Refrigerant Type: R134a
Ambient Temp: 45F
Country of Origin: United States
My son had his 1992 Civic converted to R134a a year ago October by the Honda dealer. By the mid summer the system was out of refrigerant and I was not able to top off. So I took it to a shop today to have other issues repaired that I cannot do at home, and asked them to find the AC leak, repair, and recharge. They said they could not get a reliable manifold reading in the colder air we have at this time of the year. Its in the mid 40's today. They recommended I bring it back in late March. I've never heard of this before with the weather affecting the repair of an AC system. What is the truth regarding this issue with the weather, true or hogwash?
It's a conversion. So no proper charge capacity will be listed. They will use guage readings to help determine the proper level. Cold temps make it harder to get a true reading.
First place to look for a leak on a scroll application is the compressor discharge fitting o-ring (& condenser inlet o-ring). Due to the scroll characteristic very high temperature gas temp, the high spec R-12 OEM o-ring just barely survives with R-12. R-134a reaches a even higher discharge temp at high rpm, Therefore the OEM R-134a o-ring from future OEM R-134a models is best. Under some low charge conditions the discharge gas temperature becomes abnormally high and trips the TPS/thermal protection switch (which resets it's self when it cools).
OEMs publish their R-134a retrofit charge recommendations. approximate charge (in cold ambient) for a R-134a retrofit is 86% of R-12 OEM charge. This is based on a large variety of car tests for optimum charge (SH % SC) and agrees closely with the respective molecular weights of the respective refrigerants. Always consider the charging hoses retained refrigerant when figuring charge amount.
Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
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Best way to top off these old Honda's was using the sight glass, but even at that, could only do that with R-12, and an ambient temperature of of at least 80*F. Weren't that good either with AC, in particular if this car is the hatchback with a dark color, was like Dr. Who's telephone booth, much larger on the inside than the outside.
As ice-n-tropics stated, evaporator block was a problem in these cars, didn't have that problem in the 80's, was Honda's answer to the dollar devaluation against the yen, really had to cheapen up their cars to be competitive in the US market.
You will never get a clear sight glass, meaning you are firing the evaporator with a solid liquid with R-134a. While its pressure is only about 10% higher at cooler temperatures, its rate of pressure increases is far greater once the ambient exceeds around 80*F. So to keep the high end from blowing its cork, you have to attempt to cool with foam. And foam doesn't cool very well. These cars really need a parallel flow condenser and improved air cooling that, that small alternator has problems keeping up with. If those components are still good, far cheaper to stick with R-12.
Just wonder how you are justifying your repairs on this thing, could barely justify buying the parts from Honda dealers and doing the work myself. No set retail value on parts, did find a Honda dealer that required a 400 mile round trip that was making when the price of gas was cheap. Local dealers were outrageous. Was in that era, where my entire family was driving Honda's, we quit and went domestic. In regards to unibody rust, were just as bad as the domestic cars back then. You must be in a salt free area.
No sight glass after 1991. I think the 1992 has the same parallel flow condenser as the later factory 134a models, but it is a small condenser and small system overall.
The main way to find leaks in cold weather is a static test with an electronic leak detector. If it is a big enough leak to have leaked down to zero pressure, that should find it. If nothing obvious turns up, the next step is to install UV dye and use the car with the A/C on for a week or so, then come back and look for dye marks. Dye only works with the system charged up and running, so you must wait for warm weather.
There are two or 3 Honda dealers online that sell genuine parts for about 40% off of list. Last time I needed a GM part from a dealer it wasn't cheap either. The major parts of the A/C system are readily available aftermarket.
Edited: Mon January 02, 2012 at 8:24 AM by mk378
Is my memory getting that bad? Seen plenty of aftermarket receivers without the sight glass, but recall the original Honda's did have them. And this one was converted, so no telling what they put on there. Maybe they didn't even change it to an R-134a type like they were suppose to.
No siteglass on a 92 Civic.
Okay, goodbye to a very useful tool for determining state of charge, on a 80*F, could just fill it leaving a bubble or two, check it in a couple weeks, also on an 80*F day at the same 2,000 rpm engine speed to learn in a second if any more bubbles are appearing. Know instantly if you have a leak.
GM also use to use a sight glass, not only for the refrigerant, but for the oil level in the compressor, but got rid of that in the early 60's. Still can get an accurate reading with gauges for the refrigerant, but dead meat with the oil.
Maybe my nephews Honda was a 91, ha, use to brag about having a photographic memory, but think its way over exposed.
All these people want to change over to 134a because "Joe" their mechanic told them it's better or it's illegal to recharge with R-12 or the government won't let us do that. All baloney ! Your system was designed for R-12, it works more efficiently with R-12, you have the exact spec of how much R-12 to put in your system to make it work right, and it's cheaper to keep it R-12. So, why pay your mechanic to install expensive parts that you don't need and run a grandiose experiment guessing how much 134a to use. There is usually no reason not to keep it R-12. End of story.
Getting tired of hearing my congressman or senator telling me there is a war going on in Iraq or Afghanistan augmented with economical issues. To simply ask the question, why R-12 has been banned or highly restricted. Not one bit of evidence has supported the theory that CFC's were depleting the ozone layer, even NASA backed out of this. But got started by some crook by the name of Al Gore.
Still enjoy these older vehicles with a sense of freedom that big brother is not constantly spying on me, two administrations later, still no reverse on this ridiculous mandate. Now using propane in spray cans, but haven't heard too much about that danger. But ironically the EPA is super against using any form of HC's in AC systems.
What a world of contradictions we have to live in. And those R-134a ports are just about the worse design they could have come up with. Doing this AC stuff for 48 years now, refrigerant leakage has never been as bad as it is now since the EPA got involved.
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