AC questions
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5th Wheeling
Joined: Dec 2024
Posts: 34
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AC questions
Hello. Just trying to optimize my AC since it’s getting hot outside. Overall the system seems to be working well for being a 30 year old truck.
I intermittently get some warm air so I’m hunting down the cause.
I’ve noticed the clutch and compressor are engaged at idle and seems to be blowing cold. According to my AC gauge the low side is about 45psi.
As I increase RPMs, the pressure drops to about 20, the clutch discharges for about 10 seconds as pressure rebuilds, then engages again and holds around 45psi.
Is this normal or does it seem low on Freon? I’ve read both online saying it should hold steady both at idle and with increased RPM
I intermittently get some warm air so I’m hunting down the cause.
I’ve noticed the clutch and compressor are engaged at idle and seems to be blowing cold. According to my AC gauge the low side is about 45psi.
As I increase RPMs, the pressure drops to about 20, the clutch discharges for about 10 seconds as pressure rebuilds, then engages again and holds around 45psi.
Is this normal or does it seem low on Freon? I’ve read both online saying it should hold steady both at idle and with increased RPM
Hotshot
Joined: Jun 2015
Posts: 12,791
Likes: 2,426
It seems to be low on refrigerant. It would only be low on “Freon” if it is charged with R-12. What is the outside air temperature?
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5th Wheeling
Joined: Dec 2024
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According to my gauge it’s in the “green” at idle. Should I charge it past that or to the point where it is maintained across varying RPM?
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5th Wheeling
Joined: Dec 2024
Posts: 34
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95 F350. R-134a
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5th Wheeling
Joined: Dec 2024
Posts: 34
Likes: 9
I did my best to record it. At idle it’s steady between 45-50.
When I hold it at 1,500 RPM, it begins to drop, the clutch disengages, pressure goes up, clutch reengages, and does it over again.
When I let off the throttle, it normalized to 45-50 again.
It does seem to be intermittent. I caught it cycling the clutch on and off at idle earlier today too.
When I hold it at 1,500 RPM, it begins to drop, the clutch disengages, pressure goes up, clutch reengages, and does it over again.
When I let off the throttle, it normalized to 45-50 again.
It does seem to be intermittent. I caught it cycling the clutch on and off at idle earlier today too.
Hotshot
Joined: Jul 2020
Posts: 10,359
Likes: 2,595
From: Near Salt Lake City
40-45 is too high for the low side
Pressure should be 30-35 on the low side
Air in the system will make the low side read high and the system not cool well
I would evacuate it and re charge it with the absolute correct amount of R134a
Pressure should be 30-35 on the low side
Air in the system will make the low side read high and the system not cool well
I would evacuate it and re charge it with the absolute correct amount of R134a
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Hotshot
Joined: Jun 2015
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and 20 is too low which is why the switch is turning off the compressor. That is why I asked for the high side reading. I also would not trust the cheap gauge that comes with the can.
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5th Wheeling
Joined: Dec 2024
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that’s interesting. According to the charts online 45-55 is where it should be for the ambient temp outside
Cargo Master
Joined: Mar 2007
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The low side pressure will determine how cold it will be. If you had a 30psi, the system could freeze up. Basically, the pressure you have will be the temperature you will get out of the vents. Yeah, there are a lot of other things that are involved but it's a good ball park.
Basically, the A/C system take the heat out of the cab and brings it to the front of the radiator. If there is not a good airflow past the condenser, you will not be able to remove this heat efficiently.
Basically, the A/C system take the heat out of the cab and brings it to the front of the radiator. If there is not a good airflow past the condenser, you will not be able to remove this heat efficiently.
Laughing Gas
Joined: Oct 2014
Posts: 946
Likes: 186
From: Carnation, Wah
Without a high side pressure, you're just guessing-
but my guess, too, would be that you are low on refrigerant.
Easy enough to add 3 oz, and see if the behavior changes.
The charts that I use also take humidity into consideration.
t
not an a/c expert
but my guess, too, would be that you are low on refrigerant.
Easy enough to add 3 oz, and see if the behavior changes.
The charts that I use also take humidity into consideration.
t
not an a/c expert
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