A/C refill with a refill kit?

What makes you think it needs a refill?

The AC is one system in the Prius that I would let the dealer deal with.

 

concur.^

 

The Prius uses the same R134A refrigerant that all other cars use, but the lubricant is ND11, which is for electrically driven compressors that need better high voltage insulation. ND11 is not compatible with other oils. The pro shops need to have separate equipment for ND11 to avoid cross contamination.

The need to top up the system implies a leak, so that is best fixed first. Unlike the conventional belt driven compressors, the Prius system is hermetically sealed and won't leak unless there is damage. I would second the above advice and leave it to the pro's.

 

Hi Steven, below is my response to a similar question from this thread: Recharging my A/C?
Also click on the link above to see other relevant comments and links in that thread.

Also, I forgot to mention that the lower portion of the condenser is actually a subcooler. So when filling with refrigerant, an additional 100g must be added after bubbles disappear in the sight glass.
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If you are topping off refrigerant, this option might be better;

 

Just like to add to the "take it to the pros" chorus. The typical reason for needing a recharge is a leak. And AC leaks should be addressed, not patched with top ups.

And to add to the other chorus, do even need a top up?

 

Here is also an old technical presentation from Toyota for the HVAC geeks:
http://www.sae.org/events/aars/presentations/2004-ishikawa.pdf

 

There is no such thing as a "perfect seal." All seals leak a little over the years. NASA uses the most expensive and highest tech seals, but the still leak.

Unless there is a significant leak down to near zero, there is no harm in "topping off" an AC system.

 

Prius (gen2 and after) ac-system has no seals that have to seal against moving parts. Normal ac-system has compressor front seal (it seals against spinning shaft) where almost all acceptable leaking comes from. In Prius (gen2 and after) only acceptable leaking comes from seals where seal has to move when temperature changes. So acceptable leaking in Prius ac-system (gen2 and after) is small fraction of acceptable leaking in normal ac-system.

 

I've worked on auto air for over 45 years. The shaft seal doesn't spin on the shaft. It is the end of a spring loaded ring impinging on a plate.

No seals? Maybe no "spinning seals," but no gaskets and "o" rings? ALL gasket and "o" rings "weep." Maybe, so little, it will take years for it to be detected.

So, a "top off" after eight years is normal.

 

You are both correct. But I would like to expand and quantify your statements:

There is no harm in "topping off" an AC system, if:
- it is so low on refrigerant that performance would significantly benefit from a top-up.
- it is done properly.

Topping off a system that doesn't really need it does harm by wasting money, time, material, and unnecessarily risking that something could go wrong.
Doing it properly means using equipment uncontaminated by oil from other systems, purging and evacuating lines to prevent contamination from air and moisture, and filling to within 30 grams of the specified optimum level. Can this be done reliably by an amateur with a refill kit?

I will venture to guess that the Prius system looses about 1 to 2 grams of refrigerant per year. There is a window of good performance within +/- 30 grams of optimum charge. Assuming that, on average, systems are charged close to the optimum at the factory, then it would typically be about 15 to 30 years before there would be a significant benefit from topping off the refrigerant.
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Like I discovered in the transaxle fluid level, the fill at the factory is just about 10ml above the low fill level.

The AC systems are fill just a tad above the minimum fill level with enough to spare for very minor leaks during the 36 month warranty period.

Given the number of cars produce, filling the systems to optimum level or to fill the system to the top level is not in the interest of the manufacturer. It saves them a lot of money.

A six ounce top off in three years is actually a GOOD option. I did that to my 1998 Mazda MPV. The AC still functions like a NEW system 16 years later.

 

To do it accurately, don't you need to evacuate the system first and then refill?