How do you use the built in compressor on a 1998 Pontiac Transport Montana?

The 1998 Pontiac Transport (which is essentially a rebadged Chevrolet Venture/Oldsmobile Silhouette) doesn't have a built-in air compressor in the sense of a portable air compressor you might use for tires. It has an air conditioning compressor, which is part of the vehicle's air conditioning system. There's no user-operated "on/off" switch for the compressor itself.

The A/C compressor is engaged and disengaged *automatically* by the system's control module based on several factors, including:

* A/C switch: When you turn the A/C on (usually a button or dial), the system signals the compressor to engage.

* Engine speed: The compressor might not engage at very low engine speeds to save power.

* Refrigerant pressure: Sensors monitor refrigerant pressure. If pressure is too low or high, the compressor may cycle on and off or remain off to protect the system.

* Ambient temperature: The system might run the compressor more often in hot weather.

In short: You don't "use" the A/C compressor directly. You use the A/C controls in the vehicle's cabin. If the A/C isn't working, the problem is likely with the A/C system itself, not the compressor's operation (though the compressor could be faulty). Troubleshooting would involve checking the refrigerant levels, fuses, belts, and possibly the A/C control system.