What are correct A/C pressures for a charged system?

01eddie · 07-03-2008, 01:24 PM

O.K., Here is where I am at the moment....

A/C didn't work, checked to see that compressor would still click on- it did. Bought a can of "EZ Chill" 134a for $18 at Wally world. came in a tall can with lubricant added and leak sealer. also had hose with it that had built-in pressure guage.

I hooked it up to the low pressure side, pressure read zero. I started the truck, turned on the a/c to max and started spraying the can. pressure started building soon, and compressor clicked on. the off. then on. then off......etc.

I added about 3/4 of the 18 oz can. the pressure while running and the a/c on is 47 PSI then the compressor clicks on, slowly drains the pressure down to about 19lbs, at which point the compressor stops, the pressure builds back to 47 PSI, repeat. I thought I must need to add more, and I probably do, but if I turn the truck off the pressure read 125 PSI.

I wanted to make sure that this is O.K.. I havent seen what the pressure is supposed to be if the truck isn't running, but I thought I better ask since I know that the system is sensitive to being over filled.

What should the pressure be while the Compressor is running? how high is the pressure of a correctly charged system when the truck isn't running? could any one check theirs?

thanks again for all your help- I should be driving back in the cool soon!

Brian

**Blee1099** · 07-03-2008, 01:37 PM

Whats the ambient temperature outside?

At around 90, your low pressure should be 25-30 psi and the high side should be 200-220 psi.

*manaen* · 07-03-2008, 01:41 PM

These are all low side pressure readings with the AC running on Max AC

Ambient Temp in F--------Low Side Reading
65 ---------------------- 25-35 psi
70 ---------------------- 35-40 psi
80 ---------------------- 40-50 psi
90 ---------------------- 45-55 psi
95 ---------------------- 50-55 psi
100 ---------------------- 50-55 psi
110 ---------------------- 50-55 psi

that covers the low side readings

**Blee1099** · 07-03-2008, 01:44 PM

Please go out and purchase the right tools.. Those single port ez-fill systems are junk.. Go out get a set of manifold guages and a tap for the cans. Don't forget about the oil for the lube. Charging using one of those ez-fills often leads to overcharging the system.

01eddie · 07-03-2008, 01:56 PM

Thanks for the responses, I don't think that I am fully charged yet.

Unfortunately, the single port cans are all that fits my budget at the moment. I would love to go down and drop 100-200 to get it done correctly, but this is where I am at the moment.

can anyone with functioning A/C tell me what there low pressure side reads when the vehicle is not running?

*manaen* · 07-03-2008, 02:02 PM

It doesn't matter what it reads not running, the system should always be tested and filled with the AC on max. Your pump is shutting off because you don't have enough refrigerant and the low side PSI sensor is dropping below 20psi which turns off your pump. It is always good practice to check the high side pressure as well just to make sure there are no blockages. You should be able to borrow a high side gauge for free from autozone or whatever parts place you have local. You can use the easy fill can you have, just make sure your pressures are good with the system running.

01eddie · 07-03-2008, 04:24 PM

I added the remaining quarter of the 18oz. can and then added a full 12 oz can as well. The compressor now stays on and the pressure with the compressor running is about 39 PSI with an outside air temp of 76 degrees F. The Air now works inside the truck and it definately cooler inside with Air set on Max and the climate controller set at 65 Degrees F.

Thanks again to everyone for all your help. It was an easy fix and only cost about $30. It may not have quite the cooling capacity that it would have if the system have been exausted first, but the air now works and that is WONDERFUL!!

And thanks to Manean for that Pressure/ambient temp table! That thing should be a sticky- I'm sure a lot of people have the same question!

Cobraguy · 07-14-2008, 08:44 AM

Quote:

Originally Posted by manaen

These are all low side pressure readings with the AC running on Max AC

Ambient Temp in F--------Low Side Reading
65 ---------------------- 25-35 psi
70 ---------------------- 35-40 psi
80 ---------------------- 40-50 psi
90 ---------------------- 45-55 psi
95 ---------------------- 50-55 psi
100 ---------------------- 50-55 psi
110 ---------------------- 50-55 psi

that covers the low side readings

If I can't get an R134A low side into the 30's at 95 psi, I would quit. I don't know where that chart came from, but it's horrible. It appears to be one of those manufacturer "cop out" charts. You know...they say, "well, your pressures are where the factory says they should be, so there's nothing we can do about your crappy a/c performance."

*manaen* · 07-14-2008, 10:14 AM

Quote:

If I can't get an R134A low side into the 30's at 95 psi

I assume you mean around 30psi at 95degs?
And you mention nothing about the high pressure readings, which says little about system performance.

Quote:

I don't know where that chart came from, but it's horrible

I will admit the chart is rather old, but it is taken from a ford tech manual. If you have an updated chart please take the time to post it and explain why. It does no good say things like that and then not explain you conclusions. If you have useful information to share, then do so...

Cobraguy · 07-14-2008, 10:32 AM

I don't care where that chart comes from...I stand by my comment about it. It's horrible and any a/c tech that lives by that shouldn't be in the business. C'mon...think about what that is telling you there. Two weeks ago, I serviced a Lincoln LS, a Nissan Frontier, and two Explorers in my garage. Door was open and it was appx105 to 110 degrees outside. All vehicles had outside air thermometers on them and they all read between 95 and 100 in my garage. Every one had low side pressures under 40 psi. Every single one. Duct temps were all in the mid to low 40's. That is with nothing more than a fan blowing in front of the radiator. Going down the highway, they will go lower.

High side was never brought up. so I didn't mention it. But at 95 to 105 degrees, you can see high side pressures way up there...depending on the amount of airflow across the condenser. 225 to 250 psi are not uncommon with the car in a service bay.

I'm not bitching at you in the least. Far from it. That chart is a cop out. I can promise you that you would not live with an a/c system with some of those readings.

omgyouresexy · 06-02-2009, 09:45 AM

I hooked up my manifold set yesterday and recharged with one can. While running, the low side was at 35, high at 230... it was approx 85-90 outside.

I wanted to make sure it wasn't overcharged, or that I didn't need to add more. I think I have a slow leak, but I'm not too sure. I think the pressures while off we're at 110... and I assume I could check the off pressure again a month later and see if it's drop to look for a leak. Sound like an appropriate way to check for a leak?

myf16 · 08-09-2012, 06:27 PM

My high side only goes to about 145 psi. It doesn't blow very cold and the compressor cycles on and off every 20 seconds or so.

This is a 1996 with R134a. Should I just add a 12 oz can of R134a and measure it again?

myf16 · 08-11-2012, 02:15 PM

One can brought me to 36 psi and 225 psi high. It's cold and the compressor stays on at idle. I'm declaring success!

07-03-2008, 01:24 PM	#1
01eddie Wannabe Elite Explorer Grand Forks, North Dakota 2001 Eddie Bauer 5.0 V8 Join Date: Oct 2005 Posts: 20 Vehicle Specs (Original Poster)	What are correct A/C pressures for a charged system? O.K., Here is where I am at the moment.... A/C didn't work, checked to see that compressor would still click on- it did. Bought a can of "EZ Chill" 134a for $18 at Wally world. came in a tall can with lubricant added and leak sealer. also had hose with it that had built-in pressure guage. I hooked it up to the low pressure side, pressure read zero. I started the truck, turned on the a/c to max and started spraying the can. pressure started building soon, and compressor clicked on. the off. then on. then off......etc. I added about 3/4 of the 18 oz can. the pressure while running and the a/c on is 47 PSI then the compressor clicks on, slowly drains the pressure down to about 19lbs, at which point the compressor stops, the pressure builds back to 47 PSI, repeat. I thought I must need to add more, and I probably do, but if I turn the truck off the pressure read 125 PSI. I wanted to make sure that this is O.K.. I havent seen what the pressure is supposed to be if the truck isn't running, but I thought I better ask since I know that the system is sensitive to being over filled. What should the pressure be while the Compressor is running? how high is the pressure of a correctly charged system when the truck isn't running? could any one check theirs? thanks again for all your help- I should be driving back in the cool soon! Brian __________________ My other obsession: www.probetalk.com , and keeping a 1993 Ford Probe GT with 220,000 on the road!

07-03-2008, 01:37 PM	#2
Blee1099 Evil Asian Elkridge, MD 91 Join Date: Mar 2002 Posts: 14,327 Vehicle Specs	Whats the ambient temperature outside? At around 90, your low pressure should be 25-30 psi and the high side should be 200-220 psi. __________________ Decals & Stickers EF Shirts EF Pullover Hoodies EF Zip Up Hoodies EF Travel Coffee Mugs Buy Any 2 and get 2nd half off Bottoms Up Rock Racing

07-03-2008, 01:41 PM	#3
manaen Xterra Forum Member Clear Spring, MD 2011 Xterra Pro-4X Join Date: Feb 2007 Posts: 2,835 Vehicle Specs	These are all low side pressure readings with the AC running on Max AC Ambient Temp in F--------Low Side Reading 65 ---------------------- 25-35 psi 70 ---------------------- 35-40 psi 80 ---------------------- 40-50 psi 90 ---------------------- 45-55 psi 95 ---------------------- 50-55 psi 100 ---------------------- 50-55 psi 110 ---------------------- 50-55 psi that covers the low side readings __________________ Rusty... 2001 Mounty 4x4 4.0 SOHC 4.10's 180K miles Current Mods: replacement Engine, TT, Shackle, AAL, Tranny Cooler, Exhaust, Transgo, Air shocks, ATF Temp & PSI ga., Ext Tranny Filter, UD Pulley, E-Fan, BW EPC, Custom Bumper, Body Lift

07-03-2008, 01:44 PM	#4
Blee1099 Evil Asian Elkridge, MD 91 Join Date: Mar 2002 Posts: 14,327 Vehicle Specs	Please go out and purchase the right tools.. Those single port ez-fill systems are junk.. Go out get a set of manifold guages and a tap for the cans. Don't forget about the oil for the lube. Charging using one of those ez-fills often leads to overcharging the system. __________________ Decals & Stickers EF Shirts EF Pullover Hoodies EF Zip Up Hoodies EF Travel Coffee Mugs Buy Any 2 and get 2nd half off Bottoms Up Rock Racing

07-03-2008, 01:56 PM	#5
01eddie Wannabe Elite Explorer Grand Forks, North Dakota 2001 Eddie Bauer 5.0 V8 Join Date: Oct 2005 Posts: 20 Vehicle Specs (Original Poster)	Thanks for the responses, I don't think that I am fully charged yet. Unfortunately, the single port cans are all that fits my budget at the moment. I would love to go down and drop 100-200 to get it done correctly, but this is where I am at the moment. can anyone with functioning A/C tell me what there low pressure side reads when the vehicle is not running? __________________ My other obsession: www.probetalk.com , and keeping a 1993 Ford Probe GT with 220,000 on the road!

07-03-2008, 02:02 PM	#6
manaen Xterra Forum Member Clear Spring, MD 2011 Xterra Pro-4X Join Date: Feb 2007 Posts: 2,835 Vehicle Specs	It doesn't matter what it reads not running, the system should always be tested and filled with the AC on max. Your pump is shutting off because you don't have enough refrigerant and the low side PSI sensor is dropping below 20psi which turns off your pump. It is always good practice to check the high side pressure as well just to make sure there are no blockages. You should be able to borrow a high side gauge for free from autozone or whatever parts place you have local. You can use the easy fill can you have, just make sure your pressures are good with the system running. __________________ Rusty... 2001 Mounty 4x4 4.0 SOHC 4.10's 180K miles Current Mods: replacement Engine, TT, Shackle, AAL, Tranny Cooler, Exhaust, Transgo, Air shocks, ATF Temp & PSI ga., Ext Tranny Filter, UD Pulley, E-Fan, BW EPC, Custom Bumper, Body Lift

07-03-2008, 04:24 PM	#7
01eddie Wannabe Elite Explorer Grand Forks, North Dakota 2001 Eddie Bauer 5.0 V8 Join Date: Oct 2005 Posts: 20 Vehicle Specs (Original Poster)	I added the remaining quarter of the 18oz. can and then added a full 12 oz can as well. The compressor now stays on and the pressure with the compressor running is about 39 PSI with an outside air temp of 76 degrees F. The Air now works inside the truck and it definately cooler inside with Air set on Max and the climate controller set at 65 Degrees F. Thanks again to everyone for all your help. It was an easy fix and only cost about $30. It may not have quite the cooling capacity that it would have if the system have been exausted first, but the air now works and that is WONDERFUL!! And thanks to Manean for that Pressure/ambient temp table! That thing should be a sticky- I'm sure a lot of people have the same question! __________________ My other obsession: www.probetalk.com , and keeping a 1993 Ford Probe GT with 220,000 on the road! Last edited by 01eddie; 07-04-2008 at 12:43 PM. Reason: I am a poor spellr

06-02-2009, 09:45 AM	#11
omgyouresexy Wannabe Elite Explorer Raleigh, NC '99 Eddie Bauer Join Date: Jan 2009 Posts: 45 Vehicle Specs	I hooked up my manifold set yesterday and recharged with one can. While running, the low side was at 35, high at 230... it was approx 85-90 outside. I wanted to make sure it wasn't overcharged, or that I didn't need to add more. I think I have a slow leak, but I'm not too sure. I think the pressures while off we're at 110... and I assume I could check the off pressure again a month later and see if it's drop to look for a leak. Sound like an appropriate way to check for a leak? __________________ '99 Explorer EB - 4.0 SOHC

08-09-2012, 06:27 PM	#12
myf16 Wannabe Elite Explorer northern California 96 Explorer XLT 4WD Join Date: Jul 2012 Posts: 36 Vehicle Specs	My high side only goes to about 145 psi. It doesn't blow very cold and the compressor cycles on and off every 20 seconds or so. This is a 1996 with R134a. Should I just add a 12 oz can of R134a and measure it again?

08-11-2012, 02:15 PM	#13
myf16 Wannabe Elite Explorer northern California 96 Explorer XLT 4WD Join Date: Jul 2012 Posts: 36 Vehicle Specs	One can brought me to 36 psi and 225 psi high. It's cold and the compressor stays on at idle. I'm declaring success!