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How much AC oil to add when replacing components

Learn how much AC oil to add when replacing AC components or refilling the system

Anytime you replace an air conditioning component, you must add more oil. Also, anytime you evacuate the system, you must add more oil to replace the lost oil. This article shows how much ac oil to add when you replace an AC component or refill the system

Oil to add if you replace the condenser, accumulator, receiver, or the evaporator

Add the correct oil to the component before installing it into the system.

ComponentAmount of oil to add
Condenser1 Oz.
Evaporator1.5-2 Oz.
Accumulator2 Oz.
Receiver/Dryer1 Oz.
Hose1 Oz.

How much oil to ad How much oil to add when replacing an AC compressor

Most new AC compressors are filled with enough oil for the entire system. If you’re replacing all the components in your AC system or you’ve flushed the entire system, just install the new compressor and you’ll get good-to-go.

However, if you’re just replacing the compressor, you must remove some oil before installing it, or the system will have too much oil. Here’s how to adjust the oil in the compressor.

1) Remove the drain plug from the old compressor and drain all the oil into a measuring cup.
2) Note how much oil came out of the old compressor.
3) Now, drain all the oil out of the new compressor into a clean cup.
4) Add back in the amount of oil you recovered from the old compressor.

Example: You drained 3.5 ounces out of the old compressor and 6 ounces out of the new compressor. Refill the new compressor with 3.5 ounces of the new oil. That will give you the correct oil charge.

This image shows how to drain oil out of the old compressor, measure it so you can determine how much new oil to add to the new compressor.

Use the recommended oil

Car and truck AC systems rely on circulating oil to lubricate the compressor. But just like engine oil, not all manufacturers recommend the same viscosity AC oil for their systems. For example, for R-134a refrigerants, there are many different viscosities: PAG 46, PAG 100, PAG 150. A Sanden SD7H15 compressor requires SP-15 PAG oil. Sanden SD5H requires SP-20. Sanden compressors used in GM, Honda, and VW models specify SP-10.

Don’t add too much AC oil

Every time you lose refrigerant, you also lose some AC oil. So, it’s common for DIYers to go overboard and add more oil every time they add refrigerant. But that can be self-defeating. Too much oil decreases cooling because it coats the interior fins and blocks heat transfer.

When a shop evacuates an AC system, they measure the amount of oil that comes out, and they replace it with the same amount. But how are you supposed to know? Yeah, it’s a crap shoot if you’ve lost refrigerant due to a leak. The general rule is to add 1-Oz. if the system has lost just a few ounces of refrigerant. However, if you’ve lost more than that, the best approach is to evacuate the system, flush it, empty the compressor and then add full charge of oil

What happens if there’s too little oil in the system?

AC compressors must be lubricated from the crankcase and the top of the piston. The refrigerant carries oil through the system to ensure there’s always oil mist entering the compressor along with the refrigerant vapor.

If there’s a leak, you’ve lost oil, and that lack of oil will wear out the compressor. That’s why it’s always best to evacuate the system, flush it drain the compressor and add back in the full oil charge instead of guessing

©, 2015 Rick Muscoplat

Posted on by Rick Muscoplat

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