Air conditioning (NA and NB)
Many NAs and early NBs still have, or once had, R12 air conditioning, and owners have long argued about converting to R134a. This page lists what is sold and what owners reported. Refrigerant work is regulated; it is not a repair guide.
How to read it. Seller descriptions are from their own pages, and owner accounts from Miata.net forum threads, both read on 1 October 2026 and dated below. Owners disagree, and none of it was tested by me. There are no prices on this page.
What is sold
| Seller | What it says it offers | Fits (as stated) |
|---|---|---|
| RSpeed | an R12 to R134a fitting conversion kit: low-side elbow adapter (which it says lets you service the system without interfering with the intake manifold), high-side adapter and caps. It strongly suggests replacing the receiver drier and having the system evacuated and recharged by a trained technician | 1990-93 NA |
| Moss Miata | a new (not rebuilt) A/C compressor, no core required, 12-month warranty; the brand and refrigerant are not stated on the page | 1994-2005, NA and NB |
| Treasure Coast Miata | a used complete A/C system for adding air conditioning to a car without it: controls, evaporator, compressor, condenser and dryer, piping, brackets and hardware. The page does not say the refrigerant or the condition of the parts, and said it was temporarily not available and to ask | 1994-97 NA |
Treasure Coast and MiataSource also list complete A/C kits for other years, and Moss lists a drier and other A/C parts, per search results; I did not open them.
What owners say
From a July 2006 thread on retrofitting an NA (read the first page of two). The thread is nearly 20 years old, and the owners argued, sometimes heatedly:
- Whether to convert. A poster who identified himself as a licensed HVAC engineer said he would never convert an R12 system, that R134a cools less (so a marginal Miata system gets worse), and that leaks must be repaired whichever refrigerant is used. Others said a repaired system holds a charge for years, and that paying a licensed technician was the best answer. Several owners who converted said it worked, with one reporting a cold system in very hot weather.
- What converting needs, per owners. Replace the receiver drier and the expansion valve, flush the old oil and use the right oil (one poster noted ester oil is compatible with mineral oil), renew the O-rings, and evacuate the system under vacuum before charging, which several said is essential for any refrigerant. One poster asked whether the drier's desiccant differs between the two refrigerants; another said new driers are compatible with both.
- The fittings. Posters said the straight fittings from retrofit kits clash with the intake manifold, and that elbow adapters solve it; one said bending the fittings is a bad idea.
- Regulation. Posters discussed EPA certification to work with R12 and reclaiming the old refrigerant rather than venting it. Check the current rules where you live, and use a licensed shop if unsure.
Not covered yet
- Condensers, evaporators and hoses for the NA and NB, and any NC or ND parts.
- Owner accounts since 2006; the thread is old. The ND's cracked cooler pipe is on its own page: cracked A/C cooler pipe.
© 2026 Fischer Interactive LLC. Written for the Ref Sensor app's Miata users. The seller's page is the authority.