AC won't take freon

[White Stripe]

Jen, with the engine off (compressor not turning) you are looking at the 'static' pressure on your gauges. The system will equalize and the readings on both gauges will be roughly the same. The static pressure for 134a at the ambient you cited (88° F.) would be about what your gauges are showing (96 psi). Don't worry yourself with that.

The static pressure is a mostly useless figure EXCEPT to show you have some amount of liquid refrigerant in the system. It does NOT indicate how much is in the system. Static pressure will be the same if you had one drop of liquid refrigerant in the system or two pounds. So don't be concerned with that.

Let's move on. It will be pointless to continue until you find the reason the compressor clutch is not engaging. You have already introduced one can (some amount of weight? into the system) and you have almost 100 psi static pressure, so we know that is enough to activate the pressure switch (if it is not faulty).

Let's turn our attention to tracing the electrical circuit and see IF you have power (12 volts) getting to the compressor clutch.

You'll want to check the easy stuff first (fuses), then dash switches, wiring. But we have to settle that issue before moving forward. Once we have the electrical system calling for the compressor clutch to engage...we can go back to the charging phase. You have plenty of static pressure...so DON'T add more refrigerant at this juncture.

Let us know what you find.

Flint.

How would static pressure be the same regardless of the amount of refrigerant? The more refrigerant I put into a ac system the more static pressure their is. As far as I know, when r134 is static in a automotive ac system it is always a gas, not a liquid. If it was partially a liquid, you would risk hydro locking the compressor. The state of r134 according to a chemical calculator at 90 or 100psi at 88 degrees is its a gas. A properly charged r134 automotive system static pressure will not be 95psi. According to her static pressures, the system is overcharged quite a bit. But I agree with you that right now the concern should be to figure out why the compressor isn't activating. It certainly isn't due to too little refrigerant.
Fluid Property Calculator

 

[Aloha Jen]

I really don't recommend charging it with cans. It's very easy to overcharge and difficult to get the correct charge amount. Just a little overcharging will lower the systems efficiency and you won't get maximum cooling potential. Looking at your gauges with the system off it would seem you have overcharged it. That being the case the system should operate. Turn key on engine off push ac button on. Check for power at your fuse and Chek the fuse. If that's good, Check for power going into and out of the pressure switch with a test light or volt meter. If you don't have power to your pressure switch, the ac switch on the dash may be bad. If you have power into the pressure switch but not out of, you may have a bad pressure switch. I would especially suspect any parts that are old or used and one of them will likely be the culprit.

I don't understand how I could have overcharged the system? It calls for 30oz of r134 (two and a half 12oz cans right), and have only put in maybe less the one and a half 12oz cans so far. The system was completely empty, and vacuumed down before charging. I am only just learning about all this, so please pardon my ignorance on the workings of AC systems, but how is it possible to overcharge it with only one and a half 12oz cans in there so far?

We will start checking for power at all the locations you suggested to try and locate an electrical issue. There is a brand new denso pressure switch in there (as well as a new denso evaporator core and denso expansion valve), so I sure hope it is good! But will check those power sources and report back.

 

[Aloha Jen]

Jen, with the engine off (compressor not turning) you are looking at the 'static' pressure on your gauges. The system will equalize and the readings on both gauges will be roughly the same. The static pressure for 134a at the ambient you cited (88° F.) would be about what your gauges are showing (96 psi). Don't worry yourself with that.

The static pressure is a mostly useless figure EXCEPT to show you have some amount of liquid refrigerant in the system. It does NOT indicate how much is in the system. Static pressure will be the same if you had one drop of liquid refrigerant in the system or two pounds. So don't be concerned with that.

Let's move on. It will be pointless to continue until you find the reason the compressor clutch is not engaging. You have already introduced one can (some amount of weight? into the system) and you have almost 100 psi static pressure, so we know that is enough to activate the pressure switch (if it is not faulty).

Let's turn our attention to tracing the electrical circuit and see IF you have power (12 volts) getting to the compressor clutch.

You'll want to check the easy stuff first (fuses), then dash switches, wiring. But we have to settle that issue before moving forward. Once we have the electrical system calling for the compressor clutch to engage...we can go back to the charging phase. You have plenty of static pressure...so DON'T add more refrigerant at this juncture.

Let us know what you find.

Flint.

Thanks for the explanation, it's a relief to know those static psi readings are ok for the ambient temperature. We will not charge it any further for now.
We will check all of those electrical connections you mentioned to see if power is getting to where it needs to be and will report back.

 

[flintknapper]

I don't understand how I could have overcharged the system? It calls for 30oz of r134 (two and a half 12oz cans right), and have only put in maybe less the one and a half 12oz cans so far. The system was completely empty, and vacuumed down before charging. I am only just learning about all this, so please pardon my ignorance on the workings of AC systems, but how is it possible to overcharge it with only one and a half 12oz cans in there so far?

We will start checking for power at all the locations you suggested to try and locate an electrical issue. There is a brand new denso pressure switch in there (as well as a new denso evaporator core and denso expansion valve), so I sure hope it is good! But will check those power sources and report back.

You haven't overcharged your system. You are likely to get some advice here from folks who have a 'misunderstanding' about certain aspects of Automotive A/C.

Find out about your issue with getting power to the compressor clutch and we can go from there.

I will check back as I have time. I'm sure there are others who are familiar with proper A/C charging practices that can answer your questions as well. All 'correct' information is welcome.

 

[flintknapper]

Thanks for the explanation, it's a relief to know those static psi readings are ok for the ambient temperature. We will not charge it any further for now.
We will check all of those electrical connections you mentioned to see if power is getting to where it needs to be and will report back.

Yes, but understand...I am simply saying we are NOT going to use 'static' pressure as a diagnostic tool to determine the correct refrigerant charge. Static pressure is useful to indicate certain conditions but the amount of liquid refrigerant isn't one of them.

Just don't be panicked by the static pressure reading you are seeing, it doesn't mean anything significant at this point.

 

[flintknapper]

How would static pressure be the same regardless of the amount of refrigerant? The more refrigerant I put into a ac system the more static pressure their is. As far as I know, when r134 is static in a automotive ac system it is always a gas, not a liquid. If it was partially a liquid, you would risk hydro locking the compressor. The state of r134 according to a chemical calculator at 90 or 100psi at 88 degrees is its a gas. A properly charged r134 automotive system static pressure will not be 95psi. According to her static pressures, the system is overcharged quite a bit. But I agree with you that right now the concern should be to figure out why the compressor isn't activating. It certainly isn't due to too little refrigerant.
Fluid Property Calculator

I don't have the time or inclination to argue with you about static pressure. It is a measure of vapor pressure and that vapor pressure is dependent upon temperature NOT how much liquid refrigerant is in the system. We are trying to establish whether or not the system has ANY liquid refrigerant in it (dual phase condition). The system will accept an amount of refrigerant (small amount) that simply remains a vapor. What we want is for the charge to reach the saturation point where you have both liquid and vapor (dual phase). You can NOT tell how much liquid is present by virtue of a static gauge reading, only that SOME liquid is present owing to a minimum pressure reading at a specific temperature.

I don't want this thread to turn into a tutorial or a venue for everyone's arguments. We just want to get the lady's A/C going with least amount of strife.

Troubleshooting with Gauges FAQ

There are tons of forums and sites you can visit with your questions.

 

[Twinair]

How would static pressure be the same regardless of the amount of refrigerant? The more refrigerant I put into a ac system the more static pressure their is. As far as I know, when r134 is static in a automotive ac system it is always a gas, not a liquid. If it was partially a liquid, you would risk hydro locking the compressor. The state of r134 according to a chemical calculator at 90 or 100psi at 88 degrees is its a gas. A properly charged r134 automotive system static pressure will not be 95psi. According to her static pressures, the system is overcharged quite a bit. But I agree with you that right now the concern should be to figure out why the compressor isn't activating. It certainly isn't due to too little refrigerant.
Fluid Property Calculator

Static pressure is directly related to temperature and NOT the amount of refrigerant that is in the system. One could have an undercharged system that would read the same static pressure as an over charged system given the two systems are at the same temperature. Google search R-134A TP chart. There is absolutely no way of knowing that a system is overcharged unless you recover the refrigerant and weigh what comes out. @alohajen check high and low pressure switches and compressor fuse. When charging from an evacuated system, charge liquid through the high side. One should be able to completely charge a system with this method unless you're using 12oz cans. The problem with 12oz cans is that by the time you switch to the next can the high and low side pressures equalize and can no longer take the refrigerant from the new can. At that point you need to use the compressor to create a pressure difference and continue charging system this time through the low side as a liquid. Meter the refrigerant entering the system so as not to liquid slug the compressor.

 

[White Stripe]

I don't understand how I could have overcharged the system? It calls for 30oz of r134 (two and a half 12oz cans right), and have only put in maybe less the one and a half 12oz cans so far. The system was completely empty, and vacuumed down before charging. I am only just learning about all this, so please pardon my ignorance on the workings of AC systems, but how is it possible to overcharge it with only one and a half 12oz cans in there so far?

We will start checking for power at all the locations you suggested to try and locate an electrical issue. There is a brand new denso pressure switch in there (as well as a new denso evaporator core and denso expansion valve), so I sure hope it is good! But will check those power sources and report back.

I'm not sure. I've never added the small cans to a system. I have access to a.c. machines so I've always used those. I'm not trying to mislead you or anything, just my opinion ion from what I know.

 

[flintknapper]

Static pressure is directly related to temperature and NOT the amount of refrigerant that is in the system. One could have an undercharged system that would read the same static pressure as an over charged system given the two systems are at the same temperature. Google search R-134A TP chart. There is absolutely no way of knowing that a system is overcharged unless you recover the refrigerant and weigh what comes out. @alohajen check high and low pressure switches and compressor fuse. When charging from an evacuated system, charge liquid through the high side. One should be able to completely charge a system with this method unless you're using 12oz cans.

Thank You!

 

[White Stripe]

Static pressure is directly related to temperature and NOT the amount of refrigerant that is in the system. One could have an undercharged system that would read the same static pressure as an over charged system given the two systems are at the same temperature. Google search R-134A TP chart. There is absolutely no way of knowing that a system is overcharged unless you recover the refrigerant and weigh what comes out. @alohajen check high and low pressure switches and compressor fuse. When charging from an evacuated system, charge liquid through the high side. One should be able to completely charge a system with this method unless you're using 12oz cans.

Ok but the more refrigerant I put in a automotive system the higher the static pressure goes on the a.c. gauges. That's what I've noticed. Why is that the case?

 

[BILT4ME]

@Aloha Jen :

I just helped a friend charge his 94 LC from empty. We vacuumed down the system to -28" HG. Let it sit for 5 minutes, per the FSM.

I could not find in the FSM about the total Oz. required from empty, but the 30 Oz is close.

We added almost 4 cans. The clutch didn't engage until near the end of the second can. I was beginning to think something was wrong and was about to test the clutch when it engaged.

Hopefully, you refilled any lost oil with replaced components. That should be done first.

The sight glass on the LF fender was VERY helpful in conjunction with the FSM. If there is nothing, there is not enough. If there are bubbles, there's not enough. If it gets cloudy, then clears, it is working properly.

I set it not by how many OZ we put in, but by the final operating pressures. The FSM gives the readings for minimum and maximum in MPa for both the low side and high side.

I THINK the low side was 22.7 PSI to 36.7 PSI and the high side was 198 PSI to 227 PSI. This is WHILE the compressor is running with the clutch engaged.

All this took over 2 hours to get the 4 cans into the system. I would set the can on the side of the block so the cooling fan would blow the engine heat over the cans during filling. Only fill on the low side with vapor if possible.

On a 70°F day, he was blowing 38°F air into his truck.

Hold the engine at 1500-2000 RPM, all doors and windows fully open, AC on, Recirculation ON, Fan on HIGH.

Good Luck!

 

[cruiserfj45]

Ok but the more refrigerant I put in a automotive system the higher the static pressure goes on the a.c. gauges. That's what I've noticed. Why is that the case?

Yes as you fill the system the pressure will go up, but if you let it sit and level out the pressure will stabilize and match the pressure to temperature. some will be liquid and some will be gas. Once you start moving it pressure/temperature will be different, but in a static state it will match the chart.

@Aloha Jen You are on the right track chasing the electrical circuit down. When the compressor is not on you can charge the low side with gas (can right side up) and the high side with liquid (can up side down, and much faster). Once it has maxed out and refrigerant no longer transfers between can and vehicle you must charge through the low side with the can right side up (gas). If you try to charge the low side with liquid while the compressor is running you do run the risk of hydro locking the compressor, but it is highly un likely to do that as the refrigerant is going through the gauges. I don't have a machine so when I recharge a system I have a thermometer in the center duct, one in the cowl intake just below the pass side wiper arm to measure intake air temp, one outside in the shade, and fan on 3/4 speed with fresh air. A good system will blow temperatures 25 to 35 degrees below intake air temp.

The way the system works is by taking heat energy out of the air and it can only pull so much out. The bigger the cabin the longer it takes. This is why I only charge biased on how much the air temperature drops biased on intake temp. Think of it as a row of dump trucks taking dirt out of a mine. Each time one comes out it has a certain amount of dirt (British thermal units BTU). When you are using R134 your dump trucks just got a little smaller and there are less of them. After some time you will get the same amount of dirt out (min temp) but it takes longer. Because you are using R134 on a R12 system you CAN NOT use the sight glass an an accurate way to charge the system. If you were using R12 the sight glass is the best way to charge the system.

Feel free to PM me and I will give you my number and I can walk you guys through this over the phone and see if we cant get that system sorted out, but your primary concern is getting power to the clutch without having to jumper it.

 

[Twinair]

Ok but the more refrigerant I put in a automotive system the higher the static pressure goes on the a.c. gauges. That's what I've noticed. Why is that the case?

If you are adding refrigerant to a system then your pressures are no longer static. Static means the system is at rest and there are no other forces at play other than temperature. Temperature dictates refrigerant pressure in a static system. If you add refrigerant to a system then of course the pressure of the system will increase. Once you stop adding refrigerant, the pressure will equalize and then the pressure will adjust to the system's ambient temperature. I can tell you with certainty what refrigerant is in a system if all I had was the pressure and the temperature of the refrigerant in a static system. Anyone can if he has access to PT charts of common refrigerants.

 

[Twinair]

A PT chart is an invaluable refrigeration tool.

 

[White Stripe]

Huh interesting something I'll have to look into. Thanks.

 

[Aloha Jen]

FROSTY UPDATE: I have cold AC now! I really appreciate all the advice and instructions you guys gave, we definitely would not have been able to do it without your help. However, the fix was so easy that I am a little embarrassed to tell it. Also, it was primarily my fault.....as I had ONE easy job during the install, to use my tiny lady hands to reach inside the dash to plug in all the AC connections. I had plugged the wrong connector into the AC "ON" button plug....giving it no power, thus not passing that power on to the pressure switch and compressor! In my defense, Toyota put and identical 3 pin plug right next to it that plugged right in perfectly, so it was the logical choice. But when Mike pulled it off and tested it like you guys suggested, no power showed on the multimeter, and that's when he noticed the other identical plug dangling a foot away that just happened to have power to it when the fan was turned on . Plugged it in, and boom.....AC clutch engaged and blew ice cold air from the vents! No more sweating it out in the mid day Hawaiian heat and having to drive in a bikini everywhere just to stay cool! Thanks again!!!!!!!

 

[flintknapper]

FROSTY UPDATE: I have cold AC now! I really appreciate all the advice and instructions you guys gave, we definitely would not have been able to do it without your help. However, the fix was so easy that I am a little embarrassed to tell it. Also, it was primarily my fault.....as I had ONE easy job during the install, to use my tiny lady hands to reach inside the dash to plug in all the AC connections. I had plugged the wrong connector into the AC "ON" button plug....giving it no power, thus not passing that power on to the pressure switch and compressor! In my defense, Toyota put and identical 3 pin plug right next to it that plugged right in perfectly, so it was the logical choice. But when Mike pulled it off and tested it like you guys suggested, no power showed on the multimeter, and that's when he noticed the other identical plug dangling a foot away that just happened to have power to it when the fan was turned on . Plugged it in, and boom.....AC clutch engaged and blew ice cold air from the vents! No more sweating it out in the mid day Hawaiian heat and having to drive in a bikini everywhere just to stay cool! Thanks again!!!!!!!

Atta Girl!

Proud of you (and Mike), you guys methodically tracked down the problem and persevered. Good Job.


Flint.

 

[White Stripe]

I don't have the time or inclination to argue with you about static pressure. It is a measure of vapor pressure and that vapor pressure is dependent upon temperature NOT how much liquid refrigerant is in the system. We are trying to establish whether or not the system has ANY liquid refrigerant in it (dual phase condition). The system will accept an amount of refrigerant (small amount) that simply remains a vapor. What we want is for the charge to reach the saturation point where you have both liquid and vapor (dual phase). You can NOT tell how much liquid is present by virtue of a static gauge reading, only that SOME liquid is present owing to a minimum pressure reading at a specific temperature.

I don't want this thread to turn into a tutorial or a venue for everyone's arguments. We just want to get the lady's A/C going with least amount of strife.

Troubleshooting with Gauges FAQ

There are tons of forums and sites you can visit with your questions.

You are right about static pressure. I looked some info on the web and did my first a.c. job of the year today and verified it. Thanks for correcting me. I don't want to act like a know it all. Maybe I learned that about static pressure b4 or maybe it's totally new to me. I've been doing so few a.c. jobs the last few years I can't say. I moved to a cooler area of the country a few years ago. B4 that I was doing a.c. work quite often.

 

[White Stripe]

FROSTY UPDATE: I have cold AC now! I really appreciate all the advice and instructions you guys gave, we definitely would not have been able to do it without your help. However, the fix was so easy that I am a little embarrassed to tell it. Also, it was primarily my fault.....as I had ONE easy job during the install, to use my tiny lady hands to reach inside the dash to plug in all the AC connections. I had plugged the wrong connector into the AC "ON" button plug....giving it no power, thus not passing that power on to the pressure switch and compressor! In my defense, Toyota put and identical 3 pin plug right next to it that plugged right in perfectly, so it was the logical choice. But when Mike pulled it off and tested it like you guys suggested, no power showed on the multimeter, and that's when he noticed the other identical plug dangling a foot away that just happened to have power to it when the fan was turned on . Plugged it in, and boom.....AC clutch engaged and blew ice cold air from the vents! No more sweating it out in the mid day Hawaiian heat and having to drive in a bikini everywhere just to stay cool! Thanks again!!!!!!!

Glad it's working!

 

[shocktower]

Ok I did a search Foo, to get my new system chillin, so I pulled a consistent vacuum , using gauges and I trying to charge the system but my friend said the compressor must engage, and I think the system needs freon in it to get the clutch to engage, he told me, to jumper the Pressure switch by the battery and I get nothing. @flintknapper I see you are very knowledgeable on the AC system because I am not . I am using a new compressor and this is on my Cummins swapped 80