Question: I have a Mackinac model that was built in 2002 with a York air conditioner. We moved into it in 2005. Twice when I have had the AC annual checkup done (I have it done every two years), I have been told by the repairman that I need to replace a rusted capacitor 40/50MFD-370V at around $130 each time. Has this been the normal practice for this type of AC or have I been taken to the cleaners each time? I was told by the repairman that if the rusty thing was not replaced, it might explode – wrecking the entire air conditioner. I have kept the last one they replaced, which was rusty but looked like it was not in that bad condition. The first repairman was from [company A], and the last one was from [company B].
Answer: The capacitor in your air conditioning unit is there to help start the compressor motor. It gives a power jolt to the motor to get it started. These capacitors are usually 35 – 50 microfarads. If that value drops to 25 – 20 microfarads, it is a sign that it is failing and should be replaced. If the capacitor fails, the compressor motor may not start. If it does not start, it will continue to draw power, causing it to heat up. There is a thermal overload device in the motor that will cycle the power off when it gets to a preset temperature. When it cools down, it will switch the power back on and heat the motor again. It will cycle like this until you finally notice that the air conditioner is not coming on and call a service technician. This thermal cycling is not good for the motor and may burn it out.
The service man telling you that the capacitor “might explode wrecking the entire air conditioner” is either incompetence on his part or a lie to get you to pay for a repair. The only way to know if a capacitor is going bad is to measure the capacitance with a meter. Rust has almost nothing to do with the condition of a capacitor. The shell of these capacitors is usually galvanized steel, and a light coating of rust, as yours had, is nothing to worry about.
Now let’s take a look at the cost. If you Google a “40 mfd 370V capacitor for air conditioner,” you will find they cost $10 to about $23. If the service technician measures the capacitance and confirms that the capacitor is in fact bad, it would be fair to charge you $20 to $40 for the part. If this problem is discovered during a scheduled maintenance check, the labor you have paid for in this check should cover this five-minute job. The $130 you paid is way out of line.
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