1985 Corvette orifice tube

[Jim T.]

Using the information in my 1985's shop manual I disconnected the air condition line going to the evaporator inlet to remove/replace the orifice tube. There is no orifice tube in my 85's evaporator inlet. Using a flash light to look inside the evaporator inlet I can see no orifice tube looking all the way to the evaporator's core area. There is no orifice tube in the line I disconnected going to the evaporator's inlet.
Any one have any experience with an 1985 Corvette in removing the orifice tube?

My 1985's shop manual even states the installation of the orifice tube inside the evaporator's inlet pipe with the orifice tubes "shorter screen end first" inserted first.

Where is my 1985's orifice tube? I have owned my 85 since 1992 and no one has done any work on my 1985's air conditioning system. I bought my 85 from the original owner and was given all the paper invoices for work on my 85 including warranty work.

[Joe C.]

Re: 1985 Corvette orifice tube

Remove the aluminum tube from the evap inlet. Inside the inlet you should find a screen/tube. It should be there, as I have one in my 1985's evaporator inlet. I can't say more than that. I am still charging with R12, and the reason I went there was because I installed a new compressor. The screen was clean and I DID NOT replace the accumulator.

Why are you looking for the part? Does your unit blow cold? Is it retrofitted with 134a? If so, then maybe the retrofit requires elimination of the orifice?

[Jim T.]

Re: 1985 Corvette orifice tube

Joe I am replacing my 1985's air conditioning compressor as well. I did remove the aluminum tube from my 85's evaporator's inlet just like the shop manual said. The orifice tube was not there. I am going to recharge my 85's air conditioning system with R12 like you. I am glad to hear that your orifice tube was clean. Thank you for confirming that the orifice tube is installed in your 1985 in the evaporator inlet. the shop manual says this is where the orifice tube is located. I do not know what has happened to my 85's orifice tube that should be in the evaporators inlet. The system needs the orifice tube to operate correctly. Where is my 85's orifice tube?

[Douglas L.]

Re: 1985 Corvette orifice tube

GM usually puts the orifice tube in the evaporator inlet but sometimes they put them in the high side line between condensor and the evaporator. When placed in the alternative location, there is usually a "dent" in the line to prevent it from moving. Another alternative is that the orifice tube has fallen apart and migrated into the evaporator, I've only seen it a few times but it does happen.
Good Luck, Doug

[Joe C.]

Re: 1985 Corvette orifice tube

Joe I am replacing my 1985's air conditioning compressor as well. I did remove the aluminum tube from my 85's evaporator's inlet just like the shop manual said. The orifice tube was not there. I am going to recharge my 85's air conditioning system with R12 like you. I am glad to hear that your orifice tube was clean. Thank you for confirming that the orifice tube is installed in your 1985 in the evaporator inlet. the shop manual says this is where the orifice tube is located. I do not know what has happened to my 85's orifice tube that should be in the evaporators inlet. The system needs the orifice tube to operate correctly. Where is my 85's orifice tube?

I wish I could answer your question. If you are still using R12, and the system blew cold while you owned the car, then it has to be somewhere. It has to be on the high side, somewhere between the compressor discharge and the evap inlet. If you leave the system open for too long while searching for it, you risk contaminating the accumulator with moisture. The purpose of the restriction is to throttle the high pressure gas so that it sheds heat and drops dramatically in temperature. If there is no orifice in place "somewhere" between the high side of the compressor and the inlet to the evaporator, then the system would NEVER have delivered cold air. If you cannot attest to that fact, then rest assured that the orifice/screen must be present in a different location as stated by another poster.

My vote is to leave it alone, as long as you have the opened ends plugged in some manner. If you're replacing the compressor due to leaks and oil slinging, there's a high probability that the screen isn't clogged with trash. If you don't want to replace the irreplaceable accumulator, then button it up, evacuate and install the new Freon and mineral oil to the system.

Best of luck to you.
Joe C

[Joe L.]

Re: 1985 Corvette orifice tube

I

If you don't want to replace the irreplaceable accumulator, then button it up, evacuate and install the new Freon and mineral oil to the system.

Best of luck to you.
Joe C

Joe------


What's so irreplaceable about the accumulator?

(By the way, I'm making this post while flying at 38,000 feet over Ohio)

[Jim T.]

Re: 1985 Corvette orifice tube

Joe did you replace your 85's compressor with a new AC Delco compressor? My 85 has always had R12 and did deliver cold air. The change was not producing the cold air like it used to. I decided to replace the compressor, accumulator, and orifice tube. I do not see another place for an orifice tube between the compressor and the evaporator. The other location for a orifice tube that Douglas mentioned is something to explore, I hope it did not end up in the evaporator.

[Joe C.]

Re: 1985 Corvette orifice tube

Joe------


What's so irreplaceable about the accumulator?

(By the way, I'm making this post while flying at 38,000 feet over Ohio)

Are you in a plane?

I didn't see one that looks original.

[Joe C.]

Re: 1985 Corvette orifice tube

Joe did you replace your 85's compressor with a new AC Delco compressor? My 85 has always had R12 and did deliver cold air. The change was not producing the cold air like it used to. I decided to replace the compressor, accumulator, and orifice tube. I do not see another place for an orifice tube between the compressor and the evaporator. The other location for a orifice tube that Douglas mentioned is something to explore, I hope it did not end up in the evaporator.

Yes, I did. It's not an exact replica but close enough for me. It doesn't sling oil, blows ice cold so I'm very happy.

I hope that you clear up the mysterious missing o-tube. Good luck.

PS: You might need a set of manifold gauges to measure pressures both hi and lo. This might tell you whether or not there's trash somewhere in the system. If you can't find the tube, it might be a good idea to have a pro flush the system for you. Remove and cap the accumulator so you can re use it. Too bad you removed the original, it might have still been OK.

[Jim T.]

Re: 1985 Corvette orifice tube

Joe on my way to work this morning I stopped at the Chevy dealer and spoke to a man in the parts department and asked to see what he could bring up on his computer concerning my 1985's orifice placement. He was able to get a picture of the 85's air conditioning system showing the placement of the orifice tube in the evaporators inlet. I told him my 85 did not have a orifice tube in the evaporators inlet. He then read some of the narrative information about the system and found something very helpful. Seems that my 85 must have a orifice tube in the R12 line that attaches to the condenser. I had noticed yesterday while installing my new compressor and the valve cover that the R12 line to the condenser had a big enough bulge in it to house an orifice tube. I was going to separate the R12 line from the condenser to check it out but declined because I did not have any o-rings with the new orifice tube and decided not to disturb the connections. Do you have a GM shop manual for your 1985?
Due to work I may not be able to work on the 85 until WED or Thursday.

[Joe C.]

Re: 1985 Corvette orifice tube

Yes, I have the 1985 Shop Manual.

[Jim T.]

Re: 1985 Corvette orifice tube

Joe in your 1985 shop manual if you will take a look at page 1B-2. In the bottom photo the picture shows an R12 line going from the condenser to the evaporator and shows the bulge in the R12 line and has (ORIFICE) written below. In reading the air conditioning section I only saw orifice tube mentioned being in the evaporator inlet during previous readings. I discovered this picture on page 1B-2 yesterday in my 85's shop manual reviewing the air conditioning section again after visiting the parts counter at the Chevy dealership.

[Joe C.]

Re: 1985 Corvette orifice tube

Joe in your 1985 shop manual if you will take a look at page 1B-2. In the bottom photo the picture shows an R12 line going from the condenser to the evaporator and shows the bulge in the R12 line and has (ORIFICE) written below. In reading the air conditioning section I only saw orifice tube mentioned being in the evaporator inlet during previous readings. I discovered this picture on page 1B-2 yesterday in my 85's shop manual reviewing the air conditioning section again after visiting the parts counter at the Chevy dealership.

Jim,
I can tell you that the entire smaller diameter aluminum tube which exits the condenser is hot, and becomes ice cold just before the inlet to the evaporator (lower connection). This is exactly where the screen/orifice insert which I described to you earlier is located. Further, I see no bulge or indentation anywhere on that aluminum tube between the condenser outlet and evap inlet.

Because the tube turns cold at the inlet to the evaporator, I have to say that this is where the throttling takes place to cause the pressure drop and consequent temp drop. So, all that I can conclude is that there is no other orifice tube in my high side line, other than the "orifice" as described in Fig 1B-2. This "orifice tube" also functions as a screen, and if it is missing from your evaporator inlet then I'd suggest replacing it.

You might try contacting the C4 Team Leader who might have more information for you concerning system changes based on production date.

I regret that this is not definitive, albeit, intuitive. You might have a different version refrigeration system as many running changes may have been made. My Corvette was built late in the year, in June 1985.

The Manuals have been known to be inaccurate and this may be the case, as the screen may serve double duty as an orifice throttling device. The illustration is, of course, not to scale, and the bulge as pictured does not exist.

If you send me photos of the small diameter tube which runs from the condenser out to the evaporator in, I'll compare them to mine. If they match, and you didn't already reassemble your sealed system, then you should consider buying a replacement tube prior to evacuating and charging your system.

[Joe L.]

Re: 1985 Corvette orifice tube

Using the information in my 1985's shop manual I disconnected the air condition line going to the evaporator inlet to remove/replace the orifice tube. There is no orifice tube in my 85's evaporator inlet. Using a flash light to look inside the evaporator inlet I can see no orifice tube looking all the way to the evaporator's core area. There is no orifice tube in the line I disconnected going to the evaporator's inlet.
Any one have any experience with an 1985 Corvette in removing the orifice tube?

My 1985's shop manual even states the installation of the orifice tube inside the evaporator's inlet pipe with the orifice tubes "shorter screen end first" inserted first.

Where is my 1985's orifice tube? I have owned my 85 since 1992 and no one has done any work on my 1985's air conditioning system. I bought my 85 from the original owner and was given all the paper invoices for work on my 85 including warranty work.

Jim------


One other related thing to keep in mind: in the aftermarket, including ACDelco, are available automatic adjusting orifice tubes. These cost quite a bit more than the stock-type tube but they might be advisable.

[Jim T.]

Re: 1985 Corvette orifice tube

Orifice tube found. Thanks to Dave Perry and Joe Ciaravino for their e-mails telling me the location of my 85's orifice tube. The orifice tube was found in the vertical R12 line in front of the evaporator. The orifice tube was removed and the screens were clean except for 6-7 minute exceedingly tiny chips of aluminum. New compressor, new accumulator, new orifice tube, new 525 oil, vacuum pumped to 29 inches that held, and new R12 installed. The 85's air conditioning system is cooling now.