GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 1999 🢒 Grand Prix 🢒 Body and Accessories 🢒 Seats 🢒 Heated Seats Circuit Description

Voltage from the DIC/HVAC fuse is fed through CKT 541 to the driver seat heated switch when the following conditions exist:

    • The ignition switch is in the RUN position.
    • The driver seat heater switch is in the LO position.

There are 3 sets of switch contacts in the driver seat heated switch:

    • The first set of switch contacts sends an ON signal to the driver seat heater control module through CKT 1462.
    • The second set of switch contacts sends a signal to the driver seat heater control module through CKT 1501 whether the switch is in the HI (no resistor) or LO (through resistor) position.
    • The third set of contacts determines if the HI or LO indicator is illuminated.

The following actions occur when the driver seat heater control module receives an ON signal from the driver seat heated switch:

  1. The driver seat heater control module closes the normally open set of relay contacts.
  2. The HSEAT/LUM fuse sends voltage along the following path:
    3. • Through CKT 2040
    • Through the relay contacts
    • Through CKT 950
    • Through the heated seat element in the driver seat back cushion cover
    • Through CKT 900
    • Through the heated seat element in the driver seat cushion cover
    • Through CKT 750 to G301
  3. Both of the heated seat elements heat the seat cushions.

The driver seat heater control module monitors the driver seat cushion cover temperature using the heated seat thermistor. The thermistor senses the current flow along the following path:

  1. Through CKT 952
  2. Through the heated seat thermistor
  3. Through CKT 750 to G301

The driver seat heater control module controls the relay output in order to maintain a set temperature. The module closes the relay until the set temperature is exceeded and turns off the relay until the seat cools.

The relay tries to maintain the following temperatures:

    • Approximately 37.5°C (98.5°F) for the LO position
    • Approximately 42.5°C (107.5°F) for the HIGH position

The system turns off when either of the following actions occurs:

    • The driver seat heated switch is set to the OFF position.
    • The ignition switch has been cycled OFF and then back to the RUN position.