, flowing through the engine water jacket.
2. When you pull the heater control lever, the cable opens the heater control valve, allowing hot coolant to flow into the heater core.
3. Air enters through the front cowl or grille (often via a scoop) and passes over the heater core. If your car has a blower, the fan forces air through.
4. Hot air then goes to the flap doors, which direct it to either the defroster vents or footwell vents.
5. When the lever is pushed in, the valve closes, stopping coolant flow and the heater core cools down.

Common Issues and Troubleshooting

No Heat

• Probable Cause: Coolant valve not opening (check cable adjustment). Low coolant level. Air lock in coolant system. Heater core clogged.
• Fix: Verify cable movement at the valve. Bleed cooling system. Flush heater core if necessary.

Weak Heat

• Probable Cause: Partially closed valve. Air duct leaks. Heater core fins clogged with debris.
• Fix: Inspect ducts for holes or disconnections. Clean heater core fins with compressed air.

Heater Fan Not Working

• Probable Cause: Blown fuse, bad switch, motor seized, or wiring fault.
• Fix: Check fuse; inspect switch continuity; test motor by applying power directly.

Coolant Leak Inside Car

• Probable Cause: Heater core leaking. Check for wet carpet or coolant smell.
• Fix: Replace heater core, inspect hoses and fittings.

Replacement Parts and Sourcing

While we do not recommend specific marketplaces, quality replacement parts for the 356C heater system are available from several sources:

• Original Equipment (NLA): Many original parts are no longer available, but good used parts can be found through club classifieds and swap meets.
• Reproduction Parts: High-quality reproduction heater cores, hoses, cables, and gaskets are produced by specialists in vintage Porsche parts.
• DIY Repairs: Some parts, like cables and gaskets, can be fabricated or adapted from universal components.
• Porsche 356 Clubs and Forums: These communities are invaluable for finding rare parts and getting advice. Members often have diagrams and manuals.

Final Recommendation

To successfully work on your Porsche 356C's heater, start by obtaining the factory workshop manual and a good set of parts diagrams. These show exact routing and part numbers. Use the diagram in this article as a general guide, but verify details for your specific model year and chassis number. When repairing, replace all hoses and gaskets at once to prevent future leaks. Test the system before reassembling the interior. If you are a novice, consider joining a local 356 club or hiring a specialist who knows these cars thoroughly. A properly functioning heater not only adds comfort but also increases the value of your vehicle.