A/C - bubble in sight glass

The spec is for you to set the temp to MAX COLD and turn the fan speed to high. If you see bubbles in the sight glass and you feel the air conditioning is insufficient, then refrigerant should be added until the bubbles go away.

A footnote in the repair manual indicates that if cooling is sufficient and ambient temp is high, then it is OK if bubbles exist. So there's some ambiguity.

If you DIY make sure that you do not use refrigerant that contains compressor oil. Use of regular oil will damage the compressor permanently.

 

You're right; the only thing that belongs in the circuit is pure R134 (in both a gaseous and liquid state. Before turning the ac on, the sight glass has no liquid in it, just gas. When you turn the ac on, the compressor raises the pressure on the condenser side of the system, heat is removed from the gas and the gas condenses into a liquid which then makes its way through the sight glass (that was the bubble you saw) to the evaporator where a metering device feeds the liquid into the evaporator at a reduced pressure and and the liquid starts to boil (at a low temp.) and absorb heat. Next stop is the compressor where the cycle starts all over again.

I understand the correct charge for the prius is less than a pound of R134 and it's critical. The only correct way to charge the system is to evacuate it and weigh in the correct amount. You can't be that exact using the sight glass.

 

Good work koolingit, That was a very accurate and concise explanation of what takes place with the refrigerant in the system.

 

When I fixed my car, I had to recharge the AC. After evacuating for 20 minutes, and checking for leaks, I filled it with R 134. I put in 12 oz and it barely worked. I then put in more while looking for bubbles & monitoring the low side pressure. When the pressure reached the limit on the scale for safe operation, I stopped, but there were still bubbles in the glass. The AC is working well, and is colder then any AC in a car I"ve owned recently.

 

Note that the spec is 15.9 oz +/- 1.1 oz.

 

Our AC is nice & frosty on the hottest of days, and we got teeny bubbles ... so I haven't ever been bothered by it. It wasn't an intuitive call ... just lazy.

 

Toyota's official stance is "charge by weight" in other words add the amount of refrigerant as specified for your model car. Bubbles may appear or not. Most newer Toyotas no longer have sight glasses. Use a set of gauges and a thermometer to determine if the charge is correct. Bear in mind that the pressures will fluctuate as ambient temp changes.

 

I'm sure the 15.9 oz +/- 1 oz is for maximum efficiency. I am also sure there is enough safety margin in the design that you could tolerate more without damaging anything. What I should have done is weighed the cans before & after so I would know what I put in. Didn't think about it. I'm not going to pump it down, and charge it up again, so it stays.
Refrigerant pressure gauges are the industry standard method of checking compressor operation, I don't see why that method is not good enough anyway. Bear68 says the same thing.

 

If you're having to add gas to the ac, it means you have a leak. If the system is working properly, you never have to add gas.

While your system is leaking, you'll be adding gas from time to time. Each time, you're adding a 'few ounces' to an existing charge that is unknown. You just keep adding a little till the suction line is beer can cold. Everytime you open the system to add gas you run the risk of contamination (air or moisture) getting in and that isn't good for any part of the system especially the compressor.

I think it would be better to get the leak fixed, get the system properly evacuated and charged and be done with it. In the long run, it's cheaper than fixing the leak and replacing the compressor. But that's just me.

 

Lately temperatures were reading around 39 - 43 celsius here in karachi. I have noticed that the sightglass has a few bubbles for the initial 5 seconds of starting the car. The bubbles then disqppear. Cooling is fine and chilly. Should i be worried? I have a gen 3 model 2015

Posted via the PriusChat mobile app.

 

NO.
If it ain't broke, don't "fix" it.
Why are you even concerned the least little bit ?

Note: The thread that you posted this question to is TEN YEARS OLD !!

 

That sounds normal. I've attached third gen Repair Manual info. And considering this is second gen forum, their info too.

FWIW, the 2nd gen info (file that doesn't mention 2010) seems more understandable, for both gen's. My take there should be next-to-no bubbles as the compressor's running, then a swirl of bubbles just as it stops. If you run the system for a few minutes, and one of the tubes from the compressor (I forget which) is icy cold, you're good.

More info from a Priuschat member, I took notes:

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From Priuschat member:

@lech auto air conditionin

Posting:

Death toll risers for Prius electric compressors | PriusChat

Subject: DIY check of Prius air conditioning state of charge
(Not definitive, just to give you some idea)

Works on a hot day say 80° plus with your vehicle in the sun set to fresh air mode outside not recycle all your doors open run your AC on high fan speed cold as possible but not max because that will set your air selector to recycle you do not want recycle selected.
Run your air conditioning for about 10 minutes to let it equalize and stabilize on that 80° plus day. Now this is where people get hands burnt and fingers chopped by fans that turn on. If it could be safely done I put my hand all the way down on the suction line as it enters the compressor and it should be nice and cool.
Under ideal conditions and if humidity was high you would see water condensating on all the surface of the metal line set the suction side going all the way back to the compressor. You cannot use condensation of water on the line if the humidity is low because it probably will not condensate because the dewpoint is too high.
If the return gas line is cool the compressor and a electric windings like that cool refrigerant flow keeping the compressor happy with a long life and oil return.

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So i measure the air being blown by the AC with Lo setting and fan at full speed. The minimum temperature i cud get was 8 celsius or 46 F. Is it good enough?

Posted via the PriusChat mobile app.

 

You are lucky it is that low.
Whether or not that is "good enough" for YOU is another question.
Honestly, many systems don't get that cold.