No, you cannot put R-134a into a HFO-1234yf system; here’s why…

We have received some questions about putting R-134a into HFO-1234yf system and here’s why you should not do that from EPA.

From the 2015 EPA SNAP Final Rule:

For vehicles for which the manufacturer counts air conditioning credits toward its LD GHG compliance, the MVAC systems (or elements of those systems) are considered emission related components as defined in 40 CFR 86.1803. This designation includes

provisions for emission-related warranty, requirements that they operate properly for the specified useful life, as well as tampering restrictions. For example, if a manufacturer claims air conditioning credits for an MVAC system that uses a lower-GWP refrigerant on a particular vehicle as part of the LD GHG program, removing and replacing that refrigerant with any other refrigerant that has a higher GWP, including HFC–134a, would be considered tampering with an emission related component under Title II of the CAA.

If you’re a service professional and not a MACS member yet, you should be!

Become a member and receive a monthly technical newsletter with information like what you’ve just read in this blog post visit for more information.

You can E-mail us at .

To locate a Mobile Air Conditioning Society member repair shop in your area.

Click here to find out more about your car’s mobile A/C and engine cooling system.

Mobile A/C professionals should plan to attend MACS 2017 Training Event and Trade Show, February 15-18 at the Anaheim Marriott in Anaheim, CA.

Click here to see MACS current public training schedule.

The MACS website is located at


About macsworldwide

Mobile Air Conditioning Society (MACS) Worldwide Founded in 1981, MACS is the leading non-profit trade association for the mobile air conditioning, heating and engine cooling system segment of the automotive aftermarket. Since 1991, MACS has assisted more than 600,000 technicians to comply with the 1990 U.S. EPA Clean Air Act requirements for certification in refrigerant recovery and recycling to protect the environment. The Mobile Air Conditioning Society (MACS) Worldwide’s mission is clear and focused--as the recognized global authority on mobile air conditioning and heat transfer industry issues.
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