1998 XJ Sport 4.0 Automatic

I'm not an expert on ac systems, but I do have some knowledge.

We installed all new ac components (compressor, liquid/orifice line, suction/discharge lines, valves, seals, evaporator, accumulator, condenser) and insured the proper 8.1 oz of pag100 installed.

Using a set of good gages and pump, we evacuated the system perfectly and left it over night to be sure of no leaks. It held perfectly.

While charging the system this morning we lost track of the weight of r134a pulled into the system.
I decided to stop the charging process when we couldn't recall the full weight of the fresh second 12 oz. can and didn't have it written down after sucking on it for a few min.
I also believe we forgot to purge the charging line after hooking up the second can and sucked whatever air was in the charging line into the system.
As the system stands now; I believe we're not fully charged, underweight with a little air contamination in the system....

I figure it's not a big deal to just properly re-evacuate and re-charge the system again, chalk it up as a learning experience.

But then though I should ask anyone more familiar than I if there is anything I'm missing...?
Is it no big deal to just properly re-evacuate and start over or should I be aware of anything else?
Do I need to add any oil to compensate for what might get lost in re-evacuating? I'm not sure but I wouldn't think so...?
Anything else?

I do not think there would be, but is there any way to know how much refrigerant is in the system based on the gages?
"Figure 6 Performance Temperature and Pressure" in the FSM is the only reference table I know of.

As an aside, how realistically precise do we need to be on 20.00 oz of refrigerant into the system?
(I do not see my kid setting a can with a hose dangling from it on a kitchen scale which reads in 100ths of an oz to be all that realistic.) :-)

Thank you for your time...

 

As long as you purged all the lines before the 1st can and didn't disconnect the charging hose from the manifold gauge, I think you're fine.

While the chart is for diagnostic and testing purposes only, You can use them to "back in" to the charge level. It won't tell you the Oz you put in, only how the system is operating. If it's in spec, you're close enough. You may want to leave the gauges attached, wait until have a big air temp change and engine has cooled off and check again. Checking at few different temps can get a better read that's it operating correctly.

The only way to be sure how much is to recover and evacuate the system and start over. While not Ozone depleting, R-134a is a green house gas. So, other than the cost in time and money it's no big deal.

FWIW, I use a kitchen scale to weigh mine. I setup some kind of platform (usually my BD Workmate) and put the scale, canister connected to the hose, canister sitting in a small pot of warm water, pot on the scale. With everything in place, I zero the scale.

 

I just replaced the orifice tube, suction-discharge line, and accumulator on my 1999. I checked pressures and ended up putting in 2 full 12 oz cans in my system. My ac blows 50 degrees on an 85 degree high humidity Arkansas day which is not bad.

 

I would want to hook up some gauges to be sure, but I think you are way overcharged

 

The amount of air (non condensables) in your lines is not very much. Charging by weight is a great way to do it if you have accurate scales to do so. Otherwise you need to do it by pressure and if you have the equipment by superheat. That is the difference between gas temp and line temp at the compressor. But if you don't have that capability, then by gas temp (or pressure) on the return line. Is there a gauge on the can you used to charge?

 

When I replaced and charged my system it was about 95 degress 60+ percent humidity. My pressures were about 38psi and 250psi. They were on the low side of the charts I found online.

 

Spec is 20 ounces. So yeah 24 ounces is a bit overcharged.

 

Thanks Saudade....
I went and did the evacuate and charge again with the kid this afternoon...
I now understand the problems he was talking about related to loosing track of the weight...
What a PITA it is to have a kitchen scale that auto-shuts off every three minutes.

I like your idea on the warm water bath for the can and used it... Good call... ;-)

4.3L XJ
I am doing this with some ok gages, not those one step charge cans and definitely not loaners from the parts store.
I'm curious what the system pressure typically equalizes to when off and returned to steady state.
My block cooled for about an hour or two when I removed the gages, but the system seemed equalized: low and high gages reading just under 100....
Does an equalized steady state system pressure of about 90-100 seem about right?


It was about 85-90*F with bright hot sun today in the far west burbs of HUMID Chicago, and since doing this in direct sun figure hotter.
I was a little concerned to to see that when fully charged with exactly 20.00 oz. of straight r134a according to the kitchen scale (LOL)), I was measuring ~350 on the high side and ~43 on the low...
The high side seems a little high according to "Figure 6 Performance Temperature and Pressure" from the FSM...
Anyone know if this is typical,,, or something else...? Sound about right or no??

Thanks again for your time...

 

Steady state will have pressures on both sides equal. That is not the pressure you should be worried about. It is the pressure when operating that is what you look at. Operating sounds about right. It is the temps that correspond to the pressures I go by. The pressures can vary with types of refrigerant used

 

Generally, I try to check AC pressures in the shade. Direct sunlight heats up the vehicle, the ground, the tools, everything so actual ambient temp in the shade may be lower. Also, did you use a local thermometer or one from a weather source? Even an outside air temp sensor can read differently depending on the angle you park relative to the sun.

If you're certain you got 20oz in, it's filled. Checking pressures ensure the rest of the system is operating properly.

So rather than use ambient (85-90 in your case) I'd bump it up one. So using assuming 100 deg, you're pretty close. I'd leave it there and try if for a few days. Maybe even go back and check pressures later on when the air temp is lower.

As 4.3 said, once off, pressures will equalize after a short while. The pressure will also lower as the engine cools off.