recharging the A/C
08-06-2004, 04:54 PM
#1
Senior Member
Thread Starter
Join Date: Feb 2004
Posts: 207
recharging the A/C
So I am at Walmart today, in the car section, and I noticed the freon(spellin?) and the charging attachment/hose. I talked to a guy there, wasnt a mechanic or anything, and he said he's done it before and its easy. He said you just plug up everything and fill it up according to the meter attached to the hose apparatus.
So is it this easy? Cause I always thought a mechanic had to do this?
Anyone out there recharged their freon for the Air Conditioning?
If so, where can I find out which kind of freon to use and is there a WRITE-UP out there?
THanks
So is it this easy? Cause I always thought a mechanic had to do this?
Anyone out there recharged their freon for the Air Conditioning?
If so, where can I find out which kind of freon to use and is there a WRITE-UP out there?
THanks
08-17-2004, 09:31 PM
#2
Senior Member
Join Date: Aug 2000
Posts: 351
First, R-12 (freon) is no longer sold to the general public. What Walmart has is R-134a. Your Maxima uses R-134a.
Second, you need to figure out if you really need to recharge the system. Buy a good pressure gauge. The one I got has adapters for both high and low side ports, and a valve for the recharge can. You'll need to find somebody that has a service manual. There's a chart in there that has pressures for corresponding ambient temperatures.
Third, once you've decided you do need to recharge, buy a small can of R-134a with stop-leak, "cold booster", and PAG oil - all in one can. Connect the can through the gauge assembly to the low side port only. With the engine running and AC turned on, hold the can upside down and open the valve. Assuming the compressor is running, the refrigerant will spray in through the low side port.
Last, when the can has emptied, disconnect and go for a ride.
If the AC works for a while but stops, and you can feel the compressor cycle on-off repeatedly, you've overcharged the system. Use a small screwdriver to let some R-134a out of the low side until the compressor stays on all the time.
Second, you need to figure out if you really need to recharge the system. Buy a good pressure gauge. The one I got has adapters for both high and low side ports, and a valve for the recharge can. You'll need to find somebody that has a service manual. There's a chart in there that has pressures for corresponding ambient temperatures.
Third, once you've decided you do need to recharge, buy a small can of R-134a with stop-leak, "cold booster", and PAG oil - all in one can. Connect the can through the gauge assembly to the low side port only. With the engine running and AC turned on, hold the can upside down and open the valve. Assuming the compressor is running, the refrigerant will spray in through the low side port.
Last, when the can has emptied, disconnect and go for a ride.
If the AC works for a while but stops, and you can feel the compressor cycle on-off repeatedly, you've overcharged the system. Use a small screwdriver to let some R-134a out of the low side until the compressor stays on all the time.
08-19-2004, 09:54 PM
#3
Senior Member
Thread Starter
Join Date: Feb 2004
Posts: 207
Originally Posted by Sly
Second, you need to figure out if you really need to recharge the system. Buy a good pressure gauge. The one I got has adapters for both high and low side ports, and a valve for the recharge can. You'll need to find somebody that has a service manual. There's a chart in there that has pressures for corresponding ambient temperatures.
When you say, "to figure out if you really need to recharge the system..."
The pressure guage wont tell you if your low when you hook it up?
and
The pressure guages I've seen have a low, good and overfill zone on it. Cant I use this to determine how much to add without adding the entire can then checking by your method then letting some out?
Thanks
08-19-2004, 10:56 PM
#4
Supporting Maxima.org Member
Join Date: May 2003
Posts: 268
Originally Posted by PTP
When you say, "to figure out if you really need to recharge the system..."
The pressure guage wont tell you if your low when you hook it up?
and
The pressure guages I've seen have a low, good and overfill zone on it. Cant I use this to determine how much to add without adding the entire can then checking by your method then letting some out?
Thanks
The pressure guage wont tell you if your low when you hook it up?
and
The pressure guages I've seen have a low, good and overfill zone on it. Cant I use this to determine how much to add without adding the entire can then checking by your method then letting some out?
Thanks
If I were you I would buy the can with all the stuff you need; leak seal, r-134a, and boost...plus the built in guage. Its worth the 20.00 bucks for the can. You probably won't use the entire can because its the same as using 2 of the regular size cans. I used it on my brothers truck. Just put on the low side..turn air condition on HIGH MAX...and then see where the guage is....if its low just sqeeze the button on the can until the guage reads normal..Works like a charm!!!
08-20-2004, 08:41 AM
#5
Senior Member
Thread Starter
Join Date: Feb 2004
Posts: 207
PICs of the line
So just to be sure this is the LOW side of the AC recharge line right?
http://ahsan.fotopic.net/p6875084.html
http://ahsan.fotopic.net/p6875084.html
http://ahsan.fotopic.net/p6875084.html
http://ahsan.fotopic.net/p6875084.html
08-20-2004, 11:57 AM
#6
Supporting Maxima.org Member
Join Date: Oct 2002
Posts: 109
Originally Posted by ptp
The pressure guage wont tell you if your low when you hook it up?
and
The pressure guages I've seen have a low, good and overfill zone on it. Cant I use this to determine how much to add without adding the entire can then checking by your method then letting some out?
and
The pressure guages I've seen have a low, good and overfill zone on it. Cant I use this to determine how much to add without adding the entire can then checking by your method then letting some out?
While this control is not perfect (the evaporator pressure will rise and fall somewhat according to the a/c heat load and the engine speed) it does mean that the evaporator pressure is not a reliable guide to the charge level. All it really tells you is whether the compressor is working normally.
If the compressor is cycling on and off (and the ambient is freezing or above) then you have one of two problems: either the system is so low on charge that the low pressure protective cutout is being triggered, or it is so severely overcharged that the high pressure cutout is triggered. (or the pressure sensor itself is bad.)
The only really reliable way to get the right amount of charge is to evacuate the system and then fill it while weighing the amount of refrigerant added. This is what the pro systems do. This service should not be ruinously expensive, though it is more than an impulse buy. ($100, + or -, at an independent shop). (For the old R-12 systems it is much more expensive now.)
That said, you can probably achieve a workable result yourself by monitoring the temperature of the suction line as you (slowly) add refrigerant. Do this on a hot day so that the system has some load on it. If you have the manual a/c, be sure it is not in recirc mode. If you have the auto a/c it will probably switch itself into recirc - therefore open the car windows or doors. The blower should be on high speed. First run the system for a few minutes. Make sure the compressor discharge is hot to the touch - if it is not, then either the system is not working at all, or else the heat load is so low that you should wait for a hotter day before continuing. (Depending on the heat load, the h.p. liquid line coming out of the condenser might be anywhere from ambient to uncomfortably warm, but it should be noticeably less hot than the compressor discharge.) Use the gauge to check the evap. pressure. If it is higher than the normal range, stop, you have bigger problems that you need a pro to fix. If the compressor has been running for a few minutes, the evaporator pressure gauge reads in the normal range or a little below, and the suction line is not cool, it's reasonable to conclude that the system is undercharged. Add a small amount of refrigerant and give it a couple of minutes to stabilize. You can repeat this and you should sense the suction line getting cold. Don't overcharge since that can result in high compressor discharge pressure and a lot of expensive problems - it is better slightly undercharged than overcharged. Also, although a previous poster said to tip the refrigerant can upside down, I think this isn't recommended. You risk sending a slug of liquid into the compressor, which can wreck it. You can put the can in a pan of warm water (no more than about 120 deg. F) to increase the gas flow, but be careful not to add too much. And always be aware that the temperatures in an a/c system need a few minutes to stabilize - make small changes and be patient.
How cool the suction line should be is not easy to say - it depends on a lot of rather complex factors. If the day is a summer day with a dewpoint at least in the mid 60s, and the suction line has condensation on it all the way to the compressor inlet, then your system is probably operating at full capacity. (Don't add any more refrigerant.) In a hot, dry climate you might not see any condensation on the line, but it will be cool to the touch. On a very hot day even in a humid climate, you might also not get condensation. Whatever the temperature is, if the system is fully charged the suction line should be pretty much constant temperature from the evaporator outlet (at the firewall) to the compressor inlet. (Be very careful of your fingers and loose clothing around the belts and radiator fans, and beware that some of the components are very hot and might cause a reflex jump when you touch them.)
Be sure to purge the air out of the charging line before you connect it to the service port.
Some cars have a sight glass at the exit from the condenser, which is a more reliable way to estimate the state of charge. Unfortunately the Maxima's system doesn't have one that I can find.
Also note that, while automotive a/c systems usually leak down slowly over a period of several years, if you car is less than 3 years old and it needs charging, you likely have a bad seal somewhere.
08-25-2012, 09:12 PM
#7
The a/c system on the 2k2/3 (and, I assume the 2k0/1 as well) has a variable-displacement compressor that acts to stabilize the evaporator pressure. The compressor runs all the time when the a/c switch is on and the ambient temperature is above about 23 deg. F. (This is unlike many other cars where the compressor clutch opens and closes in response to evaporator temperature.)
While this control is not perfect (the evaporator pressure will rise and fall somewhat according to the a/c heat load and the engine speed) it does mean that the evaporator pressure is not a reliable guide to the charge level. All it really tells you is whether the compressor is working normally.
If the compressor is cycling on and off (and the ambient is freezing or above) then you have one of two problems: either the system is so low on charge that the low pressure protective cutout is being triggered, or it is so severely overcharged that the high pressure cutout is triggered. (or the pressure sensor itself is bad.)
The only really reliable way to get the right amount of charge is to evacuate the system and then fill it while weighing the amount of refrigerant added. This is what the pro systems do. This service should not be ruinously expensive, though it is more than an impulse buy. ($100, + or -, at an independent shop). (For the old R-12 systems it is much more expensive now.)
That said, you can probably achieve a workable result yourself by monitoring the temperature of the suction line as you (slowly) add refrigerant. Do this on a hot day so that the system has some load on it. If you have the manual a/c, be sure it is not in recirc mode. If you have the auto a/c it will probably switch itself into recirc - therefore open the car windows or doors. The blower should be on high speed. First run the system for a few minutes. Make sure the compressor discharge is hot to the touch - if it is not, then either the system is not working at all, or else the heat load is so low that you should wait for a hotter day before continuing. (Depending on the heat load, the h.p. liquid line coming out of the condenser might be anywhere from ambient to uncomfortably warm, but it should be noticeably less hot than the compressor discharge.) Use the gauge to check the evap. pressure. If it is higher than the normal range, stop, you have bigger problems that you need a pro to fix. If the compressor has been running for a few minutes, the evaporator pressure gauge reads in the normal range or a little below, and the suction line is not cool, it's reasonable to conclude that the system is undercharged. Add a small amount of refrigerant and give it a couple of minutes to stabilize. You can repeat this and you should sense the suction line getting cold. Don't overcharge since that can result in high compressor discharge pressure and a lot of expensive problems - it is better slightly undercharged than overcharged. Also, although a previous poster said to tip the refrigerant can upside down, I think this isn't recommended. You risk sending a slug of liquid into the compressor, which can wreck it. You can put the can in a pan of warm water (no more than about 120 deg. F) to increase the gas flow, but be careful not to add too much. And always be aware that the temperatures in an a/c system need a few minutes to stabilize - make small changes and be patient.
How cool the suction line should be is not easy to say - it depends on a lot of rather complex factors. If the day is a summer day with a dewpoint at least in the mid 60s, and the suction line has condensation on it all the way to the compressor inlet, then your system is probably operating at full capacity. (Don't add any more refrigerant.) In a hot, dry climate you might not see any condensation on the line, but it will be cool to the touch. On a very hot day even in a humid climate, you might also not get condensation. Whatever the temperature is, if the system is fully charged the suction line should be pretty much constant temperature from the evaporator outlet (at the firewall) to the compressor inlet. (Be very careful of your fingers and loose clothing around the belts and radiator fans, and beware that some of the components are very hot and might cause a reflex jump when you touch them.)
Be sure to purge the air out of the charging line before you connect it to the service port.
Some cars have a sight glass at the exit from the condenser, which is a more reliable way to estimate the state of charge. Unfortunately the Maxima's system doesn't have one that I can find.
Also note that, while automotive a/c systems usually leak down slowly over a period of several years, if you car is less than 3 years old and it needs charging, you likely have a bad seal somewhere.
While this control is not perfect (the evaporator pressure will rise and fall somewhat according to the a/c heat load and the engine speed) it does mean that the evaporator pressure is not a reliable guide to the charge level. All it really tells you is whether the compressor is working normally.
If the compressor is cycling on and off (and the ambient is freezing or above) then you have one of two problems: either the system is so low on charge that the low pressure protective cutout is being triggered, or it is so severely overcharged that the high pressure cutout is triggered. (or the pressure sensor itself is bad.)
The only really reliable way to get the right amount of charge is to evacuate the system and then fill it while weighing the amount of refrigerant added. This is what the pro systems do. This service should not be ruinously expensive, though it is more than an impulse buy. ($100, + or -, at an independent shop). (For the old R-12 systems it is much more expensive now.)
That said, you can probably achieve a workable result yourself by monitoring the temperature of the suction line as you (slowly) add refrigerant. Do this on a hot day so that the system has some load on it. If you have the manual a/c, be sure it is not in recirc mode. If you have the auto a/c it will probably switch itself into recirc - therefore open the car windows or doors. The blower should be on high speed. First run the system for a few minutes. Make sure the compressor discharge is hot to the touch - if it is not, then either the system is not working at all, or else the heat load is so low that you should wait for a hotter day before continuing. (Depending on the heat load, the h.p. liquid line coming out of the condenser might be anywhere from ambient to uncomfortably warm, but it should be noticeably less hot than the compressor discharge.) Use the gauge to check the evap. pressure. If it is higher than the normal range, stop, you have bigger problems that you need a pro to fix. If the compressor has been running for a few minutes, the evaporator pressure gauge reads in the normal range or a little below, and the suction line is not cool, it's reasonable to conclude that the system is undercharged. Add a small amount of refrigerant and give it a couple of minutes to stabilize. You can repeat this and you should sense the suction line getting cold. Don't overcharge since that can result in high compressor discharge pressure and a lot of expensive problems - it is better slightly undercharged than overcharged. Also, although a previous poster said to tip the refrigerant can upside down, I think this isn't recommended. You risk sending a slug of liquid into the compressor, which can wreck it. You can put the can in a pan of warm water (no more than about 120 deg. F) to increase the gas flow, but be careful not to add too much. And always be aware that the temperatures in an a/c system need a few minutes to stabilize - make small changes and be patient.
How cool the suction line should be is not easy to say - it depends on a lot of rather complex factors. If the day is a summer day with a dewpoint at least in the mid 60s, and the suction line has condensation on it all the way to the compressor inlet, then your system is probably operating at full capacity. (Don't add any more refrigerant.) In a hot, dry climate you might not see any condensation on the line, but it will be cool to the touch. On a very hot day even in a humid climate, you might also not get condensation. Whatever the temperature is, if the system is fully charged the suction line should be pretty much constant temperature from the evaporator outlet (at the firewall) to the compressor inlet. (Be very careful of your fingers and loose clothing around the belts and radiator fans, and beware that some of the components are very hot and might cause a reflex jump when you touch them.)
Be sure to purge the air out of the charging line before you connect it to the service port.
Some cars have a sight glass at the exit from the condenser, which is a more reliable way to estimate the state of charge. Unfortunately the Maxima's system doesn't have one that I can find.
Also note that, while automotive a/c systems usually leak down slowly over a period of several years, if you car is less than 3 years old and it needs charging, you likely have a bad seal somewhere.
http://static.cargurus.com/images/si...152057931.jpeg
08-25-2012, 09:15 PM
#8
Senior Member
Join Date: Sep 2010
Location: Jacksonville, FL
Posts: 10,349
Would it be possible for you (or anybody) to point out the location of the hoses etc that you mentioned?
http://static.cargurus.com/images/si...152057931.jpeg
http://static.cargurus.com/images/si...152057931.jpeg
The hoses which have the low and high side are easily visible on our cars on the passenger side. Each has a cap, L for low and H for high. Look for the aluminum hardlines.
08-25-2012, 09:30 PM
#9
He says: suction line, compressor discharge, and also, where does the gauge go to measure evap pressure?
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