Car A/C pros, need a little help

[Jason280]

The A/C on my '91 Mazda B2600i has not been cooling as well as it should, and I am pretty sure its simply low on freon. The compressor is slow to switch on at times, and in the past I have used the store kits to recharge the system. Instead of continuing to use the 16oz kits, I went ahead and invested in a set of gauges and a 30lb tanks of R134.

I've always wanted to learn how to do A/C work, so I figured this would be a good experience. Here's what I have so far:

Do I have everything I need to recharge the system? I know ideally it would be best to find the slow leak and repair, but this will suffice for now. I do plan on eventually picking up a vacuum pump, but for right now, I would like to at least be able to recharge the system.

How do I need to proceed? Any good tutorials online? Thanks!

 

[jayoldschool]

First up, are you sure that 91 is R134a? Many cars were still R12 back then. Second, if it's low, it has a leak.

 

[Jason280]

Yes, it was converted to R134 several years ago. As far as the leak goes, its a sloooooow leak, so I am not too concerned with it at this time. Sure, it needs to be addressed, but at this point I do not have a vacuum to use (so I will simply be topping off the system).

 

[Falcon67]

Which is bogus - your system is probably contaminated with air and moisture, so a "top off" is worthless. You need to go buy a vacuum pump, evac the system and pull a strong vacuum on it for a couple of hours. Then seal it up, test that it holds the vacuum, then fill. you got two out of three tools - you need all three to do a proper job.

 

[pop pop]

You seem to have a few of the tools, but not all, and only a smidgen of the knowledge. If what you propose works, why do AC shops survive? It just isn't that simple when you know what you are doing. See a pro before you hurt yourself or cost yourself more $.

 

[RKA]

Which is bogus - your system is probably contaminated with air and moisture, so a "top off" is worthless. You need to go buy a vacuum pump, evac the system and pull a strong vacuum on it for a couple of hours. Then seal it up, test that it holds the vacuum, then fill. you got two out of three tools - you need all three to do a proper job.

So let's say his AC has always worked and still continues to work, just not as well. Can we then assume there is and always has been refrigerant in the system? Is the refrigerant inside the system at greater pressure than atmospheric? If so, is it reasonable to believe that air (and hence moisture) hasn't contaminated the system? If moisture is in the system, aside from compromising the life of the compressor when mixed with the oil in the system, what are the other drawbacks? Since the car question is over 20 years old, perhaps the OP might decide that those are non-issues.

 

[Jason280]

The air still blows cool at the lower fan speeds, but not as cool as it has in the past. I need to pick up a thermometer to get an exact reading, but its definitely cooler than simply running the vent.

I hooked up the gauge set, and here are the readings:
Low Side - 75 psi
High Side - 75 psi

This was with the truck idling, and the fan set to speed "3" with the A/C running. Now, if I hook it up to one of the Advance Auto DIY kits, it simply reads "low". I'm not against buying a vacuum pump, but I am curious if I couldn't simply top off the charge and see how well it cools. I certainly have plenty of freon, just lack the necessary knowledge at this time.

 

[Falcon67]

If barrier hose was not used in the conversion from R-12 to 134, then that will be one of your problems. You can keep dumping in charge and it may work for a while but it will be less and less effective. Air contaminates the charge and greatly reduces the system efficiency. The refrigerant doesn't just leak out, something goes in to take it's place. It's supposed to be sealed and when the system isn't that's when problems start. 2 years old or 20 years old - the system is designed to be sealed in order to work right and the materials used in the system have to be compatible with the refrigerant. It may limp along, but it isn't right. Contamination hurts the dryer and may damage the compressor and/or the expansion valve (or orifice tube). If the compressor or the vanes inside let go, you'll be tossing everything expensive, flushing for hours and replacing expensive parts.

Your working pressures noted are way low. Low side usually mirrors - to some extent - the evap temp. High side depends on charge and ambient. Careful - a little too much 134 and you could end up with 300+ psi in your face. There are some good books on the subject, so learning how to isn't a big issue.

 

[38Chevy454]

The air still blows cool at the lower fan speeds, but not as cool as it has in the past. I need to pick up a thermometer to get an exact reading, but its definitely cooler than simply running the vent.

I hooked up the gauge set, and here are the readings:
Low Side - 75 psi
High Side - 75 psi

This was with the truck idling, and the fan set to speed "3" with the A/C running. Now, if I hook it up to one of the Advance Auto DIY kits, it simply reads "low". I'm not against buying a vacuum pump, but I am curious if I couldn't simply top off the charge and see how well it cools. I certainly have plenty of freon, just lack the necessary knowledge at this time.

You need to close the valves on the gages. You are getting bleed through so that both gages read the same. Must be separated and that is doen by the valves at each end of your gages. Your normal low should be around 30 psi and high around 200-300 depending on outside temp.

I suggest you just read up and learn. It is not really that hard, I am basically self taught, and i am sure that I do not always do everything textbook correct Having a vacuum pump is a critical tool for doing A/C work. You might be able to just top off your system and have it work. Depends on how much contaminants (meaning non-refrigerant) in your system. Any moisture or air will only bring down the efficiency.

 

[Iroc-Z]

That is not always true. Equal pressures could be a compressor problem also. I have seen that before.

Also things needed to perform a/c work properly.
Gauge Set
Scale
Vacuum Pump
Good quality a/c dye

Honestly you will not get really good results with skipping steps. I was lucky enough to pick up a used robinair a/c machine off of craigslist for 200 bucks. But getting the moisture out is key.

 

[slice]

please tell me how contaminates got in with Freon. The system has pressure on it. Which pushes out not ***** in. If it low add some. You have all you need. Hook up blue connector to suction line. It only fits on suction line. Purge gauges of air by pressuring up with Freon. Turn on system make sure compressor is turning and add Freon slowly when cold stop flow disconnects and cap.

 

[Iroc-Z]

Because when you have a leak and the system goes empty moisture gets into the system. Moisture will screw with pressures and cause the system not to work right. Also I bet the drier in that system is original and does not absorb moisture anymore.

 

[pop pop]

please tell me how contaminates got in with Freon. The system has pressure on it. Which pushes out not ***** in. If it low add some. You have all you need. Hook up blue connector to suction line. It only fits on suction line. Purge gauges of air by pressuring up with Freon. Turn on system make sure compressor is turning and add Freon slowly when cold stop flow disconnects and cap.

Yep, it's just that simple.

 

[493 scamp]

Vacuum pump from Harbor Freight for cheap,also oil will leak out with the front. You need away to add oil,we vacuum system and let vac pull in oil on the low side. We have been using Ester oil with dye in all systems for many years now with no failures retrofitted or not,only exception is Hybrid cars with electric pumps they need special non conductive oil. You can make an oil adding hose out of your old can adapter. Getting the correct charge in the system is the hard part due to the retrofitting,you can get close if you are careful by watching pressures. Make sure your fan is pulling good air through the condenser too.

 

[nehog]

Yes, it was converted to R134 several years ago. As far as the leak goes, its a sloooooow leak, so I am not too concerned with it at this time. Sure, it needs to be addressed, but at this point I do not have a vacuum to use (so I will simply be topping off the system).

1. Converted? OK, that's why it doesn't work nearly as well as it did before the conversion. Don't expect R-12 cooling when converting to R-134a.

2. This is not like adding oil to your engine. You cannot top off, you must evacuate, and refill, sometimes it is necessary to replace the drier as well (if the system was totally at 'zero' then the drier replacement is a good idea...)

 

[38Chevy454]

please tell me how contaminates got in with Freon. The system has pressure on it. Which pushes out not ***** in. If it low add some. You have all you need. Hook up blue connector to suction line. It only fits on suction line. Purge gauges of air by pressuring up with Freon. Turn on system make sure compressor is turning and add Freon slowly when cold stop flow disconnects and cap.

If you do not purge the lines you can induce air, many of the cheap "top off" kits sold people just hook up and then charge away. This can allow air into the system. If the system was open for any length of time it will have moisture. If it was never opened, then pressure inside will keep moisture chances low. But air circulating around a closed A/C system does nothing for cooling and only makes the system work harder for no benefit of cool air coming out the vents.

It really is best to vacuum the lines and then charge as there will be essentially no chance for air. Purging them a small amount will get rid of most of the air and is good practice. Just don't tell the EPA

 

[JCQuick]

in the past i have always had friends very knowledgeable on a/c take care of all my needs. The last few years that has not been the case so I had to learn myself and mind you all those friends always let me help and expailed things plus being in the automotive biz 30 plus years doesn't hurt. Anyway as others have said you need to vacuume the system and fix the leak to do it right.
I just had to do compressor replacements on my wifes tahoe and my chevy truck and i'm still learning

 

[Iroc-Z]

Vacuum pump from Harbor Freight for cheap,also oil will leak out with the front. You need away to add oil,we vacuum system and let vac pull in oil on the low side. We have been using Ester oil with dye in all systems for many years now with no failures retrofitted or not,only exception is Hybrid cars with electric pumps they need special non conductive oil. You can make an oil adding hose out of your old can adapter. Getting the correct charge in the system is the hard part due to the retrofitting,you can get close if you are careful by watching pressures. Make sure your fan is pulling good air through the condenser too.

That dye in ester oil is worthless. I switched to this stuff http://www.tracerline.com/node/366 Can find leaks right away. You can see them with a dye light and not even need glasses.

 

[Iroc-Z]

in the past i have always had friends very knowledgeable on a/c take care of all my needs. The last few years that has not been the case so I had to learn myself and mind you all those friends always let me help and expailed things plus being in the automotive biz 30 plus years doesn't hurt. Anyway as others have said you need to vacuume the system and fix the leak to do it right.
I just had to do compressor replacements on my wifes tahoe and my chevy truck and i'm still learning

Thats just it. Honestly if I did not work at a shop and have a/c equipment to do it right I would pay an a/c shop to do the evac and recharge the proper way. The system will work way better.

 

[JCQuick]

Thats just it. Honestly if I did not work at a shop and have a/c equipment to do it right I would pay an a/c shop to do the evac and recharge the proper way. The system will work way better.

I agree I still have some connections its just not as convenant anymore and during my learning curve the amount of 134a i wasted would have covered the bill. But I'm proud to say that both are working very well at this time.

 

[chris142]

Has the dryer been changed? It should be if it's the old R12 dryer as the R134a will eat the bag in side it and then it will completly contaminate the system with dessicant.

Was 3.5oz of Ester oil per lb of R134a added?

High side pressures "should" be 2.2-2.5 Ambient temp with the engine running 1800 rpm and with a working fan clutch.

So say it's 90F outside. High side should be 198-225 and the low side line should be cold all the way back to the compresser.

As already said. The proper repair is to evacuate the existing Refrigerant, find and repair the leak, add oil,vacuum and charge.

 

[mellamoesrico]

There's usually a low pressure switch on the suction side and a high pressure switch on the discharge side of the compressor that interlock (prevent) the magnetic clutch from engaging when the pressures are outside of safe limits. If your pressure gets below the setting of the low pressure switch (which will happen when you evacuate the system or have a big leak), then you might need to bypass (jump out) the LP switch to engage the compressor clutch, in order to re-fill it with freon.

Reason is that when the compressor isn't turning, the suction and discharge pressures equalize somewhere in the between the normal suction and discharge pressures (say 150 psi). You refill the freon into the suction side, but the refill bottle's vapor pressure can't buck this much pressure. Once you get the compressor turning, the suction pressure gets pulled down to a lower pressure (normally about 30 psi) that your refill bottle can overcome, and opening your fill valve on the manifold will now allow freon to flow into the suction side.

Don't run it for long with the LP switch bypassed, just long enough to get refilled. Then put the switch back in service. And never jump out (bypass) the HP switch.

You need to search the internet for a chart that shows discharge pressure vs ambient temperature for your type of freon. This will tell you what your HP side should be for your local ambient temperature while the recharge is being done. NOTE, the chart assumes that you have adequate airflow over the condensor coil to remove all the heat the compressor is delivering to it. If you aren't providing adequate airflow, then you will recharge the system under heat soaked conditions; and some of the pressure you are reading is due solely to the high temp in the condesnor coil. As soon as you get the car moving and get some real amount of airflow over the condensor coil, the freon will "shrink" as the condensor coil cools off, and the pressures will go down below what you were reading on the manifold gauges under heat soaked condition.

So hopefully while recharging the unit, you can put a large shop fan blowing air into the front of the car's grille, to help get rid of the heat at the condensor coil (the one spooning with the radiator). If you just rely on the car's electric cooling fan, it can't remove enough heat from the condensor coil. This heat soaking causes the pressures to climb higher than they would be under normal conditions, and when you charge to the HP pressure listed on the chart, you won't really be putting in as much freon as you should.

Hope this helps.

 

[JamieK]

Is the compressor even working? Hook up the guage set. Note the readings (should be 60-80 psi). Crank the car, and turn the air on. Is the a/c clutch turning? If it is, then note the readings. If they are still the same as before, then you have an internal compressor failure.

 

[gpalmer77]

I used to be part of the top up camp, got fed up with crappy A/C though and converted to being smart, and bought the right tools.

I just replaced a bad condenser on my 5 series, replaced the dryer while I was in there. Pulled vacuum overnight, then charged the system with a little oil, and the exact amount for freon. Now my knuckles go numb it blows so cold.

Listen to the guys telling you that topping up is not the best way to go. It might blow colder, but it is not going to blow as cold as it should.

If it needs a top up, it is leaking, and it isn't gonna heal.

 

[KinzeMech]

This http://www.amazon.com/dp/1563923815/?tag=atomicindus08-20 is a good book. Get it, and read it cover to cover, and you will understand the fundamentals.

There's a lot of useful information on the internet. There's also a lot of useless information on it, and it is tough to know the difference. If you get a good book, you will begin to be able to separate the good information from the bad

There's a lot of bad information in this thread alone.

Barrier hoses are not that big of a deal. A new non barrier hose would probably leak a few ounces per year, but a used one usually will not. The mineral oil used with R12 soaks into the hose and makes it less permeable. If you have the means to top off refrigerant, I'd do that sooner than replace a hose that leaks a few ounces a year on a 20 year old car.

Someone said you cannot top off the system, that you must pull it down and recharge. That is absolutely, totally false. With some blended refrigerants that is true, but not with r134a.

Someone said you need a vacuum pump and need to pull vac on your system. This is a necessary if you have opened any part of the system. If you have not opened the refrigeration system, then pulling a vacuum is not necessary. It may be recommended if the system has been completely flat (0psi), but it is not absolutely necessary. If the system has been low, but has never been completely flat, pulling a vac and recharging would be wasting time (unless necessitated by opening the system to perform a repair.)

It's a 20-21 year old vehicle. At that level of age, you have to decide if it is worth the textbook proper repair, or not. It is common to see leaking shaft seals in vehicles that age. A common symptom of a very slight leak at the shaft seal is if the system leaks, but only when the ac goes unused for longer periods of time. A slight leak will seal up when the seal is lubricated by refrigerant oil during use. You have to use your judgment if you want to fix this problem, or keep replacing refrigerant.

If it is a shaft seal leak, it will only get worse. I had a car that had a leaky shaft seal, and I used it for 5 years like that. Every spring I had to put 2 cans of refrigerant in it. As long as the AC was used at least once every 2 weeks, it never lost any performance, if it went a month without use, it would all leak out.


Regarding the pressures you posted earlier, are you certain the compressor was operating? Equal pressures indicates either compressor not operating, catastrophic compressor failure, or incorrect usage of your gauge set.

 

[cj7365]

Here is a great A/C forum, these guys are very helpful, plus they have a shop in AZ


http://www.autoacforum.com/

 

[Jason280]

Thanks for the information. Looks like it would be best for me to simply drop the coin on a vacuum pump.

Any reason I should avoid either of these pumps?

http://www.harborfreight.com/25-cfm-vacuum-pump-98076.html

http://www.harborfreight.com/two-stage-3-cfm-air-vacuum-pump-66466.html

 

[KinzeMech]

Haven't used them, so I can't say, but if you get one of them, find a 20% off coupon before you go.

 

[38Chevy454]

Thanks for the information. Looks like it would be best for me to simply drop the coin on a vacuum pump.

Any reason I should avoid either of these pumps?

http://www.harborfreight.com/25-cfm-vacuum-pump-98076.html

http://www.harborfreight.com/two-stage-3-cfm-air-vacuum-pump-66466.html

Either one should be fine for occasional home use. They may not **** down to as low of vacuum as a real good pump, but it will be fine for your purposes. The low vacuum just helps to get as much moisture out as possible. Make sure the car is warm and those will have plenty of vacuum level.

There was a thread on here with A/C discussion, one of the members listed a website that had a manual he wrote. Very good info and you should try to find it.

 

[RKA]

Someone said you cannot top off the system, that you must pull it down and recharge. That is absolutely, totally false. With some blended refrigerants that is true, but not with r134a.

Excellent info! Can you please elaborate on the quote above? Specifically why blended refrigerants would require reclamation, vacuum and recharge when you have a leak? I thought as long as there is pressure in the system outside air and moisture couldn't get in, so I don't understand what's going on with blended refrigerants that's different. TIA!

 

[Tarheelgarage]

While I am normally in the camp that says to recover, fix/repair leak, pull deep vac, then charge; on this older vehicle, I would probably just shoot some 'gas and monitor vent temp gages to get it into approximate range.

Remember, this was orginally an R12 system, so there was some approximation (80-85%) done on the R134 charge when it was retrofitted.


Or you could go hog wild, rip everything out and install a brand spanking new system for about $2,000....

 

[KinzeMech]

Excellent info! Can you please elaborate on the quote above? Specifically why blended refrigerants would require reclamation, vacuum and recharge when you have a leak? I thought as long as there is pressure in the system outside air and moisture couldn't get in, so I don't understand what's going on with blended refrigerants that's different. TIA!

R12, and R134a are unblended refrigerants. They have a uniform chemical composition. R12 is dichlorodifluoromethane, and R134a is tetrafluoroethane.

Blended refrigerants are mixtures of different chemicals. When a blended refrigerant system has a leak, it is possible for the different components of the mixture to leak at different rates. This causes the proportions of the blend to change, which changes the refrigeration characteristics of the blend, which alters the performance of the system, typically causing it to cool worse, or not at all. Topping off a fractionated system like that brings the blend closer to (but not all the way) back to normal.

Blended refrigerants are a pain in the ***.

 

[Carguy99]

http://www.garagejournal.com/forum/showthread.php?t=152949

here try this thread

 

[Carguy99]

Blended gases react like a single gas in a closed system. However if they become unblended they react like individual gasses. these blended gasses are combined under specific pressures and temps. The problem occurs because of the different size molecules smaller ones leak sooner. this " unblends the gas."
way too much info here
http://en.wikipedia.org/wiki/Dalton's_law
Basically what happens is once it becomes unblended then 15 psi of gas X and 20 psi of gas Z becomes 45 psi of closed system pressure. this is the same process that occurs with contaminants in the system. (Air) Even small amounts can increase head pressures and limit cooling.
these blends are EPA certified for flammability and ozone depleting gases however, they are not tested for performance in an AC system.
IMO, I would never use them.

 

[RKA]

Interesting...learn something everyday around here! Thanks guys!

 

[stingry]

This http://www.amazon.com/dp/1563923815/?tag=atomicindus08-20 is a good book. Get it, and read it cover to cover, and you will understand the fundamentals.

There's a lot of useful information on the internet. There's also a lot of useless information on it, and it is tough to know the difference. If you get a good book, you will begin to be able to separate the good information from the bad

There's a lot of bad information in this thread alone.

Barrier hoses are not that big of a deal. A new non barrier hose would probably leak a few ounces per year, but a used one usually will not. The mineral oil used with R12 soaks into the hose and makes it less permeable. If you have the means to top off refrigerant, I'd do that sooner than replace a hose that leaks a few ounces a year on a 20 year old car.Someone said you cannot top off the system, that you must pull it down and recharge. That is absolutely, totally false. With some blended refrigerants that is true, but not with r134a.

Someone said you need a vacuum pump and need to pull vac on your system. This is a necessary if you have opened any part of the system. If you have not opened the refrigeration system, then pulling a vacuum is not necessary. It may be recommended if the system has been completely flat (0psi), but it is not absolutely necessary. If the system has been low, but has never been completely flat, pulling a vac and recharging would be wasting time (unless necessitated by opening the system to perform a repair.)

It's a 20-21 year old vehicle. At that level of age, you have to decide if it is worth the textbook proper repair, or not. It is common to see leaking shaft seals in vehicles that age. A common symptom of a very slight leak at the shaft seal is if the system leaks, but only when the ac goes unused for longer periods of time. A slight leak will seal up when the seal is lubricated by refrigerant oil during use. You have to use your judgment if you want to fix this problem, or keep replacing refrigerant.

If it is a shaft seal leak, it will only get worse. I had a car that had a leaky shaft seal, and I used it for 5 years like that. Every spring I had to put 2 cans of refrigerant in it. As long as the AC was used at least once every 2 weeks, it never lost any performance, if it went a month without use, it would all leak out.


Regarding the pressures you posted earlier, are you certain the compressor was operating? Equal pressures indicates either compressor not operating, catastrophic compressor failure, or incorrect usage of your gauge set.

FINALLY!!! SOME GOOD ADVICE. This guy is right on!

 

[Jason280]

Regarding the pressures you posted earlier, are you certain the compressor was operating? Equal pressures indicates either compressor not operating, catastrophic compressor failure, or incorrect usage of your gauge set.

Honestly, I am not sure. Its possible the compressor hadn't kicked on when I hooked up the gauges, so it may be beneficial to retest. I've noticed that the compressor is sometimes hesitant to "turn on" if I crank the truck with the A/C switched on in the cab. However, I can usually turn it off and back on, and the compressor will kick on.

As mentioned, it is a 20+ year old vehicle and I don't want to drop a lot of money into trying to fix this issue. I don't mind buying the necessary equipment, as I would like to learn how to do this kind of work myself. I certainly don't want to pay someone else to do it, as this becomes cost prohibitive. Last I checked, vacuuming out a system and recharging was at least $100-200, which would easily buy my own vacuum pump and a few other tools.

Here's a question I haven't been able to find the answer to, and it regards using the 30lb tank. Is it possible to "top off" the system using the 30lb bottle and gauge set, or will I need a vacuum pump or other equipment? I understand that R134a needs to be pretty close to the manufacturer's specs for refrigerant amount, but there is no way for me to know exactly how much is in the lines at this time. At this point, there's really nothing for me to lose with trying a top off the lines, assuming I don't overcharge. Can I simply use a thermometer in the vents and add R134 until it cools to a proper level, assuming I have a fully functioning A/C system (that is simply low on charge)? I always have the option of buying one of the 16oz cans and using the store bought kit I already have, but I don't really like the idea of buying more refrigerant when I currently have 30lbs sitting unused in the shop.

Thanks!

 

[KinzeMech]

What is in the "store bought kit"? Usually they have refrigerant cans with "special magic additives". Leak sealer, performance enhancer, whatever. It doesn't matter, they're all junk, and best avoided (except UV dye additive. that stuff really works). I would do without AC on a hot July day before I would charge one of my systems with that junk.


You can top off just fine from a 30# tank. There is nothing wrong with charging by pressure/performance. The difficult part of doing it that way is the fact that charging by pressure/performance is something that gets much easier to do well with experience.

Come back with the following information:
Air on recirculating, blower on MAX, engine idling, thermometer in center vents.
Allow the system to run 5 or 10 minutes to reach a stable condition.

Is the compressor running? Continuously, or cycling on/off? If cycling, what frequency?

Temperature at center vent?
Low side pressure?
High side pressure?
Ambient air temperature and conditions?
Grab the suction (return) line with your hand. It should feel cold, and under most conditions should actually be sweating.

I have more information to post, but need to go to work now...

 

[pop pop]

Honestly, I am not sure. Its possible the compressor hadn't kicked on when I hooked up the gauges, so it may be beneficial to retest. I've noticed that the compressor is sometimes hesitant to "turn on" if I crank the truck with the A/C switched on in the cab. However, I can usually turn it off and back on, and the compressor will kick on.

As mentioned, it is a 20+ year old vehicle and I don't want to drop a lot of money into trying to fix this issue. I don't mind buying the necessary equipment, as I would like to learn how to do this kind of work myself. I certainly don't want to pay someone else to do it, as this becomes cost prohibitive. Last I checked, vacuuming out a system and recharging was at least $100-200, which would easily buy my own vacuum pump and a few other tools.

Here's a question I haven't been able to find the answer to, and it regards using the 30lb tank. Is it possible to "top off" the system using the 30lb bottle and gauge set, or will I need a vacuum pump or other equipment? I understand that R134a needs to be pretty close to the manufacturer's specs for refrigerant amount, but there is no way for me to know exactly how much is in the lines at this time. At this point, there's really nothing for me to lose with trying a top off the lines, assuming I don't overcharge. Can I simply use a thermometer in the vents and add R134 until it cools to a proper level, assuming I have a fully functioning A/C system (that is simply low on charge)? I always have the option of buying one of the 16oz cans and using the store bought kit I already have, but I don't really like the idea of buying more refrigerant when I currently have 30lbs sitting unused in the shop.

Thanks!

There is definately a lot more you can loose at this point. It's what you don't know that is obvious. You need help, not equipment. You could blind yourself screwing around with somthing like this you don't have an understanding of. But good luck, cause you aren't listening.

 

[Jason280]

You could blind yourself screwing around with somthing like this you don't have an understanding of. But good luck, cause you aren't listening.

Not sure what you're issue is, but the whole reason I posted this thread is to learn from those familiar with A/C systems. Yes, I fully understand that the system is pressurized, and I fully understand that there is a certain amount of danger inherent in repairing such a system. That doesn't mean, however, that I am not both capable and careful enough to correctly learn what is necessary. A/C work isn't some mystical mystery that only a few can grasp, and I have little doubt in my abilities to figure it out with some assistance.

That being said, I do appreciate your concern...

Air on recirculating, blower on MAX, engine idling, thermometer in center vents.
Allow the system to run 5 or 10 minutes to reach a stable condition.

Is the compressor running? Continuously, or cycling on/off? If cycling, what frequency?

Temperature at center vent?
Low side pressure?
High side pressure?
Ambient air temperature and conditions?
Grab the suction (return) line with your hand. It should feel cold, and under most conditions should actually be sweating.

I picked up a vent thermometer, so I'll get the information as soon as I get a chance to mess around with the truck. I spent the better part of the morning pulling a set of seats to swap out in my Jeep, so I didn't get a chance to do much with the Mazda.