Heating Performance Diagnostic
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Heating Performance Diagnostic
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Step
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Action
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Yes
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No
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DEFINITION: Heating system performance.
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1
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Were you sent here from Symptoms or another diagnostic table?
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Go to
Step 2
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Go to
Symptoms - HVAC Systems - Automatic
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2
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2.
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Allow the engine to idle.
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Does the engine reach a normal operating temperature?
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Go to
Step 3
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Go to
Step 9
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3
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2.
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Select the minimum blower speed.
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3.
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Select the warmest temperature setting.
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4.
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Feel the temperature of the inlet and outlet heater hoses at the heater core.
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Does the inlet heater hose feel warmer than the outlet heater hose?
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Go to
Step 7
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Go to
Step 4
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4
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1.
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Install a thermometer into the center I/P PANEL air outlet.
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2.
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Secure a thermometer to the heater core outlet hose.
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3.
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Select the PANEL mode.
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4.
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Select the maximum blower speed.
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5.
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Select the warmest temperature setting.
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6.
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Record the temperature at the following locations:
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•
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The center I/P PANEL air outlet
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•
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The heater core outlet hose
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7.
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Compare the recorded temperatures.
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Are the 2 temperature readings about equal?
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Go to
Step 5
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Go to
Step 6
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5
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1.
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Inspect and repair the following areas of the vehicle for cold air leaks:
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2.
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Perform the necessary repairs.
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Are the repairs complete?
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Go to
Step 10
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-
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6
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2.
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Perform any necessary repairs.
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Are the repairs complete?
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Go to
Step 10
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-
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7
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2.
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Backflush the heater core.
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4.
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Select the FLOOR mode.
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5.
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Select the minimum blower speed.
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6.
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Select the warmest temperature setting.
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7.
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Feel the temperature of the inlet and outlet heater hoses at the heater core.
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Does the inlet heater hose feel warmer than the outlet heater hose?
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Go to
Step 8
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Go to
Step 10
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8
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Replace the heater core. Refer to
Heater Core Replacement
.
Is the repair complete?
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Go to
Step 10
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-
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9
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Repair the low engine temperature concern. Refer to
Engine Fails To Reach Normal Operating Temperature
.
Is the repair complete?
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Go to
Step 10
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-
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10
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Operate the system in order to verify the repair.
Did you find and correct the condition?
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System OK
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Go to
Step 2
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