1. Check the Vacuum System:
* Locate the Vacuum Lines: Start by tracing the vacuum lines coming from the engine compartment into the HVAC system under the dash. These are usually thin, flexible plastic or rubber tubes. Look for cracks, holes, loose connections, or areas where the lines have come off their fittings. Pay close attention to the lines near the HVAC control unit itself.
* Listen for Hisses: With the engine running, carefully listen near the vacuum lines for hissing sounds, indicating a leak. Spray a small amount of soapy water (a solution of water and dish soap) on the lines and connections. Bubbles will appear where there's a leak.
* Test Vacuum Actuators: You'll likely find several small vacuum actuators connected to the blend doors. These are usually plastic devices with a diaphragm. Some may be accessible under the dash; others might require partial disassembly. If you can access them:
* Manually check for movement: Gently try to move the actuator lever by hand. If it moves freely, the actuator itself is likely fine. If it's stiff or doesn't move, the actuator may be faulty.
* Check for vacuum: With the engine running, carefully check if vacuum is reaching the actuators. If you have a vacuum gauge, use it to check for proper vacuum at each actuator. If not, you need to trace the lines back to identify leaks.
* Check the Vacuum Reservoir (if equipped): Some vehicles have a small vacuum reservoir. This stores vacuum to help ensure smooth operation of the HVAC system. Check this reservoir for cracks or leaks.
2. Check the HVAC Control Unit:
* The Mode Selector: The problem *could* be within the control unit itself, although this is less likely than a vacuum leak. The mode selector switch (the part you use to change where the air blows) might be faulty, preventing it from sending the correct vacuum signals to the actuators. This would require disassembly and inspection or replacement of the control unit.
3. Troubleshooting Steps:
1. Start with the easiest: Begin by visually inspecting all vacuum lines for obvious damage. Repair or replace any damaged lines.
2. The soapy water test: This is crucial for finding subtle leaks.
3. Isolate the problem: If you find a leak, repair it and see if the problem is solved. If not, move to the next potential problem area.
4. Actuator test: Test actuator movement. A bad actuator will need replacement.
5. Consider the control unit: If all vacuum lines and actuators are good, the problem likely lies within the HVAC control unit. This is a more involved repair, requiring specialized knowledge and tools. Replacement is often the solution.
Important Notes:
* Safety First: Disconnect the negative battery terminal before working on the electrical system. Always exercise caution when working under the dashboard.
* Vacuum Diagrams: A repair manual or online service manual for your 1996 Sebring will be invaluable. It will show you the vacuum line routing and the location of the various actuators. Finding such a diagram is highly recommended.
* Professional Help: If you're not comfortable working on your car's HVAC system, it's best to take it to a qualified mechanic. This can be a complex system, and improper repair could lead to further problems.
By systematically checking these areas, you should be able to pinpoint the source of the vacuum leak and get your air conditioning back to working correctly. Remember that patience and a methodical approach are key.
