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Old 03-09-2012, 05:58 PM   #1
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Charged up the chassis AC, it works

Does anyone know what the hi and low side pressures should be on the ford 460 motor ac.
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Old 03-09-2012, 06:37 PM   #2
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r-12a or r134
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Old 03-09-2012, 08:35 PM   #3
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Originally Posted by Bilito View Post
Does anyone know what the hi and low side pressures should be on the ford 460 motor ac.

A good rule of thumb, and the method I used mostly when I did that type of work was;
High side should be about 2.2 to 2.5 times the ambient outside temperature measured about 6 inches in front of the condenser.

i.e. 75 degrees 2.2 X 75 = 165 p.s.i

If the system is working properly, the low side should take care of itself.
For giggles though... 50 psi or less on the low side after the system has equalized. That number will come down as the inside temperature goes down.
Anyway, if you charge by the high side using the ambient temp, that should be close enough to keep you cool for the summer.

Good luck!
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Old 03-09-2012, 10:20 PM   #4
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You really need to consult a refrigerant pressure temperature chart for therefrigerant in you system. Evaptemp...about 40 to 45 dF, condenser, use the pressure for about 20 dF over the ambient temperature. If this does not make sense, you need to hire a technician.

Ken
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Old 03-10-2012, 08:06 PM   #5
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Originally Posted by Phobos View Post
A good rule of thumb, and the method I used mostly when I did that type of work was;
High side should be about 2.2 to 2.5 times the ambient outside temperature measured about 6 inches in front of the condenser.

i.e. 75 degrees 2.2 X 75 = 165 p.s.i

If the system is working properly, the low side should take care of itself.
For giggles though... 50 psi or less on the low side after the system has equalized. That number will come down as the inside temperature goes down.
Anyway, if you charge by the high side using the ambient temp, that should be close enough to keep you cool for the summer.

Good luck!
It was in the hi 70's perhaps the low 80's yesterday, the system was sitting idle and dead for 4-5 years, but it did have some pressure in it 5 -10 psi. I got a Kit that had the new fittings for R134a and 3 cans of freon with oil and sealer in it. The oil is supposed to mix with the old R-12 oil. I got in almost 2 cans when the compressor kicked on. The pressure was 25 low and 150 hi and the air was pretty cold. Added some more freon from the 3rd can and got the presure to 30 low and still 150 hi and decided to call it day when the supper bell rang.
Have not had a chance to do anything today but run errands. I guess it would have been a good idea to change the dryer and expansion valve but I hate to open it up since I do not have a suction pump. Don't know if it leaks or not, will have to wait and see. Waddayathink guys????
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Old 03-10-2012, 08:19 PM   #6
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You can make a suction pump out of an old refrigerator compressor. Adapt some fittings to match your gauges set. It will pull it down to almost 30".
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Old 03-10-2012, 08:28 PM   #7
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Since the system did have some positive pressure in it, it probably does not have moisture in it - that's good news. It's when the pressure goes to zero that moisture can migrate into the system.

You should have a capacity label somewhere near the A/C service ports. If the original freon was R-12, the rule of thumb is to decrease the capacity (number of ounces) by 10% when converting to R-134A.
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Old 03-10-2012, 10:05 PM   #8
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Originally Posted by Bilito View Post
It was in the hi 70's perhaps the low 80's yesterday, the system was sitting idle and dead for 4-5 years, but it did have some pressure in it 5 -10 psi. I got a Kit that had the new fittings for R134a and 3 cans of freon with oil and sealer in it. The oil is supposed to mix with the old R-12 oil. I got in almost 2 cans when the compressor kicked on. The pressure was 25 low and 150 hi and the air was pretty cold. Added some more freon from the 3rd can and got the presure to 30 low and still 150 hi and decided to call it day when the supper bell rang.
Have not had a chance to do anything today but run errands. I guess it would have been a good idea to change the dryer and expansion valve but I hate to open it up since I do not have a suction pump. Don't know if it leaks or not, will have to wait and see. Waddayathink guys????
As a general rule, refrigerants should never be mixed in a system, but since the dead is done, let's move on.

If it's cooling the interior down in 80 degree weather, I'd say you're close enough without accurate temperature readings.
Be careful, if you overcharge the system, you can lock the compressor and damage or destroy it.
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Old 03-11-2012, 07:25 PM   #9
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It is putting out some fairly cold air, I have to figure out why 90% of the air is going to the defroster, gotta be a stuck valve or a disconnected vac line somewhere.

As far as worrying about the pressures I am going to let that take back seat for now as long as it is making cold air. I am now moving on to my next issue in a new post.
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Old 03-14-2012, 09:19 PM   #10
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I vote vac line or vac check valve
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Old 03-15-2012, 01:48 AM   #11
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Can't remember if the Fords use the vac controls for the dash controls or not. If your has the vac controls on the dash these can leak also.
I have found many pencils, bobby pins, etc. holding the heater/ac doors open.
Try sealing off the defrost vents and see if it comes out the dash vents.
I put about the same amount of HFC134a in my '88 Itasca with 454 as you did with your rig. Only difference was mine has all new lines, expansion valve, drier, o-rings, oil, and rad. fans come on with the a/c.
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Old 03-15-2012, 06:52 PM   #12
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Can't remember if the Fords use the vac controls for the dash controls or not. If your has the vac controls on the dash these can leak also.
I have found many pencils, bobby pins, etc. holding the heater/ac doors open.
Try sealing off the defrost vents and see if it comes out the dash vents.
I put about the same amount of HFC134a in my '88 Itasca with 454 as you did with your rig. Only difference was mine has all new lines, expansion valve, drier, o-rings, oil, and rad. fans come on with the a/c.
This has a vac system, or at least I am pretty sure it does. I have a small round black plastic ball about 6 inch in diameter with a small hose line going to it and the other hose line attach point has no hose and no vacuum, I guess that ball is a vac chamber to maintain a steady vacuum, in my youth we made a vac chamber from an old soup can to keep the wipers running when we stepped on the gas or went up a hill

I did find a vac port on the intake manifold with about four or five vac lines leading out of it and one was missing a line so I plugged that with a small piece of hose with a plug in it and the engine suddenly ran real smooth, I also found a loose vac iine hose in front of the radiator, I have no idea where it comes from or where it goes but it has no suction, there is a vacuum valve deal with a hose dangling from it on the box the ac evaporator is in with the heater coil. I can suck on the line and hear a valve close in that box

sticking out of that box at the side near the top is two pipes that I guess were for the heater and near it is the heater hoses with a 180 bend and connected together. I can assume from that that the heater coil probably either leaks or makes a lot of heat here in florida

Not sure where to start, would be nice if I had a vaccum diagram for the heater and ac, but also there is those two air pumps for the environmental system that are not connected, I think there might be some vac lines associated with that.
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