AC not cold enough
08-12-2013, 09:48 PM
#1
AC not cold enough I'm at a loss here. I replaced almost everything in the a/c system last year. New compressor, accumulator, expansion valve, evap core, and hoses. Ever since then the coldest I can get it is about a 25 degree drop from ambient temp- usually about 20*. Before I replaced it the evap had a small leak and the compressor seals were bad but when charged up it would blow ice cold. Pressures are good- no leaks. Drains good. Fans kick on high speed. Condenser is clean. Blend door is completely closed. Any ideas? It was 95* yesterday and the coldest I could get out of the vents was a hair below 80*. I can't afford to keep driving my truck everyday lol.
08-14-2013, 11:30 AM
#6
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Might have a look at the exit tube from the evap,
if you're not shedding the cold in the airbox then
that line ought to be icing up. If you're not icing
and not throwing cold into the airbox then that says
more like a restriction upstream.
Might check for a difference between initial cooling
throw, and steady-state, like comes from evap icing.
A screwup where the control doesn't know evap temp
can let that happen quick, especially in humid climes.
if you're not shedding the cold in the airbox then
that line ought to be icing up. If you're not icing
and not throwing cold into the airbox then that says
more like a restriction upstream.
Might check for a difference between initial cooling
throw, and steady-state, like comes from evap icing.
A screwup where the control doesn't know evap temp
can let that happen quick, especially in humid climes.
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08-14-2013, 07:47 PM
#8
what type of vacuum pump and gauge did you use? how much of a vacuum did you pull?
i'd be willing to bet you have moisture and/or contamination in there and is why you are getting poor performance. that is very common to happen unless you have good equipment and know the numbers.
going from my book, the system is contaminated if it contains 150ppm or more by weight of a noncondensable gas in an r134a system. to give you an idea a drop of moisture (water) in a system that contains 6 pounds of refrigerant is equivalent to 20 ppm which is too much. your ac system only holds 1.5 lbs. refrigerant is supposed to be moisture free at under 10ppm and the max allowable is 15ppm.
so cleanliness is very important, you don't leave a bottle of pag oil open to collect moisture before injecting it into the system. you don't leave a new accumulator uncapped and exposed to collect moisture inside, and the same for other parts and hoses. otherwise you'll spend that much longer pulling a harder vacuum for longer to get the moisture out.
It's said you need to pull a vacuum down to 700 microns or lower, and ideally to 300 microns and have it hold for a few hours to be sure you get the moisture out of the system. water will boil at 80° at 28.92" or 25400 microns. at 64° 29.32" 15240 microns. like i said the norm is to pull down to around 700 microns at least which is around 29.90". so a lot depends on your gauge and the quality of your vacuum pump. pulling from 28.80" to 29.90" makes all the difference and down below 1000 microns your at thousandths of an inch.
the other thing you may be able to check is static pressure of the system, you have to do it when it's stabilized when the car is off and out of the sun. you take an AC system pressure measurement, and a temperature measurement of the engine bay and metal ac lines with a good thermocouple not an ir gun. you need to be accurate to the degree and sure of the temperature of the refigerant in the AC system. then and look up what the temperature pressure relationship is. if you have air in the system the pressure will be higher than what the chart says. chart for r134a is 75°=83psi 80°=91psi 85=100, 90=109 95=118
i'd be willing to bet you have moisture and/or contamination in there and is why you are getting poor performance. that is very common to happen unless you have good equipment and know the numbers.
going from my book, the system is contaminated if it contains 150ppm or more by weight of a noncondensable gas in an r134a system. to give you an idea a drop of moisture (water) in a system that contains 6 pounds of refrigerant is equivalent to 20 ppm which is too much. your ac system only holds 1.5 lbs. refrigerant is supposed to be moisture free at under 10ppm and the max allowable is 15ppm.
so cleanliness is very important, you don't leave a bottle of pag oil open to collect moisture before injecting it into the system. you don't leave a new accumulator uncapped and exposed to collect moisture inside, and the same for other parts and hoses. otherwise you'll spend that much longer pulling a harder vacuum for longer to get the moisture out.
It's said you need to pull a vacuum down to 700 microns or lower, and ideally to 300 microns and have it hold for a few hours to be sure you get the moisture out of the system. water will boil at 80° at 28.92" or 25400 microns. at 64° 29.32" 15240 microns. like i said the norm is to pull down to around 700 microns at least which is around 29.90". so a lot depends on your gauge and the quality of your vacuum pump. pulling from 28.80" to 29.90" makes all the difference and down below 1000 microns your at thousandths of an inch.
the other thing you may be able to check is static pressure of the system, you have to do it when it's stabilized when the car is off and out of the sun. you take an AC system pressure measurement, and a temperature measurement of the engine bay and metal ac lines with a good thermocouple not an ir gun. you need to be accurate to the degree and sure of the temperature of the refigerant in the AC system. then and look up what the temperature pressure relationship is. if you have air in the system the pressure will be higher than what the chart says. chart for r134a is 75°=83psi 80°=91psi 85=100, 90=109 95=118
Last edited by 1 FMF; 08-14-2013 at 10:34 PM.
08-14-2013, 11:10 PM
#9
Might have a look at the exit tube from the evap,
if you're not shedding the cold in the airbox then
that line ought to be icing up. If you're not icing
and not throwing cold into the airbox then that says
more like a restriction upstream.
Might check for a difference between initial cooling
throw, and steady-state, like comes from evap icing.
A screwup where the control doesn't know evap temp
can let that happen quick, especially in humid climes.
if you're not shedding the cold in the airbox then
that line ought to be icing up. If you're not icing
and not throwing cold into the airbox then that says
more like a restriction upstream.
Might check for a difference between initial cooling
throw, and steady-state, like comes from evap icing.
A screwup where the control doesn't know evap temp
can let that happen quick, especially in humid climes.
08-14-2013, 11:29 PM
#10
what type of vacuum pump and gauge did you use? how much of a vacuum did you pull?
i'd be willing to bet you have moisture and/or contamination in there and is why you are getting poor performance. that is very common to happen unless you have good equipment and know the numbers.
going from my book, the system is contaminated if it contains 150ppm or more by weight of a noncondensable gas in an r134a system. to give you an idea a drop of moisture (water) in a system that contains 6 pounds of refrigerant is equivalent to 20 ppm which is too much. your ac system only holds 1.5 lbs. refrigerant is supposed to be moisture free at under 10ppm and the max allowable is 15ppm.
so cleanliness is very important, you don't leave a bottle of pag oil open to collect moisture before injecting it into the system. you don't leave a new accumulator uncapped and exposed to collect moisture inside, and the same for other parts and hoses. otherwise you'll spend that much longer pulling a harder vacuum for longer to get the moisture out.
It's said you need to pull a vacuum down to 700 microns or lower, and ideally to 300 microns and have it hold for a few hours to be sure you get the moisture out of the system. water will boil at 80° at 28.92" or 25400 microns. at 64° 29.32" 15240 microns. like i said the norm is to pull down to around 700 microns at least which is around 29.90". so a lot depends on your gauge and the quality of your vacuum pump. pulling from 28.80" to 29.90" makes all the difference and down below 1000 microns your at thousandths of an inch.
the other thing you may be able to check is static pressure of the system, you have to do it when it's stabilized when the car is off and out of the sun. you take an AC system pressure measurement, and a temperature measurement of the engine bay and metal ac lines with a good thermocouple not an ir gun. you need to be accurate to the degree and sure of the temperature of the refigerant in the AC system. then and look up what the temperature pressure relationship is. if you have air in the system the pressure will be higher than what the chart says. chart for r134a is 75°=83psi 80°=91psi 85=100, 90=109 95=118
i'd be willing to bet you have moisture and/or contamination in there and is why you are getting poor performance. that is very common to happen unless you have good equipment and know the numbers.
going from my book, the system is contaminated if it contains 150ppm or more by weight of a noncondensable gas in an r134a system. to give you an idea a drop of moisture (water) in a system that contains 6 pounds of refrigerant is equivalent to 20 ppm which is too much. your ac system only holds 1.5 lbs. refrigerant is supposed to be moisture free at under 10ppm and the max allowable is 15ppm.
so cleanliness is very important, you don't leave a bottle of pag oil open to collect moisture before injecting it into the system. you don't leave a new accumulator uncapped and exposed to collect moisture inside, and the same for other parts and hoses. otherwise you'll spend that much longer pulling a harder vacuum for longer to get the moisture out.
It's said you need to pull a vacuum down to 700 microns or lower, and ideally to 300 microns and have it hold for a few hours to be sure you get the moisture out of the system. water will boil at 80° at 28.92" or 25400 microns. at 64° 29.32" 15240 microns. like i said the norm is to pull down to around 700 microns at least which is around 29.90". so a lot depends on your gauge and the quality of your vacuum pump. pulling from 28.80" to 29.90" makes all the difference and down below 1000 microns your at thousandths of an inch.
the other thing you may be able to check is static pressure of the system, you have to do it when it's stabilized when the car is off and out of the sun. you take an AC system pressure measurement, and a temperature measurement of the engine bay and metal ac lines with a good thermocouple not an ir gun. you need to be accurate to the degree and sure of the temperature of the refigerant in the AC system. then and look up what the temperature pressure relationship is. if you have air in the system the pressure will be higher than what the chart says. chart for r134a is 75°=83psi 80°=91psi 85=100, 90=109 95=118
08-24-2013, 02:06 PM
#13
Well apparently it's not the condenser. Installed this morning. Vac'd down for 2 1/2 hours. Humidity 60%, temp 98* in the shade, coldest a/c was 78*. FML. Pressures are 40 on low side and 300 on high side. Put in 2 1/2 12 oz cans. Temp never got below 78 when charging. High side seems a little higher than it should be. No icing anywhere I could see.
08-26-2013, 04:02 PM
#14
Finally have the answer. I took it to a friend of mine's shop because I was out of ideas. They found that the cover that goes over the heater core wasn't sealed around it- so there was hot air leaking around it and that was being sucked into the a/c. Sealed the heater core box and now I have 55* a/c 
.
. 
09-02-2013, 01:19 PM
#16
Finally have the answer. I took it to a friend of mine's shop because I was out of ideas. They found that the cover that goes over the heater core wasn't sealed around it- so there was hot air leaking around it and that was being sucked into the a/c. Sealed the heater core box and now I have 55* a/c .
.
09-02-2013, 09:07 PM
#18
I'll bet that's my trouble too. Everything checks out good in the AC system but I only get aprox 20 degree drop if i'm lucky. Can you tell me a little more and where the cover is? I assume inside the car under the dash? I found the foam seal outside on the evap tubes was out of place shrunk but that was only letting cold air out.