Troubleshooting by Symptom
Poor Heater System Performance
CAUTION
Check all fluid levels and adjust as needed, before operating vehicle for extended periods
at idle.
1. Start the engine.
2. Idle the engine until the thermostat opens (upper radiator hose will be hot) Is the
engine at normal operating temperature (approx. 200° F)? If yes, go to the next
step. If no, go to step 16.
3. Set the mode selector to FLOOR mode.
4. Set the heater control selector to the warmest temperature setting.
5. Set the blower speed the lowest setting.
6. Carefully feel the inlet and outlet heater hoses at the heater core. Is the inlet heater
hose significantly hotter than the outlet heater hose? If yes, go to step 14. If no, go
to the next step.
7. Set the mode selector to PANEL mode.
8. Select the maximum blower speed.
9. Select the warmest temperature setting.
10. Place a thermometer into the center I/P PANEL air outlet and affix a second
thermometer to the heater core outlet heater hose.
11. Record the temperature at the center I/P PANEL air outlet and at the heater core
outlet heater hose. Are the two temperature readings about equal? If yes, go to the
next step. If no, go to step 13.
12. Inspect and repair the cowl, cowl area, recirculation door, and the HVAC
evaporator/heater core case for cold air leaks. Repair any problems found, go to
step 17.
13. Inspect the temperature door operation. Repair any problems found, go to step 17.
14. Turn OFF the engine. Back-flush the heater core. Start the engine. Select the
FLOOR mode and the lowest blower speed. Select the warmest temperature
setting. Feel the temperature of the inlet and outlet heater hoses at the heater core.
Is the inlet heater hose feel significantly hotter than the outlet heater hose? If yes,
go to the next step. If no, go to step 17.
15. Replace the heater core. When the repair is completed, go to step 17.
16. Check for low engine temperature problems, Repair or replace as needed, go to
step 17.
17. Operate the system in order to verify the repair. If the system operates properly,
the repair is complete. If the heater still does not work properly, repeat the entire
procedure.
Summary of Contents for TrailBlazer
Page 1: ......
Page 26: ...Fig 3 Typical body and undervehicle maintenance locations Refer to chart for descriptions ...
Page 29: ......
Page 30: ......
Page 31: ......
Page 175: ...Spring free length check Valve spring squareness check ...
Page 192: ...Front of piston mark ...
Page 361: ...5 3L Engine Except Saab Underhood Fuse Block 2003 2005 Early Production ...
Page 469: ...Removing the outer band from the CV boot Removing the inner band from the CV boot ...
Page 470: ...Removing the CV boot from the joint housing Clean the CV joint housing prior to removing boot ...
Page 471: ...Removing the CV joint housing assembly Removing the CV joint ...
Page 472: ...Inspecting the CV joint housing Removing the CV joint outer snap ring ...
Page 473: ...Checking the CV joint snap ring for wear CV joint snap ring typical ...
Page 474: ...Removing the CV joint assembly Removing the CV joint inner snap ring ...
Page 475: ...Installing the CV joint assembly typical ...
Page 553: ...9 Torque the lug nuts to specification 10 Lower the vehicle ...
Page 556: ...Toe in Frame Misalignment Frame misalignment ...
Page 588: ...Bleeding caliper ...
Page 624: ...Manifold gauge set components Refrigerant recovery recycling station ...
Page 676: ...A C Specifications ...
Page 677: ......