Subject: Seat Heating System Models: 924S/944/911/911 Turbo/921 ALL
Bulletin Number: 86 – 01
This Information describes the operation and function of the optional seat heating system.
Seat heating is activated by switching on the ignition and pressing the upper half of the heating switch (arrow is pointing to lower half).
Doing so heats the seat cushion surface and backrest in the area of the center section. Heating can be switched off by pressing in the lower half of the heating switch. As of March 25, 1986, an improved operating switch is used in production. The new switch features a rough surface for the “on” position. This aids the seat occupant in determining the position. Of the switch without having to look. In addition, the seat heating symbol is placed in the center of the switch lever. (Formerly at the “on” position).
New Switch Left PN 928.613.187.02
New Switch Right PN 928.613.188.02
Former version stocks will be depleted.
Switching on seat heating activates two (2) protective circuits.
- The seat heating/time relay, located under the seat near the motors, switches off seat heating after 15 minutes of continuous operation. Heating can be switched on again immediately afterwards.
- A (bimetal) temperature switch located near the heating element underneath the backrest, stops power flow though the heating elements when a temperature of 43 degrees C (100 degrees F) is exceeded. The heating elements will again receive power when the temperature switch is below 20 degrees C (68 degrees F).
These features ensure no damage from excessive heating.
Checking Heating Elements
The seal bottom and back elements are connected in a series circuit. If the power is interrupted in one of the two elements, neither will function. The heating elements can be checked separately via the pertinent plug connection at the heating elements.
Two methods can be applied:
- Checking with an ohm meter. Resistance approx. 1 ohm per element
- Connect a 6 volt power supply to the heating element and check for heating.
IMPORTANT: Never test with more than 6 volts, heating elements could burn through
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