Automotive Air Conditioning Information Forum

Can you get suction pipe temperature and pressure at the same time? Need to calculate suction superheat to see if the TXV is adjusted close to correct.

If you are flooding the suction line with liquid you are loosing performance. If this is the case, discharge line will be abnormally cool, get pressure and temperature of discharge line at the same time?

I think you probably need to carefully determine correct charge before you try tweaking any hardware.

The basic idea is to hold constant high load conditions, girlfriend working the pedal, hold 1500 RPM, high blower, hot day, windows down.
Start with a undercharge (suction pipe will be warm, evap will only be cold from some portions, suction pressure will be lower than you have now). Carefully weigh this amount, small cans are fine keep track of how many. Weigh partials on a postal scale. If suction pressure goes below 28 psig, add refrigerant until you get above 28, keep track of the weight.

Add refrigerant in small amounts, record refrigerant weight, high side pressure, low side pressure, vent temp, suction temp, discharge temp. Keep adding in small increments.
At every addition, things will change, suction pressure will go slightly up, discharge slightly up, performance getting better.

It will then start to perform the same with each addition. This is the receiver can filling up, you are at nearly optimum, keep adding small increments.

Once the receiver is full, the next addition will cause high side pressure to increase. Liquid is backing up in the last passes of the condenser creating subcool ( a good thing).

I can't say where your best charge will be, depends on how your condenser is built. I would measure press/temp at condenser out and charge to 20F subcooling, but who knows. Maybe stop when the receiver is full, maybe stop after a few more charge additions.

Thanks for all the info and asking important questions, folks.

What's my next move? Should I recover the r134 and start fresh? Sounds like this is the best move.

Also, when I do this recovery, and start with a blank slate, I also want to start with a blank slate in terms of oil as well. What are my options there?

I'm thinking once I do the recovery, I'll add oil and then add refrigerant using the process described by DetroitAC and John, to slowly determine the best amount of charge for my homemade setup.

After I recover the r134, i was also considering putting in a new TXV. What do you think about that?

GottaBeCold88 wrote: ↑Sun Jul 17, 2022 7:58 am What's my next move? Should I recover the r134 and start fresh? Sounds like this is the best move.

Yes, I would do that since we don't know how much refrigerant is in there now.

GottaBeCold88 wrote: ↑Sun Jul 17, 2022 7:58 am Also, when I do this recovery, and start with a blank slate, I also want to start with a blank slate in terms of oil as well. What are my options there?

Depends on how much oil was in the new compressor, if any. However, Denso compressors usually ship with three or four ounces of PAG-46 already added from the factory. Do the instructions specify how much oil the compressor came with, or did you pour it out and measure it (which should have been done anyway)?

GottaBeCold88 wrote: ↑Sun Jul 17, 2022 7:58 am I'm thinking once I do the recovery, I'll add oil and then add refrigerant using the process described by DetroitAC and John, to slowly determine the best amount of charge for my homemade setup.

You can add all the oil into the compressor if it will fit. To be on the safe side, I would add an extra 1 ounce or so into the system due to the long hose lengths. If the compressor won't take all the oil (which now should be about 8.25-8.5 ounces), add 1-1/2 ounces each to the condenser, evaporator, and R/D, and add the rest into the compressor. Rotate the compressor main-shaft by hand about a dozen times using a socket wrench if necessary. Don't forget to evacuate the system well just before re-charging it.

GottaBeCold88 wrote: ↑Sun Jul 17, 2022 8:40 am After I recover the r134, i was also considering putting in a new TXV. What do you think about that?

The TXV is new, and it came with the new evaporator. So I'm guessing that it should be okay. But if you suspect that it's malfunctioning or that it sustained external damage to its fragile sensing tube, go ahead and replace it with another one from the same manufacturer so that you'll get the correct part for your evaporator.

GottaBeCold88 wrote: ↑Sun Jul 17, 2022 8:40 am After I recover the r134, i was also considering putting in a new TXV. What do you think about that?

I've seen no evidence that your TXV is a problem, sensing bulb installation looks kinda wonky, but there is only one picture. Bulb on the suction line should be completely insulated.

Note: JohnHere edited the following post for clarity:

Depends on how much oil was in the new compressor, if any. However, Denso compressors usually ship with three or four ounces of PAG-46 already added from the factory. Do the instructions specify how much oil the compressor came with, or did you pour it out and measure it (which should have been done anyway)?

The compressor came shipped with oil in it. But I'm not sure how much oil I lost when I recovered refrigerant when I overcharged and the system started to shake and I got freaked out.

So that's why I'm a little concerned about how much oil I may or may not have. I did add a couple ounces back in via 2 oil+charge cans. So, not sure if you think I'm okay to just recover and recharge, or if I should do a more in-depth oil job as well.

If you guys think I'm okay doing a recovery, then putting the amount of oil removed back in before I evacuated and recharge, I can try do to that today. But if you think I need to fully drain the oil and start over, I can do that too. Let me know what you think is best!

Also, I won't replace the TVX for now. Thanks for the advice!

GottaBeCold88 wrote: ↑Mon Jul 18, 2022 7:27 am The compressor came shipped with oil in it. But I'm not sure how much oil I lost when I recovered refrigerant when I overcharged and the system started to shake and I got freaked out.
So that's why I'm a little concerned about how much oil I may or may not have. I did add a couple ounces back in via 2 oil+charge cans. So, not sure if you think I'm okay to just recover and recharge, or if I should do a more in-depth oil job as well.
If you guys think I'm okay doing a recovery, then putting the amount of oil removed back in before I evacuated and recharge, I can try do to that today. But if you think I need to fully drain the oil and start over, I can do that too. Let me know what you think is best!

Based on my (unofficial) calculations, I would want 8 ounces of oil in this system, perhaps a little more, as previously stated.

However, now that you have run the system and the oil has been distributed to the various components, it's sheer guesswork as to how much is in there now or how much was in it to start. Unfortunately, there's nothing to "gauge" the amount of oil, like a dipstick.

It's always best to start with a dry system, add the oil according to specifications—or, in this instance, according to calculations—then evacuate and charge it. Short of removing every component, flushing the oil out of each one, and starting from scratch—which would be a lot of extra work—we'll make some educated presumptions instead.

Since the system was already run, we can presuppose that "some" oil now remains inside not only the condenser, evaporator, R/D, and hoses (to a lesser extent), but also inside the compressor. Exactly how much is guesswork. But typically, in a properly charged factory system that has been run, 1 ounce to 1-1/2 ounces will remain in the condenser and evaporator, while about 1/2 ounce to 1 ounce will remain in the R/D. An inconsequential amount will remain in the lines and hoses. If that presupposition holds true, then conservatively, you should add 4 ounces (plus about 1/2 ounce more, if it will take it) to the fully drained compressor to make up the difference.

Great! Thanks so much.

Please forgive my ignorance. To fully drain my compressor, I would have to turn it upside down and rotate it after I did the recovery? Or does the recovery take all the oil out of the compressor?

Depends on the type of recovery machine. Some remove the oil some don't. Using a shop electric vacuum pump won't remove any.
I would remove the comp and empty as you described regardless to be sure, you are trying to get it all out so you can start fresh