Can someone clear up my orifice tube questions?

Hi guys,
I am working on getting my parts together to fix the AC in my 92 and convert to 134a. My question is on orifice tubes. They only list a red one (cheap) and a variable one (expensive) for my vehicle at the parts store. I had heard from someone that I needed to change to a blue one. Can someone enlighten me on what the difference is, which one I need, and (if it's the blue one) how to get one? Thanks so much in advance if anyone can help me out.
Ryan

Each color is a different orifice size.

Ford
Orifice Size

Blue .067"
Red .062"
Orange .057"
Green .052"
Brown .047"

The blue one will build less high side pressue, but it won't cool as well at idle. R134 will run a little higher pressures than R12, so maybe that's why they told you to get the blue. On the freeway, you might not notice much difference in vent temp, but the compressor will be working harder with the red one, but I don't know how that would affect it's life.

I've been using the VOV valve for a few years now, but up until a couple of weeks ago, my a/c system wasn't really charged properly. It was OK, but not great. See my BII thread in this forum. I flushed all the old oil out and replaced my drier and vacuumed for an hour. Filled with 12oz oil and a little over two cans of R134 and it's working really well now. At first I could only get down to 50 degree vent temp, but it turns out my heater door wasn't shutting 100% and was keeping it from working as well as it could. I cut off coolant flow to the heater core and now it's getting down to 40 degrees in 100+ outside temp!

I'd go ahead and spend just a little more on the variable valve. It's reliable and will give you better performance at idle and will be easier on the comrpessor when moving. It works a lot like an expansion valve, just better technology. Also, do not re-use the accumulator, buy a new one. Don't pull the plugs on it until the minute you will be hooking it to the lines.

Hey thanks for the reply, I had read your post, but that clears it up for me a lot. I did already buy the accumulator, that was the first thing I bought, and of course I haven't touched the plugs. My vacuum pump and manifold gauge set should be in the mail. If I end up re-using my compressor, do you know of a good procedure for cleaning the old oil out of it? I don't know why my system doesn't work since it has never worked since I bought the truck, but it had no charge in it, so I figure its probably a leak. My plan is to replace the hose and o-rings, vacuum it down, listen for obvious leaks, if nothing, then charge it and see how it goes.

You probably don't need to replace any hoses unless they're cracked or something. Best way to clean out the compresser is to pull it out and turn it by hand while the oil is draining from the inlet/outlet. Just move it around while turning it until the oil stops coming out. Then add a few ounces to the low side and turn it so it will go through and dump that out. Don't put any solvent in the compresser!

I got my a/c flush from here. http://www.wholesalepartsandtools.com/ Cheapest place I could find and they shipped my stuff real quick. Flush was only $14. Also, in their blowout special section I got a retrofit kit that came with 8oz of ester oil for $6. I went ahead and replaed the fittings since they have new o-rings on them and it was cheap. Also got my vacuum pump oil from them, you want to change it after every use. Old oil in the vacuum pump will keep you from pulling as deep a vacuum. Also, I got two of those Tech Chemical Castrol 6419: Castrol EZ Fill A/C Power Boosters, $2 each. That got my oil level up to 12oz.

To flush, just get some of that clear vinyl hose from Home Depot or Ace. Disconnect the a/c hose at the evaperator inlet. You'll need the special hose disconnect tools to pull some of the fittings apart. You'll find them at any auto parts store. Get the vinyl hose size that will fit over the a/c hose ends, use a funnel to pour the flush into the hose and into the condenser and let it sit for 10 min. Then blow air through for a couple of minutes. Pull the orifice tube and do the same for the evaporator.

After you flush the system, use a shorter piece of the vinyl hose and add 2oz to the condenser inlet, 2oz in the evap, 2oz in the accumulator, and pour 6oz into the compresser. Or, if you do it like I did, put 6oz in the compresser and 2 in the accumulator and add the two oil charge "boosters" after you put 1 can of R134 in.

If you plan to keep the truck for a while longer, I'd go ahead and get a new seal kit for the compresser since everything will already be taken apart. I put one in mine 3-4 years ago and it hasn't leaked since. You can tell if yours is leaking if there's a lot of dark greasy stuff behind the pulley.

As for a leak, you'll quickly know if there's one if it won't hold a vacuum. Just make sure you put a little a/c oil on the o-rings before putting the fittings together. Also, for the ones that screw together, put the o-ring on the shoulder of the hose, push the two sides together and hold them together while screwing the nut down. Make sure the o-ring slides in perfectly before screwing together. If you don't hold the fitting together, it might pull apart slightly while scewing them together and pinch the o-ring, causing it to leak. You can tell very quickly if there's a leak after about 10 min of vacuum, close the gauges, turn the pump off and watch it for about 5 min. If the vacuum needle doesn't move, turn the pump back on and open the valves back up and vacuum for another 50 min. After vacuuming for an hour, close the gauge valves, THEN turn the vacuum pump off. Don't pull the gauges off or the vacuum will be lost. Let it sit for 10 min and make double sure there's no leak. You should have around 29inHg. After that, hook up your can of R134, pierce it and slightly unscrew the hose at the gauge manifold until you hear a hissing sound. This will purge that line of air/moisture. Tighten it back and open the low side valve and let the R134 pressurize the system. Start the engine and put the blower on max and let it pull all the freon out of the can. Do the same with another can and you should be good to go. No need to purge between cans since the hose will be under pressure and no air will be pulled in like when it was under a vacuum.

Good luck!

Hey thanks for the post, it takes some time to type out detailed responses like that and I sure appreciate it. My vacuum pump and all that are in the mail, so I will tackle this when they get here and I will let you know how it turns out. Again, thanks so much for the help.
Ryan

I have the red orifice tube in my 1990 and it seems to work fine on 134a (the tech guy who I happened to have charge it even commented the pressures looked real good as he was filling it).

Thanks!

Kurt Thanks for the write-up man. The priority of getting my A/C fixed is going up with each 100+ degree day. With that info, I'm gonna give it a whirl this weekend.

Good post; excellent info!