Orifice Tube Question, R134 to R12 conversion

[JOEZ33]

I work in aviation and we still use R12 on a daily basis. So it's available with no problem. I live in a pretty frikin hot environment and the colder the AC the better. I decided to upgrade to R12 in my 98 explorer.

I removed the R134a with our 134 machine, then filled with R12. Normally when doing a 12 to 134 conversion you use only 80% of the old amount of freon, so a 1 lb R12 system gets refilled with .8 LB of R134. I did the math in reverse and appropriately filled slightly more R12 than the under hood sticker.

My problem is that the orifice tube is allowing too much volume to pass through it, and I'm not getting much of a pressure split between low and high sides. I'm only getting 125 psi high side and 30 psi low side, and it constantly freezes up unless I run the blower at full blast. When I add more freon its not as cold, then suddenly freezes up on the highway again.

My question is whether they make other orifice tubes that are more restrictive, maybe from older R12 trucks. If so, what's the part number?

 

[ShadyGrady]

Ask parts store for orifice tube for 1992 Ford Explorer...they ran r12. use ester oil too...it is the universal A/C oil...just flush your system...I use denatured alcohol or brake cleaner followed by a good blow with compressed air...and absorbent mats to catch the crap on the other end...it is messy to go line by line/section by section...but it is clean when you are done...do not clean the accumulator with that stuff...it will mix with any oil and not come out...only lines and things that can be blown out(I am sure you know all this but just to be sure, I mention it), re-seal, and vac it real good, extra good, and then do the fill to the spec for an R12 vehicle...see the Chilton's or a Haynes for that year for specs...Capacity can be close...R12 is a bit more forgiving...look for good gauge readings and the like...good luck! You were close on yours...just a bit higher like 225 on the high side if I remember right, the low is OK if range is 28 to 38 for R12 If I remember right...30 was good. Read a Haynes or Chilton's. gotta get all the R134a out of system...all or you will have problems...most folk change accumulator...but you may know a few more tricks or see what can work and will not work...I never let the two mix, I never got away with it...the desiccant would never purge all the way for me. I hope you have better luck. strikes me odd cuz I use the tube for the R12 with the R134a in system, and it is fine for me...42 degree at vent. I heard that if you leave system open for 24 to 48 hours...all the freon will escape from the oil and you can put what ever you want as long as you vac it good, but I never try it. I not saying this IS YOUR problem...but if you still get low High side readings...your compressor could be going bad...again good luck...and I hope to not be condescending...I just want to offer as much info I can to give good help. My buddy uses Fridge C, he says it is the coldest...he says 38 at vent...see your local Car Quest or NAPA for it and how to use it...I not have a clue about it...but it is SUPPOSED to be the whip of COLD.

 

[JOEZ33]

I'm hoping that a more restrictive orifice tube will cause a lower low side and higher high side reading. When parked the low side is about 40 psi and high is 120. Then after a while driving the low side works it's way to around 30, then the system freezes up for a minute, then works intermittently. I'm pretty sure it's flooding the evaporator with so much freon that it can't absorb all the heat from the cabin unless the fan's on full blast. That's why it only works for a few minutes when the interior is smoking hot, and freezes up as soon as the cab starts to cool off.

Ever heard of R409?

 

[ShadyGrady]

I think you are getting warm on it bro...you just got to experiment with it till you get it right...I not sure it is more restrictive or not...it works with r-12 and r 134a for this vehicle so it just may be your ticket...I converted it to r134a a few years ago...I did nothing special...just flushed it, put new r-12 accumulator&orifice tube(meaning the OEM units for this truck) and charged it 1 for 1 capacity and it is cold 42(f) degrees at vent...but...big but...when I get close to capacity I start reading the gauges and checking the vent temps...sort of a guess on if I an a ounce or 2 shy or over exactly as I am using the 12 oz cans and I can not get an exact amount that I need...and I always have some left over...I an close to the same oem amount needed from factory specs...and not sure as to what that is anymore...truck is in fair to good shape and I basically only needed to charge it twice since I own it...once when I bought it, and once when I replaced the compressor...so it is not like i charge it a lot...i do however push a lot of gas each year for friends...and I follow the same personal rules for them as for myself...I try to charge for capacity and when close to that amount...I read gauges...and confirm with vent temps vs time to cool down...with consideration for outside temp and humidity and such...I no exact pro at it though...just trying to get better, and help some folks at same time...practice makes perfect...right?

I thought R409 was popular in other countries, maybe Canada? I not know anything about it yet...just seen it in reading here and there.

 

[JOEZ33]

R409 is a direct drop in replacement for R12 and is 20% more efficient- BUT- is not approved for use in moving vehicles. I don't know why, but they only want it being used in refrigeration equipment. I think it has some of the "bad" environmental stuff in it, which is why it works so well.

When using it, people who just haphazardly put it in their system end up with incorrect pressures. This is because they need to run slightly less than the required amount for the R12. If it's an R12 system using 2 LBs then it should be filled with something like 1.8 LBs of R409a to get the proper affect and pressures.

 

[JOEZ33]

Well apparently they all use the same exact part number orifice tube. The a/c system in my 98 must have a bigger capacity condenser, or something else is causing the high side psi to be very low. I'll recycle the r12 out and convert back to R134 again. I know it was usually around 175 -200 high side and 35-45 low side with r134a, which is where it was immediately before converting to R12.

 

[ShadyGrady]

Sorry I could not help...orifice tubes go by temp. and supposed to be gas specified. Did you charge according to pressures? Anyway thanks for the R409 info. Check out VIOT.com for your A/C tools.

 

[wearyarrow]

R409 is highly flammable, that is why it should not be used in a moving vehicle. Bad accident problems. FYI

 

[allmyEXes]

OLD POST ALERT!