* Worn fan motor bearings: This is the most common cause. Over time, the bearings inside the fan motor wear down, leading to friction and the characteristic squealing noise. The noise often changes pitch with fan speed. Replacing the entire fan motor is usually the solution.
* Loose or damaged fan blades: While you've checked bolts, ensure the fan blades themselves aren't rubbing against anything – the housing, the motor, or even debris trapped within the fan. Inspect carefully for any bending or damage to the blades.
* Belt tension (if applicable): While less likely to cause a *whistling* squeak, a slipping or overly tight serpentine belt can make noise. Check the belt for cracks, glazing, or significant wear. Improper tension can also lead to bearing issues in related components.
* Electrical issues (less likely): Though you've checked the mechanical, a short or faulty connection in the fan motor's electrical system could be contributing to the noise, though this is less likely to present as a *whistling* squeak.
Troubleshooting Steps:
1. Visual Inspection: Carefully examine the fan motor and its surrounding components. Look for anything rubbing, damaged, or loose. Pay close attention to the fan blades and the motor itself.
2. Lubrication (Temporary, NOT Recommended): Use caution! While some might suggest lubricating the motor bearings with a penetrating oil (like WD-40), this is a temporary fix at best and can attract more dirt and grime, ultimately causing more damage. It's best avoided.
3. Replace the Blower Motor: This is the most likely solution. You can find replacement fan motors relatively inexpensively online or at auto parts stores. Replacing it involves removing the old motor and installing the new one, which might require some mechanical skill. Consult a repair manual or online video tutorials specific to your 2003 Sebring for detailed instructions.
4. Professional Help: If you're uncomfortable working on the car yourself, take it to a qualified mechanic. They can diagnose the problem accurately and perform the necessary repairs.
Important Note: Continuing to run the fan with a bad bearing will likely cause further damage to the motor, potentially leading to a complete failure and leaving you without heat or AC. Addressing this issue sooner rather than later is recommended.
