A/C orifice tube assy.

datkinsonsr

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I have the factory installed system that has been changed over to R134A. Before my problems started, I was getting 38 to 40 degrees from the ducts, 28psi low/225psi high, ambient 98 degrees. Because I drive a lot of city stop and go, I decided to go to a variable orifice tube to improve cooling. Worked fine for a couple of days and then the orifice tube blew apart. Top half of tube was missing. Cleaned system and went back to the original fixed tube. Note: when conversion was done, no high pressure switch was installed. I have heard this is needed, but am not sure. Possible high pressure problem? Also, I see that there are different color orifice tubes for this system, but have not been able to find out what the different colors represent. Which color is correct for this system? I would prefer to have the variable orifice tube if I can get this done correctly. Anyone here with experience on this one?
 

chris142

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I do automotive AC for a living and we gave up on the variable Orifice tubes years ago. Nothin but trouble from them. The colors represent the size of the orifice. The Blue tube is slightly larger(.67) than the Red tube(.62). The Red tube usually works well in our trucks. Thats whats in mine and it works great here in the desert.

Excessive high side pressures can be caused by many things. Faulty Fan clutch, overcharged,dirt in the condensor fins, internally contaminated condenser etc. The R134a charge should be 85% of the R12 charge. My 87 calls for 3.25 lbs of R12, this equates to 2.75 lbs R134a.
 

itsacrazyasian

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I do automotive AC for a living and we gave up on the variable Orifice tubes years ago. Nothin but trouble from them. The colors represent the size of the orifice. The Blue tube is slightly larger(.67) than the Red tube(.62). The Red tube usually works well in our trucks. Thats whats in mine and it works great here in the desert.

Excessive high side pressures can be caused by many things. Faulty Fan clutch, overcharged,dirt in the condensor fins, internally contaminated condenser etc. The R134a charge should be 85% of the R12 charge. My 87 calls for 3.25 lbs of R12, this equates to 2.75 lbs R134a.

Blue orfice was for R12. Red is what our body style trucks got with R134a. Works well for most ambient conditions. 225 psi on the high side on for that ambient is just fine.
 

FordGuy100

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What conditions does it not work in? I have to re-do my whole system as my stock AC compressor gave up the ghost. I got a junkyard compressor but am a bit Leary of putting it in there for it to fail on my as well :although it looks to be in good condition. I had a VOV in my truck when it all happened and duct temps were low enough that I could easily fog up the windows because of the humidity. Think it was red and I ordered it from rockauto.

On the AC subject, anyone use one of those AC vacuum units that run off compressed air? They are much less expensive but I don't know how well they work.
 

jhnlennon

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On the AC subject, anyone use one of those AC vacuum units that run off compressed air? They are much less expensive but I don't know how well they work.

I have used one and they will not pull down enough vacuum to boil water out of the system. Thats pretty much the whole point of pulling a vacuum. Harbor freight has some decent prices on vacuum pumps, especially if you can find one of their 20% of one item coupons...
 

itsacrazyasian

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They work well enough for the limited use that you'll be doing. I keep one as a backup in my toolbox FWIW. The VOV aren't color coded. They're black. Red means fixed orifice. I wouldn't **** around with a junkyard compressor when a new compressor isn't crazy money. I bought a HCC or Halla climate compressor (OEM for many manufacturers now) for my buddies Crown Victoria for a whopping 160. Came prefilled with 8oz of pag oil. Changed drier, orifice tube, flushed condenser and away he went. all the parts minus R134a came out to about 190. Could have been cheaper but i've had issues with the no name driers fitting properly so i opted to order a 4 seasons unit. Same place i order my ac parts from had a offshore compressor new for 109... But those are just junk.
 

itsacrazyasian

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I have used one and they will not pull down enough vacuum to boil water out of the system. Thats pretty much the whole point of pulling a vacuum. Harbor freight has some decent prices on vacuum pumps, especially if you can find one of their 20% of one item coupons...

My backup air operated pump is made by FJC. Will pull to 30inHg on a typical mobile hvac system in about 4 minutes. It uses quite a bit of air though. I had to use it a few times when my recovery machine kicked the bucket. No issues at all, just takes much longer.
 

jhnlennon

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My backup air operated pump is made by FJC. Will pull to 30inHg on a typical mobile hvac system in about 4 minutes. It uses quite a bit of air though. I had to use it a few times when my recovery machine kicked the bucket. No issues at all, just takes much longer.

2 harbor freight pumps, and a one ebay model would barely reach 27 inHg in my experiance. The cheap ones you see on ebay and harbor freight are a waste of money.

The general concensus is that a air operated vacuum pump WILL NOT pull a hard enough vacuum to boil water out of a system.

http://aircondition.com/tech/questions/38/Air-Powered-A{47}C-Vacuum-Pumps
 
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opusd2

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I do a lot of HVAC on my own now, and still have the Robinaire I bought when I was doing a lot of new construction for contractors. When it comes to AC, it pays to go the extra step, spend a little bit more money to get the good parts, and keep it simple and safe with at least a HIGH cutout, but a low one is good too. Always replace the drier, orifice, and O-rings when working on a system. I am not a huge fan of VRVs, I prefer to go with cutouts but that's my choice.

And when I pull a vacuum on a car now, I still pull for a couple of hours to boil as much moisture as possible. And I still do a test charge with N to make sure there aren't any leaks in the system, a throwback to my old days on new installs and retrofits in residential. And when getting a pump, don't go out and buy the biggest CFM unit you find. On small systems they've been more of a problem than a help. I got rid of mine since I don't do any chillers anymore, and just kept the small pump. And even though this may be overkill for the average homeowner/small mechanic, a good gauge set with decent hoses are incredibly helpful. But I'm probably talking unnecessarily here about equipment for most. And in WI I have yet to find an auto store that sells 134, which is crap. I have my license so I could get it in bulk if I want, but 20# of the stuff would take forever to get rid of. Well, legally.
 

jhnlennon

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And in WI I have yet to find an auto store that sells 134, which is crap. I have my license so I could get it in bulk if I want, but 20# of the stuff would take forever to get rid of. Well, legally.

Wisco recently changed the law that banned the public sale of r134(last state in the union to do so). Every part store in the state should be selling it now. My local Oriellys has as many cans of it as you want in stock. Still cheaper to get it over the net though...
 

boxathey

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I have a yellow jacket transducer to measure the vacuum in hvac units. on 40 ton industrial units I bring it down to 3 to 400 microns which sometimes takes many hours to accomplish depending on how much moisture is in the lines my friend has 1 of those air operated vacuum pumps in just for ***** and giggles when he was getting ready to replace his compressor, I hooked my vacuum transducer up in line with it to see what it could produce it did make it to 29.5 inhg , but it wouldn't go any more than like 2200 microns, milltorr. so I personally wouldn't use 1, unless I was in a pinch. and I agree a good quality vacuum pump goes a long way I have an older robinare that I use to use all the time and it still in working order. 2 years ago I purchased a 6 cfm 2 stage master cool unit that I use now but I do a lot of larger units anywhere from 15 all the way up to 50 ton chiller and hvac units
 

FordGuy100

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Yeah I picked up the compressor for like $10 so I wasn't to worried about it. Will definatly spring for a new one then.

Seems as though the compressed air pumps don't do the job as well as needed. If I was living in the desert perhaps, but humidity is to high here to do that.
 

opusd2

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Yeah I like to pump down to as few microns as possible and will run the pump for extended periods to do so. I have an older meter that I hook into my 4 hose Yellowjacket setup that helps measure the level. I'll tell you, it was an education a few years back. I'm used to pulling down to damn near 0, but when I moved out to Wyoming and did a bunch of AC I was lucky to see around 20, but then again I was working at 8,000ft as opposed to 315ft.

And I used to have a nice 10 cfm unit for the big chillers, kept a company 6 cfm in the work van, and had my own 3 cfm Robinaire. That's the only one I kept since I just do a lot of smaller jobs now and don't need to pull down a 60 ton unit.

Man, I can remember having to change out a compressor once on a 60 ton unit on a military base. That pump was fricken HUGE! It tool 4 of us to hump the old one out and put set the new one in. OK, so a forklift helped a little... Certainly different than a vehicle.

And it didn't matter if the auto stores kept the refrigerant in stock or not, I have the credentials to get the stuff, but who wants to hang on to a 30# bottle of 134? Though I am sure if I went through the vehicles on the farm and of my own, i could certainly empty it out twice. And that includes a couple of tractors. That reminds me, the neighbor has a Ford that he wants charged up. I bet I could retrofit, flush, and recharge it with 134 the only problem is he is so damn cheap it would take years to get the money from him. So, I won't mention I can do that for him. I remember how long it took him to pay my brother and me for rebuilding his IH 806 a couple of years back. I definitely need to start putting liens on the work...
 

opusd2

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Boy I went off subject. Anyway, I think I will wait until IOLA to get some 134 along with some 12oz cans of ****** R12 which you can luck out and get for $20 a can like I saw two years ago. Though I doubt he has any left. A buddy of mine's dad died this spring, and he had dozens of cans of R12 and R12 with oil charge stacked up in his garage yet. I'd feel like an ass asking if they'd sell a few of them so I could keep at least one vehicle stock. I just don't feel like changing out the compressor at the moment. Though in the long run it WOULD be cheaper to convert.
 

boxathey

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largest ive worked on was a couple 50 ton units. I bet the 60 ton had one hell of a compressor. and 80lbs of freon.
 

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