I enjoy helping people learn how to work on their own vehicle. Noises are one item people always are concerned about when they come from their own vehicle. Isolating the noise can sometimes be difficult. But there are a few tricks of the trade that can help to locate the component that is making the unwanted noise.
A couple of weeks ago a close friend called me and said she can hear a squealing noise coming from her engine when she turns on the air conditioner (AC). I told her to bring it by the house one evening and I would show her how to isolate the noise and then repair it.
This was exciting for her because she loves getting her hands dirty and learning new things that will save her money. When she got to my house she turned on the AC system and sure enough a squealing noise was present. While the vehicle was running I was very careful to show how you isolated the noise. The noise would come on and off with the cycling of the AC compressor. (Be very careful of all moving parts and do not have loose clothing or hair, for it could get caught in the moving components) Using a large handle screwdriver I put it on the compressor and then my ear to the handle of the screwdriver. The noise was defiantly coming from the compressor. I showed here how to do this then she repeated the task.
She ask what a good one sounded like so I started my car and turned on the AC and allowed her to listen. The sound was completely different. When a compressor clutch starts to go bad is can make a squealing noise because the clutch can not grab and lock up with the compressor while the pulley is being turned by the engine.
She ordered the parts and had a local shop evacuate the refrigerant from the system. I recommend this instead of just letting the refrigerant go into the air (the Clean Air Act of 1990 has many regulations on this). Once the compressor got in I walked her through the manual on how to replace and what steps to take to be sure the job was done correctly. Once the new compressor was installed she went back to the same shop and had them oil and recharge the AC system. They also tested the operation and the compressor replacement fixed the noise.
Success done by process.
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