How often to service A/C refrigerant?

A good ac system with an electric compressor often has no loss because the traditional pulley shaft seal does not exist. So coil leaks are more likely, evaporator due to wet coils and condensers due to road debris.

Same goes for residential ac's, a hermetically sealed electric compressor with common evaporator leaks.

With that said, a slow automotive leak rate is worth a gas and go unless it has been opened to the atmosphere or has leaked down completely. In those cases a good vacuum at a minimum how followed by a leak search and refill if appropriate.

 

Yeah ever noticed when you open your system you take the low side gray cap off of that hose in between the transmission. You hear the little whoosh noise imagine how ... The Schrader of thats what the big things are called . You can buy the inserts and change them

 

How did you get such an accurate measurement of refrigerant? Do you have a machine that evacuates and measures? Looks like you're well aware that refrigerent amount is not based on pressure because its a variable pressure system and I'm curious as to your methods. Maybe you've found a way to do it without the expensive machine that evacuates and weighs it?

 

There's a blurb in the repair manual AC section that describes checking for bubbles in the sight glass. It's good to have a person in the car and you looking at the sight glass with a flashlight as the AC is started so you can see how the bubble formation/collapse sequence looks. It's very easy to tell if charge is low.

 

Most refrigerant people have scales now and they're weighing out of cylinders like I use a 25 lb cylinder of 134a or Enviro Temp so I can meter out 1.. 0 pounds and so on . But rarely do I just buy 2 cans pull vac verify . Drop 1 can . Conn second . And put a few squirts looking at glass . 8 get the bubbles to do right . Make sure is almost freezing . Close it up.

 

A 2nd gen can go a long time without loosing refrigerant. Mine has been 14 years since it was filled after the condenser was damaged.

There is a pressure sensor that detects when the refrigerant is too low and keeps the system from turning on, so it can't be damaged from being low.

 

A professional machine has the R134 tank on a scale. To get an real accurate fill you first remove/recover all the R134 from the system and weigh it. This tells an honest shop how much is needed so they can charge the correct amount, it can also help diagnosis, for instance if it's overcharged which can cause poor performance. Then they add the factory specified amount by weight. The sight glass bubbles is a ball park indication, it's not exact.

The R134 is recycled/reused, the recover tank is the fill tank, so they should only charge you what they have to add to the amount they initially recover to get to the correct total amount.

It gets technical because there are 2 different compressor oils, so a big shop will have 2 machines so the oils don't get mixed.

 

My 2007 has 18 years without any loss in AC performance... Greatest car ever!

 

This is a valid concern on the real oldsters. Not usually worth doing anything about them until you have a significant leak event. It is absolutely worth replacing the o-rings & valves on a 10+ year old car as a "while you're in there."

 

If it's not full and they recover the refrigerant and weigh it . They know what they've taken out. When they go to put it back in they dial in what's called for on yellow sticker.

 

A sight glass charge is only good at that ambient temp with that cabin load. It can ensure there is a minimum amount in the system. Higher outside temps and cabin loads can result in lower performance when the txv does not have enough liquid to regulate superheat.

Too much refrigerant increases pressures, decreases efficiency and a significant excess can cause a high pressure shutdown.

Weighing it in is the correct method and simply requires an accurate scale with ounce resolution.

 

I

Seems not that useful, the attached "inspection" pdf, says if you see any bubbles it's undercharged, and if you see nothing it could be good, overcharged or empty:



I'd get it checked by pros, preferably dealership, when the cooling performance falls off.

 

With a sight glass you can see the refrigerant moving even when it's full. It does not mean it's right in a critically charged Prius with minimal refrigerant requirements and a variable capacity compressor.

Typical residential and light commercial systems don't have sight glasses as a cost saving measure. However most of them can be topped off by calculating superheat and or subcooling using refrigerant pressure and temperature gauges.

98% of the time low refrigerant causing low performance is easily diagnosed with a sight glass in the liquid line. Most sight glasses can identify moisture by a change of color. So there are reasons Toyota includes sight glasses.

I put sight glasses on my residential systems for those reasons.

Buying a refrigerant scale and vacuum pump is far less money than an automotive shop's all in one system. A nice feature of a shop system is it will shutoff charging by itself and it makes recovery and vacuum procedures easier to do without error.

Getting certified to handle refrigerant is not that difficult if you take a one day class offered by universities and supply houses. Basically it allows you to buy from supply houses and gives you key understandings of various refrigeration systems if you get the Universal EPA license. Which I did for my own purposes, not as a business.