GM Service Manual Online
For 1990-2009 cars only

Fuel Operated Heater (FOH) Van Models Only


Object Number: 1761443  Size: B4

If the vehicle includes an FOH, it will enhance heater performance and will reduce the amount of time it takes to warm the inside of the vehicle in cold conditions below or equal to 39°F (4°C). The FOH is installed on the frame rail on the driver side of the vehicle and uses diesel fuel to heat the engine coolant, which warms up the passenger cabin air.

The FOH will turn on if all of the following conditions exist:

    • Outside air temperature is below or equal to 39° F (4°C).
    • Fuel level is greater or equal to 12.5 percent of the total fuel tank volume.
    • The engine is running.
    • Coolant temperature is less than 167° F (75°C).