Possible Causes of a Noisy Aux Belt:
* Worn Belt: This is the most likely culprit. A cracked, frayed, or glazed belt will squeal, especially when cold or under load (like using the AC). Solution: Replace the belt. This is relatively inexpensive and easy for a mechanic.
* Worn Belt Tensioner or Idler Pulley: These components keep the belt taut. If they're worn, the belt can slip, causing noise. A noisy bearing within the tensioner or pulley is a common cause of squealing. Solution: These usually need to be replaced as a unit.
* Worn or Damaged Pulley(s): Grooves or damage on the pulleys themselves can cause the belt to slip and squeal. Solution: The pulley(s) need to be replaced.
* Contamination: Oil, grease, or other contaminants on the belt can cause slipping and noise. Solution: Clean the belt and pulleys thoroughly. However, if the contamination is due to a leak, you need to find and fix the leak.
* Belt Too Loose or Too Tight: Incorrect tension can lead to noise. Solution: A mechanic can check and adjust the belt tension (though this is usually done automatically by the tensioner).
What to Do:
1. Check the Belt: Visually inspect the belt for cracks, fraying, glazing, or significant wear. If it looks bad, replace it.
2. Listen Carefully: Try to pinpoint the source of the noise. Is it coming directly from the belt itself, or from one of the pulleys or the tensioner? This will help diagnose the problem.
3. Professional Inspection: If you're not comfortable inspecting the belt and pulleys yourself, take your Ford Focus to a mechanic. They can properly diagnose the problem and recommend the necessary repairs. A visual inspection and a short test drive are often all it takes for a professional to determine the cause.
Simply changing the belt *might* fix the issue if it's clearly worn, but if the noise persists after replacement, it points to a more serious underlying problem that requires professional attention. Ignoring it could lead to more significant damage and potentially even belt breakage, which could leave you stranded.
