Air Conditioning gods needed.

[PackRat239]

Sinc my first answer did not go thru, here it is again. The basic refer system works this way. First, it does NOT make cold, it absorbs the heat out of the air and puts it outside. As the compressed refrigerant expands into the evap unit, the fan blows air across the evap, and it absorbs the heat out of the air as it crosses the fins, giving you nice cool air. The refrigerant with the heat then travels to the condenser core, where your engine fan and airflow remove the heat from the system. And so on ... etc... Hope you can make some sense from my ramblings...

So what exactly causes an ac system to not cool properly. I am stil trying to uunderstand how and ac system works.
What I think I know is when there is a pressure drop with the freon it cause the temperature to drop.[/QUOTE]

 

[cowman79]

I knew that a person with AC experience would correct me for saying cooling and not heat removal. So is it the pressure drop that give the freon the ability to remove the heat or is it that removing the heat causes the pressure drop.

 

[firehawk]

I knew that a person with AC experience would correct me for saying cooling and not heat removal. So is it the pressure drop that give the freon the ability to remove the heat or is it that removing the heat causes the pressure drop.

That's just silly, just like trying to correct someone when they say dark rather than low light.

For all my a/c work, I shoot for 300 psi high at high rpm. It works great, and all my cars blow cold even on very hot days.

 

[cowman79]

I used to work with an older ac guy and that was one of his sticklers was removing heat not cooling.

 

[PackRat239]

Not pressure drop, but the rapid expansion, kinda like letting the air out of a balloon. The compressor fills the baloon, and then it is released. The same as with nitrous. In the bottle under pressure it is at room temp, but when you release it, the rapid expansion makes it really cold.

 

[dshane]

does it have a expansion valve or oriface tube? after you pull vacuum on it are you purging the line with freon when you change cans
if not your mixing air in( non condensibles )

 

[ifrythings]

check out this link http://www.fordforumsonline.com/forum/attachments/heating-air-conditioning-cooling-systems/537d1273176021-ford-ac-charts-information-ford-ac-system-charts-information.pdf.

it has al the pressure and temperature readings and diagnosis you'll need.

Also, since you have used a stop leak in the system, it has now plugged up your orifice tub and very possible the evaporator and condenser could be partially blocked

 

[chris142]

High side pressures should be close to 2.2x ambient temp and never more than 2.5x ambient with a single system.

And ya stay away from the stop leak crap.

 

[cowman79]

That is great information.

Also I should let everyone know That i drove the truck to work on Friday when it was around 85 degrees and the truck performed flawlessly. I am thinking maybe it was a problem with the air flow across the condenser. I out a new viscous clutch fan on the truck a couple of years ago but it was a cheap one i am guessing it may not be working properly.

 

[RLDSL]

That is great information.

Also I should let everyone know That i drove the truck to work on Friday when it was around 85 degrees and the truck performed flawlessly. I am thinking maybe it was a problem with the air flow across the condenser. I out a new viscous clutch fan on the truck a couple of years ago but it was a cheap one i am guessing it may not be working properly.

Always charge with a big box fan blowing across the condensor to imitate road speed, especially with clutch fan systems, now adding oil, if you didnt see signs of oil leakage around any joints will have effectively changed the volume of your system and will throw all pressure readings to the four winds, you now have to just throttle the juice in till it feels right. For the kinds of temps you have been having outside, 45 on the low is a near empty system if you were charging mid day, screw the charts, I think those things were all written by someone in Manatoba. You should bee seeing around 65 of so on the low side mid day ( this will change drastically at night , but do not expect the system to cycle during the heat of the day). and look in the archives for the heater valve bypass, if you havent done it yet... do it, otherwise you have hot water flowing through the dash at all times, this will shut it off while ht eac is on high.

Lastly, these trucks, the fittings ford used, are notorious for leaking when r134a adapters are left in place, so once you install the refrigerant and get it all set, REMOVE the adapters and tag your lines that the system containes R134a and cap off the old R12 fitting( you will likely need new valves if an adapter has been in place before they squash the r12 valve and jam it open in some cases) if you were smart and got some nylog for orings, put a little around the valve seals. On most that I have run across where they have been converted and they leak, the sniffer doesnt lie, the valve adapters have been the culpret in most cases. And do make sure to run the vacuum for a good long time like overnight if the system has been out of use for an extended period, you are not just removing air, you are boiling and removing water at ambient temperature with the vacuum pump, if you dont get it out, you will have evaporator icing.

 

[firehawk]

Whenever I convert an r12 system, I always use the fittings that have their own valve stem and remove the r12 ones. The ones that push down on the r12 stems have problems.

 

[cowman79]

My truck originally had 134a in it but I just replaced both the high and low side fittings with new ones. I replaced them with the same style they were both the ball style not the schrader valve style. I used to use one of the can style hoses that had a green line all the way up to 65 psi which is where I usually fill them up to but this time I didn't because I was concerned it was over charged and not cooling properly. I was using and actual set of gauges that doesn't tell you where to charge it to you are supposed to know.

 

[RLDSL]

My truck originally had 134a in it but I just replaced both the high and low side fittings with new ones. I replaced them with the same style they were both the ball style not the schrader valve style. I used to use one of the can style hoses that had a green line all the way up to 65 psi which is where I usually fill them up to but this time I didn't because I was concerned it was over charged and not cooling properly. I was using and actual set of gauges that doesn't tell you where to charge it to you are supposed to know.

Chances are without extra air blowing across the condensor, it wouldnt matter how much you tried to squeeze in there ( and youd have a heck of a time doing it without the extra air flow as your pressures would be fighting you the whole way, it wouldnt get cold enough. It could be reading 65+ and you put a fan on there and it'll drop to 35, which is way too low for a hot outside temp, meaning you would be under charged, which is why you need to charge with the extra air flow. .
With the ac on high windows up you should be able to get some seriously cold duct temps, in the evening they should approach 35-37 deg with a standard orifice tube which is dang cold for a small cab if you get mid 40s or so in teh day you are doing great
You can test at night when its cool out for proper cycling by running it on high for about 20 minutes , and turning the inside blower down to 1 and read teh duct temp and watch teh pressure on teh low side, temps should approach freezing , without freezing and the compressor should cycle off before duct temps reach freezing, if it drops below freezing, you have a screw on teh accumulator switch you can adjust to have it cut the compressor out at a higher pressure so you dont ice the evaporator

 

[cowman79]

I am guessing now I will be doing some more testing and adding a little more freon. I will probably run the sniffer over it first to make sure my valves are not leaking anymore before I top the system off.