GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1998 🢒 Prizm 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 HVAC System Check

Step

Action

Normal Result(s)

Abnormal Result(s)*

Vehicles equipped with air conditioning (A/C) have 2 fan motors. The main fan motor is mounted on the left side of the radiator/condenser assembly and the auxiliary fan motor is mounted on the right side of the radiator/condenser assembly. The fans run at low speed (series configuration) when the A/C is operating and the engine coolant temperature is below 83°C (181°F). The fans run at high speed (parallel configuration) when the engine coolant temperature is above 93°C (199°F).

1
  1. Start the engine.
  2. Move the blower speed selector switch from OFF to the following positions in the following order:
    3. 2.1. LOW
    2.2. MEDIUM 1
    2.3. MEDIUM 2
    2.4. HIGH
    2.5. OFF

The blower motor speed increases when the blower speed selector switch is moved towards the HIGH position and then decreases when the blower speed selector switch is moved towards the LOW position.
    •  Blower Motor Always On

2
    • Engine idling until operating temperature is reached.
    • Move the mode control to the HEAT position.
    • Move the temperature control to the hottest position.
    • Move the blower speed selector switch to any position except OFF.
    • Heated air is delivered to the passenger compartment.
    • Most of the heated air is delivered through the floor outlets with some air delivered to the windshield and side window outlets.
    • The blower motor runs at the selected speed.
    •  Heating Insufficient
    •  Heat Excessive
    •  Air Delivery Improper
    • Noise Diagnosis - Blower Motor
    • Noise Diagnosis - A/C System

3
    • Engine still idling.
    • Move the mode control to the DEFROST position.
    • Move the temperature control to the hottest position.
    • Move the blower speed selector switch to any position except OFF.
    • Heated air is delivered to the passenger compartment.
    • Most of the heated air is delivered to the windshield with some air delivered to the side window outlets.
    • The blower motor runs at the selected speed.
    • Defrosting Insufficient
    •  Heat Excessive
    •  Air Delivery Improper
    • Noise Diagnosis - Blower Motor
    • Noise Diagnosis - A/C System

4
    • Engine still idling.
    • Move the blower speed selector switch to any position except OFF.
    • Move the temperature control to the coldest position.
    • Depress the A/C switch to the ON position.
    • The blower motor runs at the selected speed.
    • The A/C compressor clutch engages.
    • Cold air is delivered to the passenger compartment.
    • The main and auxiliary fan motors run at low speed.
    • The main and auxiliary fan motors run at high speed once the engine coolant temperature reaches 93°C (199°F).
    • The main and auxiliary fan motors run at high speed if the A/C system pressure exceeds 1520 kPa (220 psi).
    • Odor Diagnosis
    • System Performance Test
    • VDOT A/C System Diagnosis
    • Noise Diagnosis - A/C System

5
    • Move the blower speed selector switch to OFF.
    • Depress the A/C switch to the OFF position.
    • The blower motor stops.
    • The A/C compressor clutch disengages.
    • The main and auxiliary fan motors stop once the engine coolant temperature drops to 83°C (181°F).
    • Condenser Fan On at All Times

* Refer to the appropriate symptom diagnostic table for the applicable abnormal result.