did some Ac work today ..

[Theiceman]

last fall my son complained of Ac not cold. I put the gauges on it and both high and low side were very low. i thought maybe I did something wrong so went to recheck it and heard freon rushing out of a loose hose at the gauge so packed it in.

so today I went back at it. I was surprised to see the econ light not on, so enough pressure to keep compressor on at least.
I decided to let the tiny last bit of freon escape and risk the wrath of Greta

so baseline was econ light on ( no AC) would not turn on, so started the car put my can on the low side and watched the high side. that stuff goes in fast !!. before I knew it half the can was in. the gauge on my can said Ac was full and high side not moved.
still could not turn econ light off.
turned off car waited 10 minutes , went back . started car, econ light off. immediately high side builds.. can now says needs more .
slowly filled more until can said it was full ( about 630 grams).
took it off and put low pressure gauge back on .

low side 35 high side 150..
range 35-45 and for my ambient high side 150-170 .

a little on the low side but in range.

vent temp was about 50f which is fine with me.
I think adding more 134 probably would make it perform better, but spec is 500+/- 25 and I'm at 630 so decided not to mess with it .
maybe all 134a is a bit different, but just glad I could get some cold in the cabin.

oh I also checked my 8.5 next to it for reference as that thing feels ice cold .

that's the last pic with the black background
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[VinnysS4]

Resting(car off) pressures will equalize between the high side and the low side and you want about 1 psi per ambient temperature in F. So if its 70 outside, with the manifold gauges hooked up you should see 70 psi. on both sides. I would fill it until you get to those pressures..whatever that may be that day. If the pressure in the system is higher than the cans pressure, put the can into a bucket of warm/hot water before you do it and the pressure will be higher in the can. You can always fill it on the low side with the car running, but in order to make sure you have the correct amount, the ambient temperature trick works good. You can always fill it and shut it off and watch for the pressures to equalize.

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[Theiceman]

Resting(car off) pressures will equalize between the high side and the low side and you want about 1 psi per ambient temperature in F. So if its 70 outside, with the manifold gauges hooked up you should see 70 psi. on both sides. I would fill it until you get to those pressures..whatever that may be that day. If the pressure in the system is higher than the cans pressure, put the can into a bucket of warm/hot water before you do it and the pressure will be higher in the can. You can always fill it on the low side with the car running, but in order to make sure you have the correct amount, the ambient temperature trick works good. You can always fill it and shut it off and watch for the pressures to equalize.

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that's great advice thanks. current plan is to leave it and see if it drops off . ( see if there is a leak ) . I have a second can to go back at it. what are your thoughts on stated amount of freon ( label on the hood) vs what I put in ? ( 630). dont worry about it ?

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[Kevin C]

My take: System pressure with the pump of is determined only by the temperature of liquid in the system. You could have 10 cc of R134 or you could have a 1000 cc, the pressure is only determine by having volume for the gas to expand into and the fluids temperature. You cant determine charge on a non running system unless you pump it down and refill by weight.

As far as adding more freon that is called out by the manufacturer there is a risk that under certain conditions liquid refrigerant may reach the inlet port of the pump. The more you go above the recommended amount the greater the risk. R12 systems were pretty tolerant of fill amounts, R134 is not. There is no easy way to know how much is too much. The danger is the pressures in the pump will hit about 10x normal, continued slugging can case the pump to fail. You can getaway with an overcharged system for a while until the operating conditions cause the amount of condensed refrigerant to increase. Odds are you wont see those conditions when you have the car sitting in the shop checking the pressures.

[VinnysS4]

that's great advice thanks. current plan is to leave it and see if it drops off . ( see if there is a leak ) . I have a second can to go back at it. what are your thoughts on stated amount of freon ( label on the hood) vs what I put in ? ( 630). dont worry about it ?

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I wouldn't worry about it to be honest. The way its normally done is the system emptied and weighed and a weighed amount put in. Just because the can say 630, doesn't mean it all made it into the system.
If you put an amount in and the pressures aren't quite what they should be, then you probably need more refrigerant. If you put more and the pressures don't change, then you likely have a restriction in the system. Just keep an eye on the temps from the dash. You should get 30 to 50 degrees below ambient temperature, to a certain point. I just filled my Q7s refrigerant. After filling(took 3 cans) I was able to get 50 below ambient temperature. 34 degrees on a 80 degree day

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