I have a 2005 Honda Accord V6 which has not really cooled very well this summer. Its still cold, just not as cold as it was last summer and before. I bought some refrigerant with a gauge and it registered 35 lbs when the clutch was engaged. I charged it to 45 lbs, but then the clutch disengaged and it jumped to 55 lbs. The clutch then began engaging and disengaging every 5 - 10 seconds and the pressure would jump between 45 and 55 lbs or so as this was happening. Did I screw up anything or is this normal? Is it charged properly or overcharged?
A/C charging question...
- Thread starter cwing6
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I would say that 35 pounds would be about right depending on the outside air temperature when you checked it.
When one does add refrigerant it is important to purge the hose of any air because you don't want air or moisture in the system.
If your vehicle had a cabin air filter I would check that to see if it needs changing.
Your system is overcharged.
You can find some pressure temperature charts on the internet for R 134A.
When one does add refrigerant it is important to purge the hose of any air because you don't want air or moisture in the system.
If your vehicle had a cabin air filter I would check that to see if it needs changing.
Your system is overcharged.
You can find some pressure temperature charts on the internet for R 134A.
System is dramatically overcharged now - take it to a professional asap.
If the compressor is cycling like you say it is, then yes, it's likely overcharged, given the original symptom of still cold, but not as cold.
Take my word - I killed the A/C in my car from over charging because I thought the system wasn't cooling like it should.
Take my word - I killed the A/C in my car from over charging because I thought the system wasn't cooling like it should.
You can't judge the correct fill of many current A/C systems by the low-side pressure. By the time the pressure rises, the system is overfilled.
The correct way to fill is evacuating the system, and refilling by weight. That why shops have either gotten out of A/C service, and bought elaborate recovery/refill machines. The machines automatically empty the system, separate the oil when extracting, measure the removed refrigerant (for diagnostic and billing purposes), and refill with the manufacturer specified amount.
This is difficult to reproduce at home. For one thing, oil-less transfer pumps are much more expensive than oil-bath vacuum pumps that empty to the atmosphere.
The only simple solution is to not top off the system until the A/C is over 10 years old, and it's definitely weak (but still cooling, not empty). Then add only one small can, which should restore most of the cooling but still be safely under-filled. Why a decade? Because a good system will leak 0.5-2.0 ounces a year. If the system fill is less than a decade old, it's less likely a refrigerant fill quantity problem.
A friend and I refilled his R134a A/C system today. His Audi needed it's third compressor in as many years, and we decided that the previous dealer service was too sloppy to repeat (missing bolt, incorrectly installed bracket, misrouted wiring).
We recovered some of the R134a into a pressure tank (AKA 'empty propane bottle'). We first pulled a vacuum on the hoses and tank. We then shut off the vacuum pump hose, immersed the tank into ice water, and opened the valve to the system. After 20-30 minutes, most of the refrigerant had boiled from the car and condensed into the tank. The remaining R134a, all gas, had to be vented before we installed the new compressor. A transfer pump could have saved that last bit, perhaps 0.5 ounce of gas.
When refilling we simply put the new cans on a kitchen scale to know how much was added.
The correct way to fill is evacuating the system, and refilling by weight. That why shops have either gotten out of A/C service, and bought elaborate recovery/refill machines. The machines automatically empty the system, separate the oil when extracting, measure the removed refrigerant (for diagnostic and billing purposes), and refill with the manufacturer specified amount.
This is difficult to reproduce at home. For one thing, oil-less transfer pumps are much more expensive than oil-bath vacuum pumps that empty to the atmosphere.
The only simple solution is to not top off the system until the A/C is over 10 years old, and it's definitely weak (but still cooling, not empty). Then add only one small can, which should restore most of the cooling but still be safely under-filled. Why a decade? Because a good system will leak 0.5-2.0 ounces a year. If the system fill is less than a decade old, it's less likely a refrigerant fill quantity problem.
A friend and I refilled his R134a A/C system today. His Audi needed it's third compressor in as many years, and we decided that the previous dealer service was too sloppy to repeat (missing bolt, incorrectly installed bracket, misrouted wiring).
We recovered some of the R134a into a pressure tank (AKA 'empty propane bottle'). We first pulled a vacuum on the hoses and tank. We then shut off the vacuum pump hose, immersed the tank into ice water, and opened the valve to the system. After 20-30 minutes, most of the refrigerant had boiled from the car and condensed into the tank. The remaining R134a, all gas, had to be vented before we installed the new compressor. A transfer pump could have saved that last bit, perhaps 0.5 ounce of gas.
When refilling we simply put the new cans on a kitchen scale to know how much was added.
Couple of more questions....
I re-measured the low pressure this evening and its about 28 lbs at 70 degrees. Could this mean things are OK? Is there any mechanism in the a/c system to prevent overcharging?
The can I used contained 18 oz. and I am going to estimate that I used 3-4 oz. max as the can still filled full when I was done. Only held trigger about 5 - 10 seconds max to move the pressure from 35 to 45 on the can's gage (at 90 degrees temp).
I greatly appreciate everyone's input as I am a newbie in dealing with a/c issues.
I re-measured the low pressure this evening and its about 28 lbs at 70 degrees. Could this mean things are OK? Is there any mechanism in the a/c system to prevent overcharging?
The can I used contained 18 oz. and I am going to estimate that I used 3-4 oz. max as the can still filled full when I was done. Only held trigger about 5 - 10 seconds max to move the pressure from 35 to 45 on the can's gage (at 90 degrees temp).
I greatly appreciate everyone's input as I am a newbie in dealing with a/c issues.
I agree with DJB. I don't care what a temperature/pressure chart says or what the instructions on a doitcherselfer kit say- you CAN NOT properly charge an ac system by watching the low side pressure. Charging by pressure alone is an iffy proposition even if you have a proper manifold gauge set (with both high and low side gauges). Even then, you'd better be familiar with the particular vehicle in question... and even THEN it's only an educated guess if you're going by pressure & temperature.
The only way to properly charge an ac system and KNOW it's correct is to do it by weight. You can do this with a big can and a scale... or you can add up small cans. Either way, you have to charge with a KNOWN quantity. Otherwise you're only guessing, and many ac systems have been damaged this way.
This is difficult for the doityourselfer, for obvious reasons. Not many people have a recovery maching, vacuum pump, and scale laying around. Some of this can be improvised- but you have to know what you're doing.
The only way to properly charge an ac system and KNOW it's correct is to do it by weight. You can do this with a big can and a scale... or you can add up small cans. Either way, you have to charge with a KNOWN quantity. Otherwise you're only guessing, and many ac systems have been damaged this way.
This is difficult for the doityourselfer, for obvious reasons. Not many people have a recovery maching, vacuum pump, and scale laying around. Some of this can be improvised- but you have to know what you're doing.
Originally Posted By: cwing6
Couple of more questions....
I re-measured the low pressure this evening and its about 28 lbs at 70 degrees. Could this mean things are OK? Is there any mechanism in the a/c system to prevent overcharging?
The can I used contained 18 oz. and I am going to estimate that I used 3-4 oz. max as the can still filled full when I was done. Only held trigger about 5 - 10 seconds max to move the pressure from 35 to 45 on the can's gage (at 90 degrees temp).
I greatly appreciate everyone's input as I am a newbie in dealing with a/c issues.
No, there is no mechanism to prevent overcharging. But you vehicle does likely have a high pressure cutoff switch that disengages the compressor clutch when high side pressure gets too high. This is likely the cause of the frequent clutch cycling the you're seeing- high side pressure is too high, causing the clutch to temporarily disengage. This will keep hoses from blowing, and will protect your compressor to SOME extent. But continuing to run an ac system under these conditions will likely kill the compressor due to the increased heat and pressure.
Your low side pressure has gone down for no reason other than the fact that it's cooler outside. All automotive a/c systems cycle the clutch, control the compressor displacement, or control the expansion valve (depending on what sort of system we're talking about) based solely on low side pressure and/or temperature. Now that the temp is cooler outside and your high side is no longer exceeding max pressure... the system is regulating low side pressure normally. And your system will continue to operate normally so long as the outside temp remains relatively low. But as soon as it gets hot outside- your overcharged system will start cutting out the compressor clutch again, and will not cool properly.
One way or another, you need to get the system charged to the proper level. It won't cool properly or be reliable 'til you do that.
Couple of more questions....
I re-measured the low pressure this evening and its about 28 lbs at 70 degrees. Could this mean things are OK? Is there any mechanism in the a/c system to prevent overcharging?
The can I used contained 18 oz. and I am going to estimate that I used 3-4 oz. max as the can still filled full when I was done. Only held trigger about 5 - 10 seconds max to move the pressure from 35 to 45 on the can's gage (at 90 degrees temp).
I greatly appreciate everyone's input as I am a newbie in dealing with a/c issues.
No, there is no mechanism to prevent overcharging. But you vehicle does likely have a high pressure cutoff switch that disengages the compressor clutch when high side pressure gets too high. This is likely the cause of the frequent clutch cycling the you're seeing- high side pressure is too high, causing the clutch to temporarily disengage. This will keep hoses from blowing, and will protect your compressor to SOME extent. But continuing to run an ac system under these conditions will likely kill the compressor due to the increased heat and pressure.
Your low side pressure has gone down for no reason other than the fact that it's cooler outside. All automotive a/c systems cycle the clutch, control the compressor displacement, or control the expansion valve (depending on what sort of system we're talking about) based solely on low side pressure and/or temperature. Now that the temp is cooler outside and your high side is no longer exceeding max pressure... the system is regulating low side pressure normally. And your system will continue to operate normally so long as the outside temp remains relatively low. But as soon as it gets hot outside- your overcharged system will start cutting out the compressor clutch again, and will not cool properly.
One way or another, you need to get the system charged to the proper level. It won't cool properly or be reliable 'til you do that.
To understand why pressure gauges won't tell you the proper fill level you have to understand the car's A/C system and how liquids boil.
Most current car A/C systems have receiver/drier cans. This is the system reservoir. Think of this as a cup with a straw to the bottom, refilling from a drink dispenser that is spitting out mist. You can get little hint of how full the cup is by how hard you have to suck on the straw, but it's easy to be wrong. And if you guess wrong, you are either sucking mist (not thirst quenching, and leads to belching) or the cup overflows (a big mess). This is just like measuring the system pressure -- you can't really tell how much is in there unless the pressure is obviously too low (empty) or too high (overfull).
A analogy for the system pressure is boiling water. You can't tell how much water you have in a pot by measuring its temperature, or listing to whistle of a teakettle. As long as you have sufficient water in the pot, it will boil at the same temperature. Only at the very end, with just a thin layer of water, will the temperature shoot up / whistle increase in pitch.
So why have gauges at all? For gauge sets, it's mostly about having the valves. without the valves you couldn't change from pulling a vacuum to filling the system. You only use the gauges for diagnostics, and for confirmation that you have the valves set correctly. For fill hoses, the gauge only tells you when things have gone badly -- overfilled, a massive leak, or that there are multiple gases in the system.
Most current car A/C systems have receiver/drier cans. This is the system reservoir. Think of this as a cup with a straw to the bottom, refilling from a drink dispenser that is spitting out mist. You can get little hint of how full the cup is by how hard you have to suck on the straw, but it's easy to be wrong. And if you guess wrong, you are either sucking mist (not thirst quenching, and leads to belching) or the cup overflows (a big mess). This is just like measuring the system pressure -- you can't really tell how much is in there unless the pressure is obviously too low (empty) or too high (overfull).
A analogy for the system pressure is boiling water. You can't tell how much water you have in a pot by measuring its temperature, or listing to whistle of a teakettle. As long as you have sufficient water in the pot, it will boil at the same temperature. Only at the very end, with just a thin layer of water, will the temperature shoot up / whistle increase in pitch.
So why have gauges at all? For gauge sets, it's mostly about having the valves. without the valves you couldn't change from pulling a vacuum to filling the system. You only use the gauges for diagnostics, and for confirmation that you have the valves set correctly. For fill hoses, the gauge only tells you when things have gone badly -- overfilled, a massive leak, or that there are multiple gases in the system.
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Originally Posted By: onion
I agree with DJB. I don't care what a temperature/pressure chart says or what the instructions on a doitcherselfer kit say- you CAN NOT properly charge an ac system by watching the low side pressure. Charging by pressure alone is an iffy proposition even if you have a proper manifold gauge set (with both high and low side gauges). Even then, you'd better be familiar with the particular vehicle in question... and even THEN it's only an educated guess if you're going by pressure & temperature.
The only way to properly charge an ac system and KNOW it's correct is to do it by weight. You can do this with a big can and a scale... or you can add up small cans. Either way, you have to charge with a KNOWN quantity. Otherwise you're only guessing, and many ac systems have been damaged this way.
This is difficult for the doityourselfer, for obvious reasons. Not many people have a recovery maching, vacuum pump, and scale laying around. Some of this can be improvised- but you have to know what you're doing.
X2. W/o a high side guage your low side guage is totally useless. Get me a high side pressure reading and ambient temp I can tell you if your overcharged or not. Your Honda has a very small system and 1 or 2 oz over or undercharged is a problem.
You should have checked your heater valve before adding any refrigerant. Honda heater valves often fail and allow hot air to mix with the cold AC air. I bet that was your original problem.
I agree with DJB. I don't care what a temperature/pressure chart says or what the instructions on a doitcherselfer kit say- you CAN NOT properly charge an ac system by watching the low side pressure. Charging by pressure alone is an iffy proposition even if you have a proper manifold gauge set (with both high and low side gauges). Even then, you'd better be familiar with the particular vehicle in question... and even THEN it's only an educated guess if you're going by pressure & temperature.
The only way to properly charge an ac system and KNOW it's correct is to do it by weight. You can do this with a big can and a scale... or you can add up small cans. Either way, you have to charge with a KNOWN quantity. Otherwise you're only guessing, and many ac systems have been damaged this way.
This is difficult for the doityourselfer, for obvious reasons. Not many people have a recovery maching, vacuum pump, and scale laying around. Some of this can be improvised- but you have to know what you're doing.
X2. W/o a high side guage your low side guage is totally useless. Get me a high side pressure reading and ambient temp I can tell you if your overcharged or not. Your Honda has a very small system and 1 or 2 oz over or undercharged is a problem.
You should have checked your heater valve before adding any refrigerant. Honda heater valves often fail and allow hot air to mix with the cold AC air. I bet that was your original problem.
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A low side gauge can be very useful.
A good first check for most modern R134a systems is after an overnight sit. At about 75 F, the system should read 75 rest pressure. At 85F about 90. This is the static rest pressure, and is a good first check.
The low side cycles[most systems]. From about 25 to 45 .
A bit too little is better than a bit overfilled, with R134a.
A good first check for most modern R134a systems is after an overnight sit. At about 75 F, the system should read 75 rest pressure. At 85F about 90. This is the static rest pressure, and is a good first check.
The low side cycles[most systems]. From about 25 to 45 .
A bit too little is better than a bit overfilled, with R134a.
I filled my 1999 Buick's A/C with half a large can of r134a, and the A/C will freeze you now. This appears to be an older car leaking refrigerant that needed a top-off.
They all leak, eventually.
You have received some good suggestions. MechTech2 is quite correct in stating that the system works better (colder) when it is slightly undercharged. This is especially true when using r12 but applies to 134a also. Regards. John--Las Vegas.
Originally Posted By: sciphi
I filled my 1999 Buick's A/C with half a large can of r134a, and the A/C will freeze you now. This appears to be an older car leaking refrigerant that needed a top-off.
Added a full 12 oz to my Saturn and now it cools great. But there's probably a leak somewhere, so don't repeat what I did.
I filled my 1999 Buick's A/C with half a large can of r134a, and the A/C will freeze you now. This appears to be an older car leaking refrigerant that needed a top-off.
Added a full 12 oz to my Saturn and now it cools great. But there's probably a leak somewhere, so don't repeat what I did.
Mine's not leaking, just was a little low. Still cools great, no funny noises or odd behavior. I guess it's expected on an 11 year old car that some freon will escape.
Originally Posted By: sciphi
Mine's not leaking, just was a little low. Still cools great, no funny noises or odd behavior. I guess it's expected on an 11 year old car that some freon will escape.
I would say if its low, you have a leak...
Mine's not leaking, just was a little low. Still cools great, no funny noises or odd behavior. I guess it's expected on an 11 year old car that some freon will escape.
I would say if its low, you have a leak...
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