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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.

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