Hi y'all. I am starting to feel a little crazy on my AC project and could use a second set of eyes and input from the forums. I keep thinking of the phrase, insanity is repeating the same thing expecting different results. I have been on the fence about updating the AC as I too have the ambition to one day do an engine swap. I had been debating how much can be done that will be compatible and not have to rework or repurchase parts. Despite that, and with enough reading I was feeling the urge to keep driving in the Houston heat.

Loading refrigerant, high side closed

Last week, I ordered the compressor, an updated condenser, accumulator, red orifice tube, and new hoses. R134a is readily available so I chose to follow that path. I installed the new system Saturday. Yes, it was possible to pull the condenser without removing the radiator, it leaned over just fine. I pulled vacuum for over an hour because its about 100% humidity and called it a day.

Sunday I saw there were no leaks, the pressures were still the same; it was time to start recharging. The pump came preloaded with 3 oz of PAG150 (I have seen recommendations for the lighter weight here). I started loading with the 3oz can of oil to draw in under vacuum. I was able to load about half to 2/3 of that can. I switched to loading the refrigerant and it did not act as I had anticipated. The car was running and the compressor was not clicking on at all and it seemed to spike the low pressure port to about 105-110 psi. I jumped the low pressor actuator switch to engage the compressor and try to get the system to start drawing in the refrigerant. At this point I thought that it may need a new low pressure switch so I ran out and got a new one. Swapped, and then restarted the vacuum process. Once settled again I restarted loading and similar high pressures with some refrigerant going in. I called it a day here.

Last night I started the car and the compressor started kicking on and off and it drew in almost a full can. At this point I tried to load the remaining oil without success. I tried increasing idle and jumping the compressor to keep it running a little longer but I seem to have hit the same wall. At one point I was frustrated and turned the can upside down to see if I can get something going. The sight glass got some liquid in it but did not pull it into the car for a while. I stepped away to let the system cool a little and went back to the compressor hooked to the sensor and was able to run it in eventually. Finally after over an hour of trying to load the compressor did not sound happy, everything was hot, and I called it a night. I am thinking of injecting oil to the yellow line then applying more refrigerant tonight. My shop temp last night was still about 90 degrees. High pressure side came up to about 100-150psi, I don’t have a note in front of me on where it settled at the end of the day. It seems odd it was lagging but starting to build.

Thirdgen.org has been a great resource with lots of information, some of these posts are old enough to legally drink. After scouring the forums, internet, youtube and even AI, I am stuck. Am I missing something, should I open up the system and start over, or can these take a while to load in a hot environment? I expected the refrigerant to move to the system quicker and the can to get a little cold and this has not been the case. Anything else to check or do yall to know anything else?

 

Refrigerant will not go into the system if the compressor is not running. It's not like pouring water from a hose into a jug. Reason being, the pressure inside the system rises almost instantly to the same pressure as what's in the can as soon as there's any significant amount of it in there, namely, the equilibrium vapor pressure of the refrigerant, at whatever temperature it's at; and since the pressures in the can and the system are then equal, no further flow occurs. That pressure will be anywhere from 90 psi or so at room temp, up to near 140 psi at 100°F. https://www.engineeringtoolbox.com/r...es-d_1682.html Once you introduce ANY refrigerant into the system, those will be the pressures you'll see; and as described, no further movement of the cold juice can occur.

Sounds to me like it's all doing EXACTLY what it should do. Which is a good thing.

To charge it, you need to make the compressor run. It has enough oil in it to survive for quite awhile without damage as you add more cold juice and/or oil.

Make yourself a jumper consisting of 2 ¼" male slide terminals and a piece of wire a few inches long, and plug that into the 2 terminals of the low-pressure cutoff switch connector, in place of plugging the connector onto the switch.

Keep in mind also, that an AC system doesn't "generate cold" somehow. It MOVES HEAT, by way of liquid refrigerant evaporating in the evaporator (imagine that!) and becoming cold by doing so (just like your hand feels cold if you pour gasoline on it and then let it evaporate) and absorbing heat out of the cabin air passing over it; once it evaporates, it's a gas, and is somewhat warm, or at least warmer than it was when it first evaporated; it is drawn into the compressor and compressed, and becomes a hot (VERY hot) gas under high pressure; it is sent to the condenser, where it (wait for it!!) condenses into a liquid, releasing the heat that it had picked up from the cabin, and allowing the radiator fan to pass ambient air over it; this moderately warm liquid then flows through the orifice tube, which releases a steady small stream of liquid into the evaporator, where it goes through the whole cycle again. Note that it PICKS UP heat from the cabin via the air moved by the blower motor, and RELEASES IT into the world at large via the air moved by the radiator fan. If the rad fan isn't moving enough air, then the juice won't be able to get cooled enough to condense, meaning it then also won't be able to evaporate, meaning it won't be able to absorb heat from the cabin, aka "it doesn't work". Furthermore the pressures in the system can go VERY high under those circumstances which is why there's some form of high-pressure cutoff as well as the low-pressure one which will prevent the compressor from coming on.

On a really hot day, expect the temp at the condenser input to be in the 350 psi kind of range; around 180°F or so. The evap pressure should be somewhere in the 35 - 40 psi neighborhood, which is the vapor pressure of the juice around the freezing point of water (32°F). This will ONLY be the case if LOTS of air is moving through the rad, so BE SURE that your main cooling fan is working as well as it can. In fact, put that nice big blue fan in your pic to where it can help force air through the rad & cond while you're doing this instead of being USELESS off to the side, and it will make your life AHELLUVALOT eeeeezyer.

Incidentally you can (or could at one time) pick up new hood struts at AutoZone or Rockauto or the like. I strongly recomment getting some, speaking of making life eeeeeeezyer.

 

I hope also that you replaced the orifice tube. If not, do that before wasting any more refrigerant on it, and re-evac it afterwards. The stock one is not appropriate for a GM R-12 system filled with R-134A. A better one is the Frod orange/red one; you can get it by asking for the one for about a 96 Crown Vic.

And, make sure your lower air dam, which is a piece of plastic bolted to the underside of the car right below the rad, is intact and in place. The car won't cool at highway speeds without that and the AC certainly won't work right either.

 

Stupid question, but did you remove the valve core from the r12 fittings before you put the adapter fittings on? If not, you're probably not opening the system

 

I fixed that wall of text, formatting looked bad earlier on my phone. Great observations and early commentary, thanks yall.

Air dam is in place, and I did use the red Ford tube. I did reposition that fan when the car was running, that was shooting on my back while bolting everything up.

You know, I don't recall specifically removing a valve from the dryer. You got me thinking. I might go home and carefully poke around there. I may have assumed it was out but the R12 basic configuration left it off for some reason...

Yeah those struts are on the list now, didn't notice them going till I had the light and gauges hanging. Funny enough didn't think anything of it. My first car was an 85 with bad struts on the hatch I kept a yard stick with me for.

 

You wouldn't be the first of the 15th person to not pull those. The worst part is, in the right set of circumstances, the 134 valve core will slightly push on it and allow just the slightest amount of pressure by.

 

You probably know by now, but should have put the oil in the accumulator.
Let us know how it all worked out.

 

Ding, ding, ding! I coped what I pulled out and didn't think anything of it. The system must of had a crappy repair by the previous owner. Looking at it now, I must of thought it would push the inner one down. Either way it was full of junk on the orifice tube before. The compressor must of failed at one point and they tried to put a bandaid on it.

I'm sitting back and watching baseball now while I draw another vacuum. I will raise one for y'all for the help today!

 

Awesome! I love a simple solution.
Update when you're done please

 

I read your list of replacement parts in your first post. It looks like you're reusing your evaporator. Did you flush it? It could have "compressor failure debris" in it. Not only that, but if the system was R12, that mineral oil does not play well with PAG oil.

Good luck getting your AC up and running. AC is a must here in the Houston area!!

 

Food for thought, charging into a vacuum I have never not been able to get the entire first can into a system. Make sure to purge the air out of the charging hose prior to opening the valve. Charge as a liquid into a vacuum through both ports with the can elevated above the system. The first can will go in very quickly. From there you can close the high side valve, start the engine and the cycling switch will already have enough pressure that the compressor will run. Make sure the charging hose is purged everytime you connect a new can if charging from small cans.

 

I do this as well. It's good advice.

 

And I also. Never a good idea to introduce ambient air and moisture back into the system.

 

Yep I did flush the evap, ran clean pretty quick. Used a hose on top and some fuel line at the end of the hard line before the condenser. Once I had the right sizes that was actually pretty easy.

Oh man oh man, I think I got it. I think these rental gauges and pump have seen their share of work this summer. The system held vacuum from last night to this evening just fine. Figured it's darn humid. Vacuumed a little more when I got home tonight because it was just under where I wanted to see the 30" reading but no more change. It pulled the refrigerant in so much easier this time with some of the tips above. I had expected the can to get cold before and they stayed at room temp. This time they were, got sweaty hoses during the charge. Loaded to approximately the 85% of the r134 target. The return line and evap were sweating like they had something to hide.

I took her out for a short spin and was reminded of other things on the list, my noisy Speedo and window that needs adjustment.

 

Oh, wow! Very nice vent temperature!! Congratulations. Now you can drive that car without sweating to death in this Houston heat.

 

That's an incredible vent temperature, definitely at risk of evaporator freezing. If you notice diminished airflow, you may want to adjust the cycling switch ever so slightly so it cycles at a little higher pressure.