QuestionQUESTION: 1992 miata mx5 AC problem...1) pretty sure my AC is just low on freon because sometimes it blows a little cold but sometimes it does not blow cold at all.....especially the further I drive the warmer it seems to get, especially on a really hot day...does that sound like a leak or another problem? Would it blow cold at all if the freon was low?
2)Assuming that the freon is the problem, I must convert my R12 system to R 134--- already have the kit. How much should a shop be charging me to take out the old R12? WOuld they do it free? I would like a shop to take out the old R12 so I can use my kit to in new R134---is that as easy as it appears to do that?
Thanks so much
ANSWER: If your system is still original then a couple of age related issues will creep up on you and likely are the source of your current problems.
As time passes moisture, scale and particles from the compressor as it wears develop within the system and are normally filtered by the receiver/drier (RD) unit. After years of use the RD unit no longer has the capacity to collect this material and so they pass through the system eventually blocking the smallest passage which is the expansion valve.
Symptoms normally present similar to this; the system cools for about 5-10 minutes then gradually gets warmer for a period. Then eventually returns to cooling and repeats the cycle.
What's happening is the scale if plugging the expansion valve once it blocks off flow the system goes warm. As the compressor cycles off and the high side and low side equalize the scale if pushed back out and so the system returns to some level of cooling. Eventually it will block up and nothing but replacing the expansion valve will solve the problem.
Now if it is a matter of the system cooling and not being able to keep with ambient demand than it could just be a low charge, though considering your age, the afore mentioned is very probable.
Proper course of repair;
New (mazda) receiver/drier and associated o-rings
New expansion valve (no longer available from mazda without the cooling assembly ($$$)
Conversion from R12 to R134a, unavoidable and must be done by a qualified shop facility with a closed loop recovery system. Charging a system without a CLRS will release freon into the atmosphere and will introduce air into the AC system. Additionally, the system must be flushed of ALL mineral oil and replaced with PAG oil. Mineral oil is not compatible with R134.
Note; R134a is about 15% less efficient than R12 so you will not achieve the same cold temperature that the system once did. Adding a third pusher fan to the condenser has helped reduce higher head pressures which results in cooler vent readings.
One last note, AC systems are neglected until they break, get yourself into the habit of having the system evacuated and recharged every 12-15 months. Two things, it filters out scale and compressor debris, replaces lost refrigerant (lost through expansion and contraction of old O-rings and seals), consider it like an oil change, regular maintenance that will extend compressor and expansion valve life.
service@miatashop.com
"If your good at what you do you should be well paid"
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QUESTION: Great tip...was totally unaware..in the future I will have the system checked regularly. Your answer sure does seem to fit with my symptoms. However, I failed to mention in my first email that some of the components of the system have been replaced on 2 occasions (last in 2003)but not the entire system either time......but the shop I went to is closed now and my car repair receipts were stolen when my car got broken into and I can't remember exactly what was repaired ...guess I am looking for reasons to believe that I might be able to get away with just the recharge.
(let's call your "proper course of repair" plan A, and "recharging the system",plan B for this next scenario).
If you were me, would you try plan B first and hope it was a matter of the system not being able to keep up with the ambient demand, as you mentioned? If I tried plan B first and it did not fix the problem...I would still have converted the system and be that far already ( I bought the kit that includes the adaptors and R134). If plan B did not fix the problem, I would go to plan A. Does that sound reasonable?
I realize I still need to find a shop to flush/evacuate the system even if I go with plan A so either way I need to find a good shop. I live in Honolulu---do you have any recommendations on shops that are trustworthy? From my own bad experiences and many of my friends I have major trust issues with AC repair places ( I rate them up there with car salesmen but know they can't all be bad), and that is the reason I am so glad to have a site like this to help sort things out. ..thanks again!!
ANSWER: I hear the phrase, changed the entire system out" a lot. There are obviously shops out there that sell people the bill of goods on swapping out entire systems. The reality of a system is you only need address the issues that present a problem.
With a Miata, usually in this order.
Receiver/Drier
Expansion Valve
Line O-Rings
and one day eventually a Compressor.
Evaporators develop pin holes somethimes
and Condensers get rocks or sticks that poke them sometimes. Other than that the rest is likely to outlast the car.
Sadly you were sold a bill of goods with "the kit". That's not to say you can't convert the system yourself but, not advisable for the long term reliability of the system. R134a and mineral oil (the oil in the R12 system) is not compatible and will sludge inside the system and cause the compressor to fail early. So flushing it clear of this is mandatory. Otherwise a conversion it mainly is the installation of R134a valves. The valves should be 90 degree versions not straight ones since the charge head will not fit otherwise due to the tight spaces around the service fittings.
If you have a digital camera email me pictures of under the hood and I will tell you by looking what may have been done to it. Focus on the passenger side rear and up front before the radiator.
service@miatashop.com
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QUESTION: Is it possible to have an R12 system recharged without doing a conversion---do AC shops still have R12 available or is that not a possibility? I did not think so but I have heard from several people at Firestone, Midas that R12 is still available via AC shops....know I will get the truth from you
AnswerNot likely, the use of the refrigerant was banned in many States starting in 1994 due to EPA regulation, it may exist at some places though use of it is pretty much a thing of the past. I would suspect any shop saying they have R12 is using a synthetic hybrid of it and not actual R12. Names like Freeze12, ES12. They are chargeable into an R12 system though not as efficient and costly. R12 if located is extremely expensive.
What you have to think of is if your away from home and you need your system charged, "can you find an R12 hybrid". You can always find R134a just about anywhere these days but, not R12 stuff.
