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Sanden AC Compressor Diagnosis

Sanden Compressor On-Vehicle Warranty Functional Test Procedure

The AC Compressor is basically a pump that converts the low-pressure liquid refrigerant into a high-pressure gaseous refrigerant. Inside the compressor, a spinning rotor sends the refrigerant under high pressure to the condenser. The compressor is responsible for maintaining the pressure difference between the low-pressure and high-pressure sides of the AC system. The compressor can fail in a number of ways. Sometimes, an AC system stops working for reasons besides the compressor. Here are some ways you can diagnose an AC compressor find out what is wrong with the compressor.

1) Is the compressor rotation smooth?

With the vehicle turned off, rotate the compressor shaft with a 14mm socket to check for smooth rotation. Grinding or hanging during the shaft rotation is caused by the broken components within the compressor.

Yes - Continue with steps 2 through 4; No — Remove the compressor and return for evaluation.

2) Is the field coil receiving greater than 11.5 volts?

This test should be conducted with the engine running and clutch engaged.

Yes — Continue with steps 3 through 4; No — Correct the vehicle electrical system.

3) Is the field coil resistance between 2.8 and 4.4 ohms?

Coil resistance outside of this range will not engage or will cause fused circuits to open.

Yes — Continue with step 4; No — Remove the compressor and return for evaluation.

4) Is the compressor capable of producing 350 psig or more?

Excessive high pressure can be artificially produced by preventing air flow across the condenser, thus minimizing heat removal from the system. This can be best accomplished by disconnecting the fan switch/relay, or simply blocking the condenser with a sheet of cardboard.

Yes — Compressor is functioning, do not remove the compressor; No — Use the flow chart below.

Warranty Procedure    

Note: This is not an official install or instructional guide. Buy Auto Parts is not responsible for any damage or injury that can occur during these procedures.

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Buy Auto Parts is the best place online to get AC compressors at unbeatable prices. We stock a wide range of OEM replacement and aftermarket parts for every make and model. To find the AC compressor for your car, simply tell us your car's year, make and model. Your order will be shipped from the warehouse closest to your location. We offer free shipping for purchases over $99 in the continental United States. Our products have been throughly-tested to meet or exceed industry standards. You can reach us on our support line at or leave us an email at [email protected], if you need help in choosing your part. Please feel free to leave us an online review. We value your feedback!

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