QuestionHi. I have a '92 miata, automatic, that in the hot summer months here in Florida does not blow cold air from the air conditioner once it is outside. If I start out from in the garage, it is cold but once I park it in the sun to go in a store per say, it never gets cold again. I had my mechanic add some more freon to it last month as he said it wasn't regestering very cold but it is still not icy cold like I would like it and still blows neutral feeling warm air once I am out running errands during the day. Would adding a 3rd fan help like I read you advised the other person in Texas? Or can I buy a new air conditioner that would solve the problem once and for all? Thanks so much and sorry this is so long!
AnswerAll 90-93 Miatas used an R12 refrigerant system. Since 1994 all cars in North America have been equipped with systems that use R134A refrigerant. Your system has/had to be converted to use the R134A refrigerant. Basically that involves the addition of service valves, flushing the system of the mineral based lubricant and replacing that with PEG (synthetic) oil then recharging with the new freon.
Sadly the R134A refrigerant is not as efficient so automatically the systems have about a 20% loss in deliverable capacity. Some of this is due to the nature of the refrigerant and the R12 systems lower capacity condenser. So how to make things better?
First things first, your system may simply be low on charge which is what may have you searching for an answer so a recharge may be your first step.
Once a system ages past 7-8 years the chances of refrigerant loss from o-rings, hoses and seals due to expansion and contraction almost always results in an annual recharging. Annual recharging is not a bad thing in fact it addresses a mainly otherwise neglected serviceable part of your car. Each time the system is evacuated and recharged it cleans moisture and scale from the system and purifies it for extended life and redelivers a measure amount of refrigerant.
Most people never think of the AC until it no longer works. So not necessarily a bad thing.
Secondly, overcoming the smaller condenser. Newer model condensers can be fitted however, hoses with connections and fitting ends must be fabricated to make this possible. It is costly. A simpler solution is to increase the in flow of air to the condenser. Here, we have added to numerous Miatas, a third pusher fan to the front of the condenser. This modification has netted positive results. To accomplish this a more robust power delivery wiring harness and a simple relay control is required. We have created more elaborate fan controls which work even better but the costs increase with the addition of control devices.
By moving more air through the smaller condenser the vent nozzle temperatures have decreased in stop and start traffic situations where the most demand and least efficiency is. It has no measurable effect over 40MPH since forced air at speed overcomes the fans abilities to make a difference. In most climates the problem is not prevalent at highway speed when air flow and refrigerant flow are optimum.
service@miatashop.com
