Hi Guys,Now that we have that all straightened out.I will insist for an overnight vacuum pull down to minimize any moisture.My receiver/dryer is newly rebuilt by Classic Air.I have been told that we need to put another expansion valve and that my symptoms can be caused by a bad unit.Ray just stated:"This is the cold LOW pressure liquid, going thru the expansion valve where it starts to become a gas again. This valve mostly regulates the amount of flow which regulates temps. It actually allows passage at a given temp and STOPS it at a lower temp.First: I get great cooling inside the cabin from a cold start.The line that empties the evaporator, after it is fed thru the expansion valve and the evaporator, is cold as is the filter bulb that feeds the condensor. This line becomes hot and the cooling stops after 10 minutes.Second: I get great cooling at highway speeds, pull off to check the temperatures and the cooling stops and never returns even after shutting off the A/C for 10-15 minutes and turning it back on.Compressor is engaged. There is no visible frost.Compressor is controlled by a temperature controlled switch that shuts the compressor off if evaporator coil freezes.Soon, if everything works extremely well then it craps out without any visible freezing.Does anyone think that we are on the right track and it sounds like a bad expansion valve?Also, it works better with 4 lbs. of 134A than with the recommended 2.5 lbs. which is 70-80% of normal? 3 lbs.Does that reinforce a bad expansion valve.Thanks,TonyPS I heard that you guys have enough R-12 to carry you thru until Y3K. 😎
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I hate to say it Keith, but you got some wrong too. The compressor takes the low pressure gas from the evaporator and turns it into a high pressure gas. The compressor cannot compress liquid any more than an engine can. The high pressure gas “condenses” in the condenser and becomes the high pressure liquid. When it hits the expansion valve, it goes to a low pressure, low temp liquid and is evaporated into a low pressure gas by the air flow over the evaporator. It then goes back to the compressor and the cycle starts all over. High side is hot, and low side is cold. Any cold on the high side means a restriction.Don, with an equally cold 66 Imperial.
Hate to say it Ray, but you got most of that A/C info backwards. You might want to check out a tutorial like this one:The compressor actually turns the gas into a pressurized hot liquid. The liquid goes through the condenser coils up by the radiator where it partially cools off. This is normally referred to as the "high side". Then it flows to the expansion valve just before the evaporator coils. The high pressure of that liquid is released at the expansion valve, turning it to a very cold gas there and becoming the "low side". This makes the coils cold and they absorb heat from the air passing through them. The low-side gas, which is still quite cold, then returns from the evaporator to the compressor to be compressed in to liquid state again.One part you did get right is the critical importance of system evacuation before charging with freon. Because low pressure cause liquids to turn to gas, when you vacuum the system for several hours it causes the contaminating liquids, including water and oils, to boil into a gaseous state and be drawn out by the vacuum pump, and thereby cleansing the system before freon charging.And one final tip: If you can't or don't want to buy a new receiver/drier (which is your A/C system's garbage can) it is possible to "rejuvenate" your old one. Use an old toaster oven - which you probably keep around anyway to bake paint on small parts. Take it out into the garage or outdoors and bake the receiver/drier in it at 400 degrees for a couple of hours. It may stink to the high heavens, but that process will boil out whatever garbage is in there - same as turning on your self-cleaning oven. Give it a new coat of paint, bake it again at 250 for 15 minutes, and it will look and perform like a brand new champ again.Keith BoonstraFreezin' a can of beer in front of my '57 A/COn Sat, Jul 9, 2016 at 1:30 PM, Ray Jones 1970hurst@xxxxxxxxx [Chrysler300] <Chrysler300-noreply@xxxxxxxxxxxxxxx> wrote:
Tony;The problem with replacing the Expansion Valve is that you probably are not curing a problem.The Compressor squeezes the liquid into a gas, making it very cold.That's why the line from the Compressor is cold and usually sweating.The Expansion Valve's job is to reduce the gas to a liquid, via a small orifice.As the liquid goes thru the evaporator, it absorbs heat and turns back into a gas,then to the Condenser, where it sheds a lot of the heat, back to the Compressor, and so on.That's why going into the Evaporator the line is cold and coming out it is hot.If there is moisture in the system it will form a ice ball in the orifice and block the system.Later it will melt and operate for a while, until it clogs again.Key here is proper evacuation. Even that is problematical if the Receiver-dryer is loaded with moisture, it's job.If you haven't replaced the Receiver-dryer, do it while you have the system down this time.There could be blockage or excessive moisture there.Be sure to add any needed A/C oil, the new Receiver-dryer will require some.You also mentioned blowing out the Evaporator, high pressure air going into here is a bad thing.Air/moisture can be in lots of places inside here and not be removed with a light Evacuation.I would suggest you have it Evacuated for at least several hours to be sure it is fully purged.You want near 25" of vacuum, won't get there, but closer the better.Then let it sit overnight and see what the Vacuum is in the morning, before charging.Extra work, but with the constant problem you have, might as well overdo and be sure.God luck, Rayp.s.: we're sending our heat wave to you, enjoy...On Sat, Jul 9, 2016 at 8:00 AM, Tony Rinaldi awrdoc@xxxxxxxxx [Chrysler300] <Chrysler300-noreply@xxxxxxxxxxxxxxx> wrote:
My system is a 1962 installed into my 1960 300-F.A mechanic tried to convert to 134A without taking the EPR valve out of the compressor. It worked great but would freeze up the evaporator and stop working.Sent everything to Classic Air for rebuild and conversion. Their temperature switch makes and breaks power to the compressor blue wire if there is a freeze up. This replaces the function of the EPR pressure valve to cycle the compressor.The evaporator is open and was blown out with compressed air.System was charged and was not cold.Classic Air said it was a bad expansion valve. Replaced it and no difference.They said to charge the system with 134A at 80% of normal pressure. So they went down to 2.5 from 3 lbs.Problem is that the filter housing on the top of the condenser gets cold but the line does not get cold where it enters the evaporator.They put 4 lbs. in and I got 59 ° at the vents on the highway.Pull off to the side of the road, with engine running, to see it working well and the cooling stops. Nothing frosting up.Go back on the road and the cooling does not come back.Waiting for another expansion valve and on/off switch to be delivered.Will be replacing both once they come in.Any insight about where we are now?Thank you, in advance, for any help or suggestions.Tony
Ray Jones. Y'all come on down an see us. Ya hear?
--Ray Jones. Y'all come on down an see us. Ya hear?