miata a/c repair: Grassroots Motorsports forum: Grassroots Motorsports Magazine

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June 5, 2009 8:10 a.m. bigbrainonbrad New Reader

My 91 miata's air doesn't work. My friend I bought it from said the system just slowly stopped working. There is no pressure in the system and the compressor doesn't kick on. I would like to repair this as I'm driving this car to deliver pies as my civic needs some fairly expensive repairs.

My first thoughts are to get an o-ring kit and new dryer. After which I can get someone to pull a vacuum on the system and try refilling it with some r12 that I still have (car is a 91). I'm trying to keep this a cheap repair. O-ring kit and dryer shouldn't set me back more than 60 bucks and evacuating the system and hour of shop time. Outside of replacing these things is there anything that I'm missing. I don't know where the leak was, but there are no visible holes in the condenser and the lines aren't oily, so I figure that it is just a slow leak that happens on a nearly 20 year old car. Any other things I should do while I'm digging in the a/c system?
June 5, 2009 10:22 a.m. aircooled SuperDork

The only problem I see with that scenario is that if the o-rings do not fix the leak it the shop will likely see the leak while pulling the vacuum. In which case they will almost certainly not fill it with the r12 (any venting is a violation).
June 5, 2009 11:12 a.m. jeffmx5 New Reader

When the A/C went out on my 1990 Miata I was told that it was the compressor that was leaking.

I replaced the compressor with a junkyard R143a compressor from a '99 and the o-rings for good measure. I was able to pul some vacuum on it (not enough) and filled with R134a - it is not nearly as cold, but bearable for the few times I use it.
June 5, 2009 11:15 a.m. bigbrainonbrad New Reader

Aircooled, that was kind of what I was planning. I'll replace the cheap and easy stuff that is the most likely culprit based on my friend's description of the decline in a/c performance. I've looked it over fairly carefully and there is nothing that I can see is visibly wrong. Based on him saying that the system gradually lost it's ability to cool, there is no pressure in the system what so ever, and my past experiences with a/c work, I think that a quick refreshing with o-rings/gaskets and a new dryer should get me in the ballpark. Worst case I replace those components and there is another leak I need to fix, best case $60 worth of parts and its fixed!
June 5, 2009 12:11 p.m. Clay Reader

If it's a slow leak, I would just fill it with R134A and see how long it lasts. Mine has a slow leak and I just top off the R134A once every 9 months or so. Works great, less work, and cheaper.
June 5, 2009 1:12 p.m. Winston New Reader

Miata A/C repair:

1.) Open latches
2.) Fold down top
June 18, 2009 6:15 p.m. iwanna1974 New Reader

In reply to bigbrainonbrad:

Hello, I had a similar problem with my car and I found a guy who sells a do it yourself guide to auto A/C leak detection and repair for 5.00 bucks. I bought this guide and a 25.00 vacuum pump and did it myself for under $65.00 including the guide, vacuum pump, O-rings and refrigerent. I was quoted $300.00 by the repair shop.....
June 18, 2009 7:19 p.m. jimbob_racing HalfDork

In reply to iwanna1974:

Do you have the info on the guy that you got the guide from? I have a Miata with non working A/C at the moment and it really is useful for defrosting in the rain and in the winter with the hard top on the car.
June 19, 2009 5:20 a.m. foxtrapper SuperDork

Were it my Miata, I would not do as you describe.

If the system has any charge at all, I'd simply recharge the system and get it working. If it leaks down a can a year, that's cheap. Far cheaper than the seak kit and work involved.

If it has no charge, I'd prefer to pull a vacuum first, but lack of a pump wouldn't preclude me from trying just recharging at this point. Just because a system has leaked down to nothing does not mean air has infiltrated it. The air has to have a reason to get into the system. lack of pressure does not inherently cause air to enter it.