AC thread - orifice tubes

[david85]

Today it got bloody hot and my truck doesn't seem to do as good as I thought. If I'm driving the AC works well, but idling, was not so great. As it turns out my AC vent was 25% clogged with maple blossms from spring and the leaks in the air ducting didn't help either, but I'm still thinking of some longer term upgrades for the system even if not this year.

A few questions about orifice tubes.

What is the difference between red and blue (currently running a blue orifice with duracool hydrocarbon refrigerant)

Does anyone have a before and after perfromance result for swapping to a vafiable orifice tube? is this something that ford normally carries?

 

[f-two-fiddy]

Go with a variable orifice tube

A quick search will give up the info

 

[Dirtleg]

X2 on the variable orifice tube. My system was originally r12 now it's 134a. You'd never think it wasn't designed for 134a as it will freeze you out of the truck.

 

[david85]

Is a variable orifice tube likely to be available at a regular parts store?

So whats the difference between red and blue tubes?

 

[NJKen]

Variable orifice tubes are available at most auto parts stores. I know you can order them from NAPA and most online parts places.
The blue orifice tube has a bigger orifice than the red one. the natural colored one (or white) is the biggest of them all. If you only have a standard cab pickup truck you could use the red one if you would like. By slowing the flow a little bit the freon has a little more time in the condensor to shed some heat. Most problems with poor cooling at slower speeds are related to non condensables. That means that there may be air in the system or even too much oil. Before you charge it you should pull a good vacuum on it for at least an hour.
Ken

 

[david85]

I suspect I did have too much oil and I pulled the compressor yesterday to drain some out. Seems to be doing better now. I sacrificed some refrigerant from the rest of the system to purge the air out of the comressor the best I could but there could still be some air left in there. I will certainly pull a good vacuum when it comes time to swap orifice tubes.

Turns out Duracool comes precharged with oil right in the can....

If I follow you, you are telling me that larger orifice tubes result in more cooling capacity?

 

[sle2115]

If I follow you, you are telling me that larger orifice tubes result in more cooling capacity?

The larger orifice tube allows for faster movement of the refrigerant, that might be a good thing or bad. It needs to be in the evaporator long enough to cool it, but move on before it starts warming so more "cold" refrigerant can move in and keep it cold.

 

[typ4]

Go with the variable, it is a great problem solver. Also the oil in can is a good way to screw up the system, as you just found out. It may be time to do a flush and replace the refrigerant and a new drier.

 

[david85]

*sigh* what exactly is the drier and why should I replace it?

Is that the round can next to the evaporator that gets cold?

I tried it again today just idling it and its not too bad, but I wouldn't consider it "cold". If I bump the idle up to 1000 RPM from the normal 600, it does start getting cold.

 

[NJKen]

If you dont have a big passenger compartment to try to cool you do not need a big orifice. The blue one should do fine. I am not totaly up to speed on the refrgierant that you are using but if you go to aircondition.com there is an excelent alternative refrgierant forum there. If you have a suspect oil overcharge you will need to blow out the system real good. You should change the accumulator (yes its the round thing next to the evap) because it has a desicant bag in it. That is there to remove any stray moisture. Chances are that yours is saturated. They can be found cheap enough if you shop around a little.
The key to your problem is getting the oil charge rite and getting the system evacuated really good. Even if you stick with the blue tube you should be fine. I persoanlly would not put the red tube in there because the FS6 compressor can really move some freon. Making the orifice too small will cause very high pressure and temperature in the condensor that will only cause undue wear and tear on the parts.
If you just take care of those basic items your AC should blow snow at you
Ken

 

[david85]

So thats what that round thing is. Now I know why everyone says to replace it

Why do I get the feeling that alone could be my problem? Oil overcharge doesn't help though. I know the AC system in my truck had been messed with by the PO so who knows what is in it. I cleaned everything out with solvent when I overhauled the system a couple of years ago, but it sounds like the dryer isn't something that can be cleaned.

Incidentally, I don't have an FS6 compressor, but instead its a later R134a compressor of some sort because the old one burned out. I modified it to fit because it was so cheap second hand. It seems to be a later version rotary compressor and is about the size of the older FS6.

 

[cm1hedge]

If you ran solvent through the accumulator, it is toast. Replace it.

 

[RLDSL]

The variable orifice valve is part # 1502002 , or it is sold under a number of other names 38902 would be the Four seasons/ true mark/ factory Air part number for the one that would be best in your climate ( i.e. below 105 deg ) Car Care Corp sells it under the name Self adjusting orifice valve AC38904 should be the number there. The NApa # is 207325

Those things do wonders, I put them in ever system I open up. An electric pusher fan in front of the condenser will help a bunch in traffic. Your engine fan doesnt kick on enough to draw enough air through at low speed to help the ac. Insulating the evaporator box in the engine compartment helps a whole lot as well. also doing the hot water valve bypass that is mentioned in the stickys is a big plus

 

[david85]

If you ran solvent through the accumulator, it is toast. Replace it.

Doing some more reading on them and it seems that it can also clog with crap from a blown compressor. Maybe this overhaul should not wait for next year.......

You've all been a great help guys. Big thanks!

 

[david85]

Go with the variable, it is a great problem solver. Also the oil in can is a good way to screw up the system, as you just found out. It may be time to do a flush and replace the refrigerant and a new drier.

Is there any way to know how much oil to add if there is already oil in the refrigerant? Could it be that I shouldn't add any at all in this case?