Some cars cycle the fan as needed. Will turn it on around 300 and off around 200 then repeat over and over.
134a high side pressure over 300
- Thread starter i6pwr
- Start date
Update, today the ambient is 76 deg, I have about 75 psi so close enough
At idle the fans were spinning faster today, LH was 2350 RPM, RH was 2660 RPM. I had 32/105 PSI at idle and 48 deg at vents, at 2000 RPM, I had 25/140 PSI and 42 deg at vents, doors open, fan on HI, no recirc.
I sprayed the condenser with water at idle and the high side went from 125 PSI to 100 PSI.
Condenser is free of debris but not shiny.
At idle the fans were spinning faster today, LH was 2350 RPM, RH was 2660 RPM. I had 32/105 PSI at idle and 48 deg at vents, at 2000 RPM, I had 25/140 PSI and 42 deg at vents, doors open, fan on HI, no recirc.
I sprayed the condenser with water at idle and the high side went from 125 PSI to 100 PSI.
Condenser is free of debris but not shiny.
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Evaporator can be limited to 32 F because of ice building up. Especially if ambient humidity is high, but still in general, unless the ambient is extremely dry < 20 %, then the temp of the evaporator can easily be limited.
Expect a Delta of 15 F for any good amount of heat transfer. That plus 32 means if the output air is anywhere around 47 F it working pretty good.
With all windows open, Ac cab vents not on recirculate, cab fan(s) on max, and an ambient of 80 F and the engine held at 2,000 RPM, charge gas only into the low side until high side shows 250 psi. For at least an instant. If the can gets frost on the outside while charging, warm it some. You dont have to add more and have it stay at 250. As long at it reached 250 for a few seconds then its charged enough. Close can feed, then slowly turn high side connection valve off at vehicle connection, but leave the hoses connected. Then slowly drain the refrigeranent and oil that has accumulated in the lines and gauges into the low side. Let it run a while so the low side sucks refrigerant from any oil still in the hoses and gsuges. Then close the low side valve at the vehicle connection. Wearing safety glasses disconnect both hoses from the vehicle.
After both hoses are disconncted from the vehicle, depressurize the hoses and gauges but expect some oil from the hoses and some refrigerant, so still be wearing safety glasses and dont let oil get on anything you dont want oil on. Connect vehicle side of hoses to storage connections on gauge set.
Good to go.
Expect a Delta of 15 F for any good amount of heat transfer. That plus 32 means if the output air is anywhere around 47 F it working pretty good.
With all windows open, Ac cab vents not on recirculate, cab fan(s) on max, and an ambient of 80 F and the engine held at 2,000 RPM, charge gas only into the low side until high side shows 250 psi. For at least an instant. If the can gets frost on the outside while charging, warm it some. You dont have to add more and have it stay at 250. As long at it reached 250 for a few seconds then its charged enough. Close can feed, then slowly turn high side connection valve off at vehicle connection, but leave the hoses connected. Then slowly drain the refrigeranent and oil that has accumulated in the lines and gauges into the low side. Let it run a while so the low side sucks refrigerant from any oil still in the hoses and gsuges. Then close the low side valve at the vehicle connection. Wearing safety glasses disconnect both hoses from the vehicle.
After both hoses are disconncted from the vehicle, depressurize the hoses and gauges but expect some oil from the hoses and some refrigerant, so still be wearing safety glasses and dont let oil get on anything you dont want oil on. Connect vehicle side of hoses to storage connections on gauge set.
Good to go.
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^ those pressures are for 134A
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I bought a small indoor / outdoor thermometer and double sided tape mounted it on my center concel with the wire for the out sensor leading into an air duct and the temp. probe mounted with double sided tape inside that air duct. The double display shows the temperature insidecthe vehicle and the temperature of air coming out that air duct both in degree F. When I get in the vehicle and it has been sitting in the sun, the inside temperature can be as high as 132 to 142, and above 112 is common. When running the AC the out temp. quickly falls to the 70's when the vehicle is moving. With the vehicle moving at least 25 mph and recirculate on, if I ocasionally see a Delta of 60 or > between those two temperatures being displayed, when the interiour is > 120 then I know the AC is working good.
As the inside of the vehicle cools below 120 then the Delta becomes even less. And when the out temp. Gets below 49 it slows down in how low it can become with 47 usually the lowest it will sometimes show. On rare times when humidity is very low then the out will show 46 to 44, but below 46 is very seldom. Again, evaporator is limited to 32 because of frosting up, and with a lot of heat transfer and a lot of air moving through, a evaporator to air Delta of 15 is doing good.
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I bought a small indoor / outdoor thermometer and double sided tape mounted it on my center concel with the wire for the out sensor leading into an air duct and the temp. probe mounted with double sided tape inside that air duct. The double display shows the temperature insidecthe vehicle and the temperature of air coming out that air duct both in degree F. When I get in the vehicle and it has been sitting in the sun, the inside temperature can be as high as 132 to 142, and above 112 is common. When running the AC the out temp. quickly falls to the 70's when the vehicle is moving. With the vehicle moving at least 25 mph and recirculate on, if I ocasionally see a Delta of 60 or > between those two temperatures being displayed, when the interiour is > 120 then I know the AC is working good.
As the inside of the vehicle cools below 120 then the Delta becomes even less. And when the out temp. Gets below 49 it slows down in how low it can become with 47 usually the lowest it will sometimes show. On rare times when humidity is very low then the out will show 46 to 44, but below 46 is very seldom. Again, evaporator is limited to 32 because of frosting up, and with a lot of heat transfer and a lot of air moving through, a evaporator to air Delta of 15 is doing good.
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I wanted to retouch on this from since I'm not sure how much it should drop. The high side dropped about 25 PSI within a few seconds of spraying the condenser at about 76 deg ambient.
I also noticed the low side Schrader valve was oozing dye and freon when I removed the line...and lasted about 5 min until it stopped. Wasn't spraying out forcefully but it was bubbling...maybe 2-3 bubbles per second. I don't know how long that can go on like that and really lower the pressure of the system enough to cause issues but since there isn't really too much volume in the entire system I assume not long.
^ ya gotta fix that, but the good news is if it's a typical Shrader core there are tools that will let you change it without losing the refrigerant charge.
It appears to be the typical Schrader, I didn't know there was such a tool, good to know as I will order one. Are these Schrader valves special to 134A. meaning the sealing media? I'm sure an auto parts place has them if so.
You need to get a Schrader valve suitable for automotive A/C, HVAC, or refrigeration systems which typically have Teflon seals instead of neoprene Schrader valves used for tires. More importantly, there are ~5 different sizes/styles of Schrader valves used for automotive A/C systems (with 2-3 being prevalent for R-134a automotive systems).
Be aware that the special valve replacement tools are not inexpensive. Here is a knock-off version that I own: Lichamp Schrader Tool. The name brand versions (e.g., Mastercool, Yellowjacket) are ~$100.
Here is a cheaper work-around solution for bad A/C Schrader valves. If you install this brass plug with Teflon tape, the refrigerant will not escape even if the valve has been compromised. The normal plastic cap with the rubber o-ring is merely a dust cap. I have successfully used the Dorman brass plug on a few vehicles with defective Schrader valves or corroded service ports. They are also available from O'Reilly auto part stores.
Yeah if it only dropped 25psi then it sounds like your condenser is fairly clean. You will need to fix the leaking shrader valve as others have mentioned. This might be all that's wrong with it, it keeps leaking the charge out. Those caps are just dust caps and provide no sealing whatsoever.
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The dust caps do have a gasket, and with a little blue nylog I have gotten them to seal pretty good. I like the idea of a brass plug much better though.
I personally would be looking towards an expansion valve issue or cooling fan issue. You have to do all your testing when the system is giving issues. How I like to check them is when the A/C is malfunctioning trying rapping on it with the back of a screwdriver, pliers, hammer handle, etc and/or take a butane torch to it, the top disk part if possible and heat it for maybe 5-10 second and see what your pressures are like and cooling when it stabilizes. of your pressure look better and/or it starts cooling well then you have an expansion valve issue. For the cooling fan side, do the above mentioned tests while the a/c is malfunctioning and see what happens.
If you can rent or borrow a scan tool capable of reading live data for the A/C then watch the computer's pressure in comparison to the gauge. The pressure sensor could also be messed up and getting skewed to a lower pressure than it actually is which would be commanding the fans on a slower speed than they should be.
Fix your leak but a leak will provide low pressures not high
If you can rent or borrow a scan tool capable of reading live data for the A/C then watch the computer's pressure in comparison to the gauge. The pressure sensor could also be messed up and getting skewed to a lower pressure than it actually is which would be commanding the fans on a slower speed than they should be.
Fix your leak but a leak will provide low pressures not high
