ok, ok, I looked up prices on a drier, and valve, not as bad as I was thinking.
r-134 conversion
- Thread starter Monkeyed
- Start date
ok, ok, I looked up prices on a drier, and valve, not as bad as I was thinking.
ok, so pulling 22(ish)psi vacuum, going to leave it like that for a while and make sure there are no leaks
with the harbor freight special hooked up it pulls nearly 30psi, but keeps my compressor running non stop, I'll cycle it for a while to get any moisture out, then, on to charging.
with the harbor freight special hooked up it pulls nearly 30psi, but keeps my compressor running non stop, I'll cycle it for a while to get any moisture out, then, on to charging.
22 inches vac is not good enough! It may work for a while but there will still be air and moisture in the system. Any moisture in the system becomes corrosive and will destroy parts. You need to do it correctly or expect to do it again. If the dryer has absorbed moisture from being open too long, or moisture in the system it can plug up or fall apart internally causing valve, bearing or orifice failure. If you get it down to 30 inches and hold it there overnight you MIGHT get away with it.
I replaced the drier right before I did this. The compressor cycles on and there are no bubbles in the sight glass. Feels like it's drying the air, but doesn't feel terribly cold. I haven't stuck a thermometer in the vent yet, but I'm guessing closer to 50, or 60 than 40
Usually the best you can get is a drop of ~20 degrees from the inlet air temp, use a thermometer by the opening by passenger side footwell to get inlet temp, and in vent for outlet temp. I have seen some do better than 20 degrees but not many. (used to do this for a living) If it is 80+ degrees outside and the car is in the sun 40-50 degrees is fantastic!
tim berry
Well-Known Member
Ive seen some opinions on the sight glass having bubbles with a134 some say none some say its normal i personaly have vaccumed the system down to thirty inches new recever/ dryer and filled with 24 ounces of 134 also replaced the codensor this one has smaller and more tubes than the original one . On max ac at 87 deg. 80% humity i did achieve 37 degree vent temps . Jasper the evaporator valve is adjustable look with a mirror at the bottom of it and you will see a round button looking thing with a flat side move that so that the flat spot is in line with the valve ( front to back ) i had the same
problem with the high pressure lines being to hot and actualy melted the o rings . When i opended the expantion valve up it works normaly hope this helps now we need to get the difinitive answer on the bubbles in the sight glass good luck .
problem with the high pressure lines being to hot and actualy melted the o rings . When i opended the expantion valve up it works normaly hope this helps now we need to get the difinitive answer on the bubbles in the sight glass good luck .
Here your answer- Sight glasses are not the correct way to charge aN a/c system. R22 is a single compound refrigerant with one boiling point so sight glasses, if used properly, can be used to charge a system "close enough". R134a is a blend of different chemicals to average a boiling point. Some chemicals will boil sooner causing bubbles in sight glass, this is normal. To charge the system correctly sub cooling in liquid line must be known. And when adjusting txv super heat must be known. Typically r134a charge will be 70 to 90% of r12 charge. To correctly charge a/c system needs to be evacuated of all air and moisture, evaporator and condenser coils need to be clean, fan needs to be on high and super heat and sub cooling need to be known. Sight glass should only be used as a reference. Also when changing refrigerant 95% of oil needs to be changed. This usually requires 3 oil changes while operating r12 between changes. This never gets done because if you have that much r12 there would be no need to retrofit. What I do is flush system with r11x flush to remove as much oil as possable, then purge with nitrogen, followed with a good evacuation. Any mineral oil left in system will collect in evaporator and reduce capacity. Temperature drops across evaporator will fluctuate depending on where readings are taken, typically 20-25 degrees cooler. If charging by sight glass only, add a little at a time and wait a few minutes for pressures to stabilize and stop as soon as glass is full. Check pressures (you can find a reference chart on line), and check temperature at vents. Hope this helps, good luck.
after swaping the drier I wasn't getting a good seal with the old stamped washer, I replaced that, pulled a vacuum and charged it until the compressor started cycling on and off, then removed a bit. with the max a/c on, in 90+ 100% humidity the temp in the vents is close to 30*. now my problem is that sometimes when I switch to bi-level or just vent the temp in the vent climbs to 110+. did that this morning when it was 50* out. switch a/c on and it drops back down a bit to about 60 ish, turn max on and it's in the sub 40s again.
I'm thinking the blend door is gummed up like so many other things on this car and sticking. 2 questions, 1st is it vacuum operated, and 2nd do you have to take the dash out to get to it?
8v-of-fury
Well-Known Member
So a cycling compressor mean low refrigerant? and thus likely the compressor is heating up too much and shutting down?
Aspen500
Well-Known Member
The compressor cycles off when the low side pressure drops below a certain level (usually around 20 lbs). Excessive cycling indicates low refrigerant and a leak somewhere. During normal operation, the compressor cycles off to prevent the evaporator from getting too cold and freezing the condensation on clutch cycling type systems.
8v-of-fury
Well-Known Member
What is excessive and what is normal operation though? Lol
Like excessive being on and off like 2-3 times a minute?
Like excessive being on and off like 2-3 times a minute?
Aspen500
Well-Known Member
All depends on the ambient temp. If it's 40 degrees out (like when the defroster mode is selected), it'll cycle a whole lot more than when it's 100 out. At colder temps it will be off more than on and vice versa for hot days. 2-3 times a minute isn't excessive. If the air outlet temp in the car is cold (between 35 and 45 degrees depending on outside temp and humidity), everything is fine. If the charge is low, the air temp will be too warm.
Just an example: Driving home from work this evening the compressor clutch in my Dakota was cycling on and off at least 3 times a minute, maybe more. Temp of 80 and a humidity that felt almost the same number, ice cold air out of the vents.
Probably has been gone over already in this thread but I'm too darn lazy to check, when converting from R-12 to R-134a, the rule of thumb is to charge with only 80% of the specified R-12 capacity. My Aspen has a spec of 32 oz of R-12 and I charged it with 27 oz of R-134a and get mid 30's for air temp on a typical summer day (say 85 degrees out) and there are bubbles in the sight glass which is normal. Very few cars that use R134a from the factory have a sight glass but those that do also have some bubbles.
Just an example: Driving home from work this evening the compressor clutch in my Dakota was cycling on and off at least 3 times a minute, maybe more. Temp of 80 and a humidity that felt almost the same number, ice cold air out of the vents.
Probably has been gone over already in this thread but I'm too darn lazy to check, when converting from R-12 to R-134a, the rule of thumb is to charge with only 80% of the specified R-12 capacity. My Aspen has a spec of 32 oz of R-12 and I charged it with 27 oz of R-134a and get mid 30's for air temp on a typical summer day (say 85 degrees out) and there are bubbles in the sight glass which is normal. Very few cars that use R134a from the factory have a sight glass but those that do also have some bubbles.
8v-of-fury
Well-Known Member
Thank-you Aspen, that was very helpful information.
It can also cycle from too much, there is a High pressure safety switch, the compressor will raise the pressure too high, then shut off while until it returns to a safe level, then start again. I overfilled mine, it still blew cold and I never got around to letting enough out to just keep the compressor running, very scientific, I know..
I found out the reason my temps were all over the place was that the blend door motor cable connection was partially cracked from age, so it only had intermittent contact. I put a zip tie around it and that cured it.
Sometime over the winter the a/c decided to stop working again while I wasn't looking, so I'll probably have to start this process all over again, preferably before it gets to be 90* and 90 humidity out..
Jack Meoff
Mopar Maniac
Mine has a slow leak so it's time for a recharge.
I put the guage on mine and it seemed high, not sure how more stuff could have gotten in there, I park it in the garage so I only used the defrost once or twice all winter.. maybe a valve got stuck? going to have to find a way to make some time time for a half-assed diagnosis on it lol :eusa_wall: tempted to evacuate all the refridgerant and start over..
Aspen500
Well-Known Member
That's what we do here at work a lot of the time. Recover the system, evacuate and recharge with the specified amount. Only way to know for sure. More and more lately we do this. Those "home" A/C recharge deals they sell at stores cause all sorts of problems. We find quite a few overcharged systems.
I don't know if you got this resolved or not, I didn't notice it before. I'm not an expert on it, but from physics, compression generates heat, that's why a propane tank gets frost on the outside of it when it's being used, it's decompressing.. So theoretically that might be normal..
incidentally that's how a/c works, the compressor creates the high pressure"hot" side, and then another part of the system rapidly decompresses it making the "cold" side..
Aspen500
Well-Known Member
Yes, the compressor will get hot, very hot, like burn yourself if you touch it hot. The high side lines will be way too hot to touch also. Once it changes state from liquid to gas, it can absorb the heat from the evaporator and send it through the condenser to give up it's heat to the air and start the process over. Remember, air conditioning doesn't make cold, it adsorbs heat so the air feels cold. It's that whole latent heat of evaporation thing, a bunch of physics and to explain it thoroughly would take a couple pages of typing, lol.
You need to know HOW an A/C system works before you can diag repair etc. R134 runs higher pressure than R12. The "redtek" kits are a mistake and are typically R22. most shops wont touch an A/C topped up or filled with that, as it will contaminate their tanks ( your old Freon is recycled) or ruin a $5000 machine ( we sample and test the Freon before recycling. Vacuuming the system is to lower the boiling point of water/moisture to remove it from the system..it WILL NOT remove contaminates. An A/C flush procedure of special liquids cleans out the system. Vacuum is also used as a rudimentary way of leak testing, but is old school and shouldn't really be used as a diagnostic tool. Charging the system to 250 psig with an inert gas ( nitrogen) is the only real way. ( testing a system that never see's a negative psig is useless, unless there is a large leak...you need to test a pressure system with pressure)...once you know what is happening where and when, then you know what the gauges are telling you, and they read PSIG not true PSI ( yes there is a difference, and depending on where you live it can be significant). Depending on where it is placed in the system will tell you if you have an accumulator, or receiver/dryer, which its main purpose is to make sure no liquid makes it to the compressor ( it cant compress liquid and will fail if it tries to compress to much liquid). If the system is opened for any reason, the reciever/dryer needs to be replaced ( the desiccant with suck moisture right out of the air), an accumulator doesn't need to be . If the compressor fails, you should replace the condenser and expansion valve as no amount of flushing will get out the metal shards, which will work their way back to the compressor and cause it to fail again, in which case everything needs replacing. You charge the system to the factory rec weight ( converting to R134 requires a conversion of the weight) and use the pressure readings to fine tune. Sight tubes are again an old school, very inaccurate method of diag. Static, non running pressure alone can tell you more
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