Document ID# 670721
2001 Oldsmobile Silhouette
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Heating Performance Diagnostic

Step
Action
Yes
No

1
Were you sent here from Too Cold in Vehicle ?
Go to Step 2
Go to Too Cold in Vehicle in Manual HVAC Systems

2
Inspect the heating and cooling system for the following:
Low coolant level
Loose or worn accessory drive belt
Leaking or kinked heater hoses
Leaking or kinked radiator hoses
Missing radiator filler cap pressure seal
Improper radiator filler cap operation.
Refer to Loss of Coolant in Engine Cooling.
Perform the necessary repairs.
Are the repairs complete?
Go to Step 3
--

3
Start the engine and allow the engine to idle in PARK.

Does the engine reach normal operating temperature?
Go to Step 4
Go to Engine Fails To Reach Normal Operating Temperature in Engine Cooling

4
Inspect the heater output temperature.

Move the vehicle outdoors.
Ensure that the vehicle hood, doors and windows are closed.
Accurately measure the ambient air temperature.
Allow the engine to warm to operating temperature. (Allow approximately 20
minutes for thorough warm-up.)
Install a precision thermometer into the I/P center air outlet.
Select the VENT mode.
Select the maximum high blower speed.
Select the maximum heat setting.
Measure and record the temperature of the delivered air (heater output
temperature) once the temperature stabilizes.
Compare the temperature of the delivered air (heater output temperature) @
the appropriate outdoor air temperature, to those listed:
49°C (120°F) @ -18°C (0°F)
57°C (135°F) @ 0°C (32°F)
60°C (140°F) @ 10°C (50°F)
Is the delivered air temperature (heater output temperature) within the
acceptable values?
Go to Step 5
Go to Step 6

5
Inspect the following areas of the vehicle for cold air leaks:
Cowl
Air inlet valve
HVAC module case
Make any necessary repairs.
Are the repairs complete?
Go to Step 12
--

6
Start the engine and allow to idle.
Select the HEAT mode.
Select the lowest blower speed.
Select the maximum heat setting.
Feel the temperature of the heater inlet and outlet hoses. (The air
temperature around the hoses must be at least 24°C (85°F).
Does the heater inlet hose feel warm and the heater outlet hose feel cold?
Go to Step 10
Go to Step 7

7
Inspect the thermostat for proper installation and seating. Refer to
Thermostat Replacement in Engine Cooling.

Is the thermostat installed and seated properly?
Go to Step 9
Go to Step 8

8
Reinstall the thermostat correctly. Refer to Thermostat Replacement in
Engine Cooling.

Is the repair complete?
Go to Step 6
--

9
Install a new thermostat. Refer to Thermostat Replacement in Engine Cooling.

Is the repair complete?
Go to Step 12
--

10
Backflush the heater core.
Drain and replace the coolant. Refer to Draining and Filling Cooling System
in Engine Cooling.
Start the engine and allow to idle.
Select the HEAT mode.
Select the lowest blower speed.
Select the maximum heat setting.
Feel the temperature of the heater inlet and outlet hoses. (The air
temperature around the hoses must be at least 24°C (85°F).
Do both the heater inlet hose and the heater outlet hose feel warm?
Go to Step 12
Go to Step 11

11
Replace the heater core. Refer to Heater Core Replacement .

Is the repair complete?
Go to Step 12
--

12
Install components or connectors which were removed or disconnected.

Operate the system in order to verify the repair.

Did you correct the condition?
System OK
Go to Symptoms - HVAC Systems - Manual in Manual HVAC Systems