How do I calculate the A/C compressor compression ratio?

Add atmospheric pressure to both high and low gauge readings, then divide high side by low side. A good range is 6.5:1 to 7.5:1.

What are signs my A/C compressor is going bad?

Growling noise, inconsistent cooling, hot discharge line and cold suction line imbalances can indicate compressor damage.

Can Auto A/C Repair LLC diagnose my A/C compressor on-site?

Yes! We provide mobile diagnostics and A/C repair throughout Miami-Dade County. Call us for a same-day estimate.

How long is my car A/C compressor going to last?

TL;DR: Check Your A/C Compressor with Compression Ratio

To test if your A/C compressor is working, compare high- and low-side pressures using a gauge set and calculate the compression ratio. A healthy system shows a ratio of 6.5:1 to 7.5:1. Auto A/C Repair LLC offers mobile compressor diagnostics and replacement in Miami-Dade County. Call (786) 483-9406 to schedule a same-day inspection.

How to Test Your Car A/C Compressor

Professional Guide by Auto A/C Repair LLC

A/C Compressor Test: Compression Ratio Test

The A/C compressor is considered the heart of the refrigeration system. The term that best describes a compressor is a vapor pump because it increases the suction pressure level to the discharge pressure level. Compression ratio is the technical expression for pressure difference; it is the high-side absolute pressure divided by the low-side absolute pressure. Absolute pressures rather than gauge pressures are used when figuring compression ratio in order to keep the calculated compression ratio from becoming a negative number. To check A/C compressor compression ratio, note on paper the low and high side gauge readings and add atmospheric pressure to both readings. Divide the high side reading (with the atmospheric pressure added) by the low side reading (with the atmospheric pressure added). A proper compression ratio should be between 6.5:1 and 7.5:1. A ratio of 8:1 or higher may indicate a failing compressor. If your car’s A/C system has out-of-range values, contact us now for expert diagnostics.

Understanding the A/C Compressor Compression Ratio Results

When compression ratios are high, the compressor’s discharge temperature will also be elevated. This is because of the higher heat of compression during the compression stroke. Excess heat can degrade lubricating oil, creating acid in the system and leading to compressor failure.

How Do I Know If My Compressor is Bad?

By Sound:

Growling noise when disengaged: Possible worn pulley bearing
Growling noise when engaged: Internal compressor damage

By Temperature:

Identify the A/C compressor under the hood of your car.
The suction line should be cold after 5 minutes of operation.
The discharge line should be hot after 5 minutes.
The compressor itself should be warm but not extremely hot.

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