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K. Wiggins
K. Wiggins, ASE Certified Technician
Category: Chevy
Satisfied Customers: 2992
Experience:  ASE Certified Technician, Associates Degree in Automotive Technology, 15+ years in the trade
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This is regarding the 1990 K1500 383 stroker FAST EZ efi 2.0

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This is regarding the 1990 K1500 383 stroker FAST EZ efi 2.0 project. Where/how is the AC orifice tube installed?

The oriface tube is in the high side line at the evaporator core. You have to remove the high side line from the evap core and look into the line of the evap core. It should be right there a the top of the line. When you put the new oriface tube in, the end that has the orings on it goes into the evap core first.

Hello and thanks for requesting me. On this model the orifice tube is NOT located at the evaporator core. It's at the line coming from the condenser.

You'll need to remove the passenger side parking light assembly and grille, then you can access it. A picture here shows which line. Let me know If I can help further.

Customer: replied 1 month ago.
The new condenser came with a new oriface tube. Black end with screen goes into tube correct? How far down the tube should it go before it is in place?

Correct, black end into tube. Put a little pag oil on the oring and slide it in until the end is just below the surface, you'll feel it bottom out on the crimp in the line.

Also make sure to put 2oz of your pag oil into the new condensor. Total system capacity is 6oz. I usually do 2 in condenser, 1 in drier, 1 in evaporator and 2 in compressor

Customer: replied 1 month ago.
Is it directional? Does flat surface of oriface tube align with anything?

No, only orientation that matters is the long part with screen

Customer: replied 1 month ago.
I have a 1990 K1500 Silverado that I have been using as a donor truck for my project truck. My project truck did not come with factor AC, the donor truck did. I removed the entire hvac box, with blower motor, heater core, evaporator core etc, installed it into my project truck. When I went to install a new evaporator core, one of the lines was soldered incorrectly, would not fit like it should have. Before, I took the donor truck apart, I was driving it, and know that the AC worked great, with no issues. I had to get this part of the project completed. Installed the donor vehicle's evaporator core back into place knowing that there were no issues with it. The picture that I sent is of the donor vehicle's condenser. It is built differently than the new one that I am installing and the picture that you sent. Would the donor vehicle's oriface tube be located in the same position in the high side line as the the new one that I am installing? Would it be in the evaporator core that is now installed in my project truck? I don't believe that it is in the evaporator core.

I can't see a crimp in that one, but if you have no orifice in the used evap core and the tube in the new condenser it will work properly. On these it's always going to be in the small diameter line running from condenser to evaporator. The give a way is a crimp or indention in the line a few inches past the fitting.

Customer: replied 1 month ago.
Good call on the crimp. It wasn't in the evaporator core or in that section on line at the condensor. On the donor truck, the high side line that goes from the condenser to the evaporator is 2 piece. There is a crimp in the line near the fittings, about the midpoint if it were a 1 piece line. It was there at the crimp. This will still work correct? The new condensor would have the black end going in first pointing down towards the condensor. The donor truck's oriface is pointing in the opposite direction, with the black end with the screeen pointing towards the evaporator core. Will that matter? I have a new high side line, not sure if it's 1 piece or 2 piece. If it is one piece will I need to use the donor truck's high side line and install the oriface tube in the same location or install the oriface tube in the new condensor as we previously discussed? Can the new oriface tube be installed in the condensor in the direction the we previously discussed and the new line?

The donor truck must of been built before oct 31 of 89, that's when they went to the newer design like the new condensor you bought.

If you have to use the donor trucks line and condenser you'll have to put it in that line. From what I see it doesn't look like the new condenser would work with the donor truck line. (angle of the condenser outlets.

Whenever you replace an orifice tube it always goes long screen side towards the condenser. Under that screen is the orifice that turns the refrigerant from liquid to a gas to enter the evap core.

I hope that makes sense. HERE is a diagram of how the flow works

Customer: replied 1 month ago.
I don't have to use the donor truck's condensor and line. I do need to use the installed evaporator core. Will the evaporator core work with the new condensor if use the new, not the donor truck's line?

Thread wise it should work. May have to need the line some if it's off. I don't think they changed evap design so everything should work with new line and condenser.

K. Wiggins, ASE Certified Technician
Category: Chevy
Satisfied Customers: 2992
Experience: ASE Certified Technician, Associates Degree in Automotive Technology, 15+ years in the trade
K. Wiggins and 2 other Chevy Specialists are ready to help you
Customer: replied 1 month ago.
That it the line with the crimp. The oriface tube points towards the evaporator core. That seems like it would indicate that the flow is reversed. However the evaporator core has a larger diameter tube (for low pressure) on the top, and a smaller diameter tube on the bottom (for high pressure). The orientation of the evaporator core seems correct, like it should flow in the right direction. Why would the AC work if the oriface tube points in the opposite direction?
Customer: replied 1 month ago.
That's the R front tire with the line pointing in the direction that it was removed. The line with the fitting and schrader valve just to the inside of the tire is where they fasten.
Customer: replied 1 month ago.
I just checked the new evaporator core that was built incorrectly. It came with a new oriface tube. That means that the new evaporator core is supposed to have the oriface tube installed into it. The oriface tube would be pointing in the same direction as the donor truck's setup.

OK, so does the new condenser and line work with donor evap?

I'll be back in about 30-45 minutes.

Customer: replied 1 month ago.
I haven't installed the condensor yet, but I am sure that I could get either the new line or the donor truck's line fit. Without the oriface tube, both the new and the donor truck's line should function the same. They are both lines. The engine does not run yet, so there is no way to check if everything works together right now. I do need to get the front of the truck together to get it to the exhaust shop. That's why I need to figure out if the new condensor will work with the evaporator core.
Customer: replied 1 month ago.
I will get the condenser w/o oriface tube, if it is needed to make this work. That is the condenser that is in the donor truck. I could use the donor truck line, if I needed to. I am still concerned that the oriface tube would be installed in the opposite direction of your diagram. I am 100% sure, positive, that the AC in the donor truck worked with the black screen part of the oriface tube pointed towards the evaporator core.

Thanks for your patience. I can confirm the ac will work with the tube either way. I would recommend installing it long end toward condenser for the filter effect of the screen though.

Customer: replied 1 month ago.
I understand the filter screen theory. That does make sense. However, in this situation, do you think it would be best to get a similar condenser w/o oriface tube, like the picture that I sent, because I am using the evaporator core from the donor truck, and that I know that the AC worked great with the oriface tube long end pointed towards the evaporator core. I am basically using the entire AC system from the donor truck. I am not sure if I used the condenser that had the oriface tube with the pointed towards it, that it would work.

Yes, I would go ahead and get the one that matched the other truck. That way you also know the compressor hose assembly will bolt up as well.

Customer: replied 1 month ago.
Are the oriface tubes the same or diffferent depending on what direction that they face? I know that they aren't much, but I think that I am just going to pull out the oriface tube and clean it. Can they be cleaned and reinstalled with a new o-ring? Can they be cleaned with brake parts cleaner?
Customer: replied 1 month ago.
They are different. I will replace it.
Customer: replied 1 month ago.
I would need the evaporator mounting correct?
Customer: replied 1 month ago.
I would need the evaporator mounting correct? Thank you.

Yes, the evap mounting (white one) is the one you want.

Confirmation via GM TSB

PN mentioned here at rock auto. Nothing wrong with RA's house brand wither, I use them often.


Customer: replied 1 month ago.
I just pulled the oriface tube out of the donor truck's line, placed it on the tire. That is the orientation of it in the tube. It is installed with the short end into the tube first. The screen end towards the condenser. I still need the condenser w/o oriface tube, and would need the condenser mounting correct?


Customer: replied 1 month ago.
This is the right direction.

That's definitely how it should be.

Customer: replied 1 month ago.
Do you have the part number for that oriface tube?
Customer: replied 1 month ago.
That looks like evaporator mounting one. Now that we know that the screen faces the condenser, I would need a condenser mounting with a black screen end correct?

I'm basing it off this tsb which calls for that part #

Customer: replied 1 month ago.
The first design has the part # that you sent. The second design looks like what came out of the line that I am going to use. What me would you recommend?
Customer: replied 1 month ago.

155151 looks to match the one you showed on the tire. Both that and the black and white one have the same orifice size of .072. There's a very small diameter difference as seen HERE and HERE

Customer: replied 1 month ago.
Is the 155151 what I need then, regardless whether it is black or white. What I am installing is a 1st design setup correct?

Correct, this is 1st design with orifice in liquid line. 2nd design is the orifice right in the condenser outlet.

Customer: replied 1 month ago.
I bought a new second design condenser, compressor lines, high side line to evaporator core, accumulator. I checked the fittings for both the donor truck's and new second design lines from condenser to evaporator core. They are identical. I didn't measure them with a micrometer, but the second design installed, threaded into the evaporator core just like the first design does. Now that we have established that both the first and second design setup both have the oriface tube with the screen pointing towards the condenser, I should be good to use the second design condenser, oriface tube and lines correct?
Customer: replied 1 month ago.
I checked everything for fit. It matches up.

Great, you are good to go then on using the second design.