AC Orifice Tube

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Originally Posted by Helirich

I used my robinair reclaim machine. I don't recall any perticular freon. It seemed to work. Did I screw it up for later?

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For the unit, you'd have to look at its manual. Some have oil-less compressors and made to recover several types of refrigerant, liquid/gas, etc. Mine is what they called a "station". It's older than dirt and I don't think it would like 134a because it has mineral oil.
I don't think one time would ruin it, but you might have mixed refrigerants...depending on what, if anything, was already in it.

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Originally Posted by Ron

For the unit, you'd have to look at its manual. Some have oil-less compressors and made to recover several types of refrigerant, liquid/gas, etc. Mine is what they called a "station". It's older than dirt and I don't think it would like 134a because it has mineral oil.
I don't think one time would ruin it, but you might have mixed refrigerants...depending on what, if anything, was already in it.

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My reclaim machine doesn't hold anything. It just pumps the freon out of the system into a tank. The tank I had previously vacuumed out, so there should be no mixing.

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Originally Posted by Helirich

My reclaim machine doesn't hold anything. It just pumps the freon out of the system into a tank. The tank I had previously vacuumed out, so there should be no mixing.

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Ah!...you don't know what the PO had in it???

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Originally Posted by Ron

Ah...you don't know what the PO had in it???

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Not following you. If you mean the tank, I bought it new and used it once to hold R22. That was put back in the fridge and whatever was left should be gone when I vacuum it out.

If you mean the system, it should be R12, but I guess the PO could have mixed it. If it was converted, they should have changed the fittings.

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Originally Posted by David T

Unless you have to remove the orifice tube, either because it is broken or plugged up, leave it alone. It is in a place where the pipe is bent and it can be difficult to remove without damaging that VERY thin aluminum pipe. Once you damage that pipe you are replacing the evaporator coil and it is NOT a fun job. I do not understand why some people feel they have to "convert". R-12 is readily available, it is not that expensive, and you don't need much.

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We ought to call it the Pipe Of Regret.

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Originally Posted by Helirich

Not following you. If you mean the tank, I bought it new and used it once to hold R22. That was put back in the fridge and whatever was left should be gone when I vacuum it out.

If you mean the system, it should be R12, but I guess the PO could have mixed it. If it was converted, they should have changed the fittings.

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??? I must have misunderstood what you were asking here:

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Originally Posted by Helirich

...Did I screw it up for later?

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Originally Posted by David T

Unless you have to remove the orifice tube, either because it is broken or plugged up, leave it alone. It is in a place where the pipe is bent and it can be difficult to remove without damaging that VERY thin aluminum pipe. Once you damage that pipe you are replacing the evaporator coil and it is NOT a fun job. I do not understand why some people feel they have to "convert". R-12 is readily available, it is not that expensive, and you don't need much.

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On my Bronco, the orface had a bunch of junk on it. This was on a working AC. I only pulled it because it was easy and I had the system down for a condenser replacement. I haven't even looked at the orface location on the D yet. I guess it's no fun.

I have experimented with the GM white orifice tube, the variable orifice tube, the Ford blue orifice tube, as well as the Ford Red. Blue is smaller than white, red is smaller than blue. I have noticed better performance with the blue over the white for sure. The red is installed now and I'll be charging my system the next month or so. I've used the variable tubes but not been a fan; personally I haven't seen the improvement with them. I know others have had different experiences thought with these.

Orifice diameters are as follows:
GM White .072
Ford Blue .067
Ford Red .062

With the orifice tubes, the smaller the orifice, the slower the release of refrigerant causing lower pressures on the low pressure side. The lower the pressure and more opportunity to expand, the colder the refrigerant will get. There is of course a point of diminishing returns where you either simply cant get enough refrigerant flowing, or, you allow it to continue to expand so much that you freeze up. There's no question in my mind though that the Ford blue performs better than the GM white. Search any 80's corvette site (DMC used the same accumulators, low pressure switches, orifice tubes, and functioned the same way cycling on and off) and you'll find countless threads on this topic. I'm still unsure where I'll land between red and blue. Ford orange, green, and brown get even smaller (down to .47) but I suspect that's far beyond the point of continued returns. I've rarely read of anyone using smaller than red.

Thanks!, Nick.

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Originally Posted by Nicholas R

I have experimented with the GM white orifice tube, the variable orifice tube, the Ford blue orifice tube, as well as the Ford Red. Blue is smaller than white, red is smaller than blue. I have noticed better performance with the blue over the white for sure. The red is installed now and I'll be charging my system the next month or so. I've used the variable tubes but not been a fan; personally I haven't seen the improvement with them. I know others have had different experiences thought with these.

Orifice diameters are as follows:
GM White .072
Ford Blue .067
Ford Red .062

With the orifice tubes, the smaller the orifice, the slower the release of refrigerant causing lower pressures on the low pressure side. The lower the pressure and more opportunity to expand, the colder the refrigerant will get. There is of course a point of diminishing returns where you either simply cant get enough refrigerant flowing, or, you allow it to continue to expand so much that you freeze up. There's no question in my mind though that the Ford blue performs better than the GM white. Search any 80's corvette site (DMC used the same accumulators, low pressure switches, orifice tubes, and functioned the same way cycling on and off) and you'll find countless threads on this topic. I'm still unsure where I'll land between red and blue. Ford orange, green, and brown get even smaller (down to .47) but I suspect that's far beyond the point of continued returns. I've rarely read of anyone using smaller than red.

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Exactly what I read with the corvette guys. They have almost the same system as we do.


Let us know how the .062 Red OT works. I’m going to first use the .067 Blue, but if you have better luck with the red then I’ll go with that.