Installing the PTC Cabin Heater

Steps for installation:

1. Remove the heater box
2. Remove the heater core
3. Construct a case for PCT heater to fit the heater core
4. Fasten the new PCT heater core to the heater box
5. Wire up the PCT heater

Modifying the Heater Controls

The heater should only run when the driver has set the heater to provide heat. Like most vehicles, the heater temperature control is variable and adjusts a flap which controls if air is routed through the heater core. If cabin heat is not required, the heater should be turned off. In order to do this, a small microswitch is placed on the heater control:

Here is show the dash controls; the underside (the protrusion marked A will be turned to position B to turn off the heat); and the installed microswitch in the "off" position.

Installing the PTC Heaters in the Heater Box

These are the two heaters, they have been expoxied together to form the approx same size as the stock heater core.

Once installed, the system is tested using 240VAC Mains power to the two heaters. With the fan on full a thermocouple measures the output temperature. The 3000W heaters put out 50^oC at the heater output.

Safety Systems

Electrical cabin heater elements, if not powered by fans could cause too much heat and melt the heater box. Several safety systems will be incorporated into the system:

• Thermal overload switch
• Heaters only on when power to the fan is on
• Heaters only on when fan is actually moving air

Cabin Heater Electrical Schematic

Relay control of the Cabin Heater

Each 1500W PTC cabin heater will be controlled by a single P&B 655-PRD-11DH0-12 relays. These relays are double pole relays rated at 250VDC at 20Amps. To get the required 312VDC rating, each pole of the relay will be wired in series with its' other pole.

Fuses for the Cabin Heater

Notes from Lee about some fuses:

For Bussman fuses; http://www.bussman.com, 314-394-2877.

Or for Littelfuse; http://littelfuse.com, 800-999-9445.

References