A/C flush with nitrogen

Why the nitrogen flush? The only real use for dry nitrogen is to use it for leak checking in conjunction with a small amount of refrigerant.

If you want to remove the old oil residue, use a flushing solution avaiable from the auto parts store, mineral spirits or tetrachloroethylene.

Yeah nitrogen is useful to check for leaks w/o adding referigant.

I use regular solevent with a ac flusher that I have. I always remoove the recever/dryer or accumulator first tho. The solivent is probably not too good for the dessicant bag.

Since you have all the refrigerant out, it might be a good idea to retrofit the system to 134a and put some tracer dye in there. Here at the shop we charge 35/lb for r12. 134 can be had for like 8 bux.

Why do you want to flush the system in the first place?

You cannot purchase Freeze 12 in the US without an EPA 609 MVAC license. I recommend that you do an R134a conversion.

Here goes Rev 2 as they say in the computer business. I have added more detail in view that some of the readers may not have done A/C work before

R134a = $8 a can – takes 2 - 2 ½ cans.
R134a compatible oil = $5 for an 8 oz bottle – better get 2 bottles
Gauge set for recharging = $20-$120 – check out the pawn shops for a bargain before you pay retail.
Vacuum pump – I use an old refrigerator compressor = $20- $40 at used appliance stores, or go to the Dump and get one for free. Be sure to have some R12 compatible oil handy to keep it lubed up properly.
Pump to force cleaning fluid through the system $20-$50 (may use compressed air to do the same thing)
O ring seal kit = $8
R134a charging adapter = $13 ( I cut mine up to use it with the R12 gauge set that I have had for a long time)
Plastic tools to disconnect refrigerant lines - 1/2" & 5/8" = $4 each
Flushing agent - Discount Auto Parts has some flushing solvent in a 1 gallon plastic bottle - try that first Or use Mineral spirits = $3 a gallon, tetrachloroethylene =$5-$10 a gallon, takes 2 gallons of either one.
Miscellaneous hoses and fittings to adapt the flushing pump to the system, and the R134a adapter to the R12 gauge set = $15.

I did a R134a conversion on my 89GT, and used all stock parts. You will need to replace the dryer/receiver (about $75 if you get the one with the hose made as part of the unit), and should replace all of the rubber “O” ring seals as well. You will need to drain all of the oil out of the compressor and replace it with new R134a compatible oil. Next comes the nasty part – in order to get all the old oil out of the system, you will need to flush it with special flushing solvent, or mineral spirits (ok) or tetrachloroethylene (better, but may be hard to get). If you leave the old oil in place it will congeal and reduce the heat transfer in the condenser and evaporator (read that it won’t cool good) and possibly damage the compressor. As for the oil in the compressor, unbolt the compressor from its mounts, remove both fittings at the bolt on flange joint. Then turn the compressor upside down over a bucket and the oil will drain out. Pour a cup full of mineral spirits into the suction side (the side with the biggest hose) and swish it around, turn the compressor hub 5 turns, and dump out the mineral spirits. Set the compressor aside for 30 minutes or so that the mineral spirits can evaporate out. Then add 6-8 oz of r134a compatible oil to the suction port, swish it around while you turn the hub 10 turns so that the oil coats everything real good. Get the new O rings, coat them with oil, and replace the O rings at the flange joint you took apart. Re-install the compressor in the vehicle.

Connect the pump (I had an electric sump pump I bought for $20) to the hose from the high-pressure side of the compressor. Alternately, you could use compressed air to force the cleaning fluid through the system. I didn’t like to do this since compressed air has lots of moisture in it, which is death to A/C systems. Pump the cleaning fluid through the system and let it come out the hose that was attached to the old dryer/receiver. I used 2 gallons of mineral spirits and pumped it all through the condenser and evaporator. The expansion valve is located near the firewall in the high-pressure line of the evaporator, and may cause the cleaning fluid to trickle through the lines at a very slow pace. You may want to pump cleaning fluid through the evaporator and condenser separately to speed up the process.

Next comes the changing of all the old “O” rings so that the chances for leaks is minimized. Use the plastic connector tools to separate the lines, place the extended collar part of the tool so that it faces the large part of the connector and push inwards: this expands the spring so that you can pull the tube apart. You may need a helper to push on the tool while you pull on the tubes to separate them. Install the new “O” rings: be sure to coat them with new oil when you put them in. Install the new dryer/receiver, R134a service port adapter, connect the compressor, add about more 4oz of oil to high pressure line and tighten up all the lines. Close the hood, start the engine, let everything get hot under the hood, but don’t add the R134a or turn the A/C on. Connect the charging gauge hoses to the service ports on the A/C (red gauge = high pressure, blue gauge = low pressure) and open both valves, then connect the center hose to the vacuum pump. The purpose of this exercise is to heat up the system so that when you vacuum it all down (yes, you will need a vacuum pump- mine is an old refrigerator compressor), that all the air, vapor and moisture from the cleaning fluid vaporizes and is removed from the system. Vacuum it down for about 30 minutes, this should give you about 28” of vacuum or more inside the A/C system. I have a vacuum gauge “T” connected into the vacuum pump line so that I can accurately watch the vacuuming process. This is a good time to take a soda and sandwich break since it doesn’t go faster if you watch it.

Remove the electrical connector from the dryer/receiver and jumper the two connections inside the wiring harness side of the connector together: this allows the compressor to engage in spite of low pressure/no gas in the system. Close both charging gauge valves, and then disconnect the center hose of the charging gauges from the vacuum pump and connect it to the R134a can tapper. Put the R134a can in the can tapper and screw it down with the can tapper valve closed, then open the valve. Loosen the hose at the center connection of the charging gauge set until the R134a squirts out: this purges the line of air and moisture. The refrigerant is added through the low pressure side of the system, so open the low pressure gauge valve to add the R134a. As you add refrigerant, be sure to hold the can upright: this will insure that gas is added and not liquid. If you turn the can over so that liquid refrigerant is added, you may damage the compressor since gas compresses and liquid doesn't. Start the car and take note of the idle speed, then set the idle speed up to about 1200-1500 rpm, and turn the A/C on inside and set the fan speed on high. Watch for the pressure on the low side to drop off as you are filling, and the R134a can will get warm and stay warm. This tells you the current can is empty and needs to be changed for a fresh one. Before you disconnect the can, be sure to close the valve on the R134a can tapper.

Watch the high side pressure on the charging gages and regulate the adding of gas to keep the high side pressure under 350 psi. You will probably need a fan in front of the car to keep the readings below 350 psi. I had to put the R134a can in hot water while I was charging the system with it, or else the can got so cold that it quit flowing. Use caution when you do this so that you don’t get water in the charging adapter when you change the cans. When you have added the 2 cans of gas, the high side will read about 250-300 psi and low side about 28-38 psi. Turn the idle speed back to where it was, turn the A/C off, disconnect the charging gauges, and re-install all the caps on the service ports. Remove the jumper from the low pressure switch harness and plug it back on the switch connectors. Then put the R134a Service Sticker on, secure all the loose wiring on the system and you are done. I hope it cools good, mine doesn’t get quite as cold as it used to driving around town.

rockyracoon said:

thanx much for the info.BTW freeze 12 is readily available
on e-bay and it is my understanding that you can purchase it without any credentials whatsoever.supposedly it contains no CFSs and is not flammable.

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It seems that you are right about the Freeze 12, no license required. That's a change from when I got my EPA 609 certification. I hope that it works well for you.

You are on track with the nitrogen too check for leaks. Just use the low side as if you were charging it. If you want to flush the system with solvent remove the accumulator and disconnect the hoses from the commpressor. You don't want to flush either of the two. You can flush the compressor, but I would do it on at a bench and you flush it with new oil, not flushing solvent. Also don't flush the metal pipe with the orfice tube in it.

If I were you I would just use the nitrogen check it for leaks. It works, but not as well as dye, because some leaks are so slow time and dye will only show it.

Hope that helps.

I'm not a big fan of Freeze 12, unless it's composition has been significantly changed in the last 2 years.

I'm kind of bias on the whole R134 vs Freeze 12 debate, but here's my take on the matter. Freeze 12 does not cool any better or any worse then conventional R134. Here's why. Freeze 12 is 80% 134 and 20% 142 b. The 142 b is the gas in Freeze 12 designed to carry the mineral oil throughout your A/C system. The only advantage of Freeze 12 over R134 is that it's a great alternative for lazy people. Freeze 12 was made to sell to people that were too lazy to change out the mineral oil in their existing R12 System ( But even with Freeze 12 YOU STILL NEED TO CHANGE OUT the Accumulator with R134a compatable unit, replace all the Black O-rings with Green O-rings, and replace the hi level and low level hoses with Barrier Style hoses). When you convert to R134, you have to remove ALL the old mineral oil in the system (since it's not compatable with R134) and replace it with PAG or Ester oil. Since Freeze 12 is 80% R134a (which is not compatable with mineral oil), something is needed to carry the mineral oil. The 20% of 142b used in Freeze 12 carries the mineral oil in the system. But oil is important to the life of the compressor so why try to carry sufficient oil with only 20% of the refrigerant? The other thing to keep in mind is that 142 b has smaller molecules than R134. So if (or when) you develope a leak in a Freeze 12 system the 142 B is the first gas to leak out. Since 142 B is the gas that carries the oil in the system (and now you have none).....you have no oil circulating in the system which will lead to compressor lock-up over a very short period of time.
If it were me. I would do a straight R134 conversion and here's why. 1)Freeze 12 is 80% R134 anyway so why use a "blend" if you can go 100% R-134. 2) Sounds like your already planning on replacing your accumulator, hoses, O-rings, and compressor with R134 compatable units. If so, just flush out the condensor and evaporator to remove the remaining mineral oil and your system will now be ready for PAG oil which is R134 compatable. I'm not trying to sway you one way or another, but I just wanted to make everyone aware that Freeze-12 is not some type of miracle gas capable of R-12 cooling. It's a R134 gas which opperates on mineral oil assuming YOU HAVE NO LEAKS and none of the 142B leaks out. Good Luck with your decession.

Originally Posted by PuterAmI
Would you mind telling me why you think it is not safe?

A viable alternative to gasoline is an electric car or a bicycle or...

In other words, I am only trying to figure out if you mention it being flammable for some reason. I do not see it as a problem. I see it only as marketing hype.



Flammable refrigerants pose a significant danger to a vehicle’s occupants should a leak occur. A spark from a cigarette or a switch can/will ignite ANY leaking refrigerant causing an explosion and turning the vehicle’s interior into an inferno. All it takes is one little pinhole leak in a component such as the evaporator and boom......you won't know what hit you! It only takes about four ounces of a flammable hydrocarbon refrigerant such as propane or butane to create an explosive mixture inside a typical automobile passenger compartment. Would you ever consider running a liquid fuel pressure gauge in the cabin of your vehicle? If not, then why would you consider using a flammable refrigerant in your A/C system? In theory, they both represent the same risk.

Frontal collisions can also release the refrigerant if the condenser is damaged, which could result in a severe underhood fire causing extensive damage to the vehicle.

There’s also a risk to service technicians who might encounter leaks while servicing a vehicle or operating recovery/recycling equipment.

Just to clarify, my comment about a safer viable alternative for gasoline was directed at internal combustion engines. What is a safer, more viable, drop-in, alternative fuel for gasoline engines? My point being, anyone that chooses to use a flammable hydrocarbon in their A/C system does so at their own risk because there are more than enough drop-in replacment refrigerants on the market that do not pose a safety risk. The same can not be said for gasoline for those of us running internal combustion engines in our vehicles.

In my view, it comes down to risk vs. reward. Why would anyone want to risk the safety of themselves or their passengers by introducing a flammable substance into their A/C system if it's not necessary? Is the 3-to-4 degree temp. drop over R-134A worth it? If so, then why not spend the money and have the system refilled with R-12, which is perfectly safe and has a proven track record.

Just my two cents.....and I'll step down off my soap box

Very interesting. I Goolged but could not find any information on the composition of Freeze 12. I had heard that refrigerants that were blends like Freeze 12 were not the best choice because of the leakage problem as mentioned by 89 Saleen#455.

The other problem was that since it is a blend, you had to charge the refrigerant in a liquid state to keep it from separating. Charging it conventionally as a gas, it would be very easy to get an uneven blend. The two components have different boiling points, and so the gas in the cans doesn't boil off at an even rate. Therefore when you change cans, you may easily have more of the higher boiling point refrigerant left in the can. That upsets the blend ratio and the ability to cool & carry oil.

So funny how you guys says replace this and replace that to run 134... lmao... I........ put 134 in it............. and it blows cold as shiot........... for over a year now........ lol

I found the EPA info page on Freeze 12. The composition has not changed. Freeze 12 is still 80% R134A and 20% 142B. See this link.

http://www.epa.gov/Ozone/snap/refrigerants/macssubs.html

Scroll to very bottom of the alternative refridgerents. Number 9 (just casually thrown in the middle of the list) is "Freeze 12"

I just resent the marketing aspect of this product. The Snap company is really trying to lead people to believe that Freeze -12 (which is 80% 134a) is really a refined version of R12. Why not call it Freeze - 134/142b? Why use the number "12" in the product name when it contains absolutly ZERO R-12. It's extremely misleading and very disceptive. You wouldn't mind if it was Fruit Punch...ie Hawaiian Punch is not really from Hawaii or Kentucky Fried Chicken is not really from Kentucky. But we're dealing with a high pressure flamable gas for Gods sake. Just my $0.02

PoopDawg said:

So funny how you guys says replace this and replace that to run 134... lmao... I........ put 134 in it............. and it blows cold as shiot........... for over a year now........ lol

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You're a lucky guy. Did you flush the system before adding the "Death Kit"? The "Death Kit" ($24.00 conversion kit they sell on the self at Autozone) has been well documented on the adverse affects of Ford Compressors not designed to operate with R134a. Do a google search on "Ford, retrofit, A/C Compressor, Black Death".

http://www.aircondition.com/tech/qu...h??PHPSESSID=48f35f0cc3610ee7409b440cf8a8e8c2

When the compressor finally goes south....fragmenting into little pieces and contaminating your entire A/C system with black goo....it's going to be expensive.

Good luck in the meantime.
Who knows, maybe someone else swapped in a compatable R134a compressor? Is your compressor the stock FX-15 (stamped on the back)?

That info is good to know. I have heard of Freeze 12, but have not used it or heard of anyone using it. Thanks for the info.

89 Saleen#455 said:

Freeze 12 does not cool any better or any worse then conventional R134.

Click to expand...

http://www.ackits.com/testresults/alttest.pdf

Freeze-12 and R-134a show similar vent temperatures, but Freeze-12 gives much lower high side pressures. When you translate this to a Fox CCOT system, the Freeze-12 will outperform R-134a as our vehicles are condenser limited.