Dumb AC Recharge Question

[Yesterday617]

I'm asking this question here before I stupidly pose the questions(s) to my mechanic:

Have a 1990 325i
- Is it true that the AC can't just be 'recharged' without being changed to a whole new system?
- Is the old recharging stuff still available legally, but at a higher price?
- Any clue what either service would cost approx. (either new system or old stuff)?

 

[epj3]

I'm asking this question here before I stupidly pose the questions(s) to my mechanic:

Have a 1990 325i
- Is it true that the AC can't just be 'recharged' without being changed to a whole new system?
- Is the old recharging stuff still available legally, but at a higher price?
- Any clue what either service would cost approx. (either new system or old stuff)?

You can either find a garage who still has R12, and have them flush and fill it with that (Will be costly, $150+), or you can get the conversion kit which costs about $35 and contains about 40 seals, and have a garage flush and fill it with r134a for around $80. You MIGHT have to get a new compressor AND dryer to switch.

 

[jrt67ss350]

Eric is right. Alot of places will still recharge R12 systems with R12, but it's expensive. You can have the system converted to take R134 refrigerant which is cheap. You shouldn't need a new compressor provided yours is working ok, but you will need a new drier. Be aware that the R12 will work much better than R134. I've had both R12 and R134 in my '87, and the R12 is significantly colder. The compressors used in the e30s don't have very much output at low engine speed, so the system with R134 gets warm when sitting at stop lights in hot weather. E30s also have very small condensors which make matters worse.

It's a tough decision to make since R134 is much cheaper and available everywhere, but its performance in a system designed for R12 leaves much to be desired. If you decided to go the R134 route and you changed the seals yourself, it would then cost you about $40 or so to have an A/C shop evacuate and recharge the system with R134.

 

[epj3]

Eric is right. Alot of places will still recharge R12 systems with R12, but it's expensive. You can have the system converted to take R134 refrigerant which is cheap. You shouldn't need a new compressor provided yours is working ok, but you will need a new drier. Be aware that the R12 will work much better than R134. I've had both R12 and R134 in my '87, and the R12 is significantly colder. The compressors used in the e30s don't have very much output at low engine speed, so the system with R134 gets warm when sitting at stop lights in hot weather. E30s also have very small condensors which make matters worse.

It's a tough decision to make since R134 is much cheaper and available everywhere, but its performance in a system designed for R12 leaves much to be desired. If you decided to go the R134 route and you changed the seals yourself, it would then cost you about $40 or so to have an A/C shop evacuate and recharge the system with R134.

Justin - not completely true. R134a operates at different pressure, temperatures, and uses a different oil than the R12 system.

http://www.koalamotorsport.com/article-airconditioning.asp should answer most questions.

 

[jrt67ss350]

Yeah, I'm aware of all that. That doesn't mean you need a new compressor, though. The Nippondenso compressors work with R134, but they lack the low belt speed output that's needed for an R134 system to stay cold at idle. You do need to replace the drier when doing a conversion, however.

It's a simple fact that R134 does not work as well in a system that was designed for R12 - precisely because of the different refrigerant characteristics of the different molecule.

R134 systems can be nice and cold, but the system generally needs to either be designed for R134 or modified for this to be true. To achieve the same vent temps with R134 and R12 in the same car with everything being equal, the R134 system will require a higher output compressor, a condensor with a larger surface area, and higher airflow over the condensor.

 

[Big Daddy]

And remember that once all the R12 is gone, they are not making any more, it has been outlawed.

 

[dark_islight]

Use the freeze 12.

see www.freeze12.com for more info.

 

[UDPride]

If you are like me and want A/C to be ice cold when you need it, then stick with R12. Theres plenty of places that will still fill it up so I would not make availability a concern. In fact theres probably as many R12 cars on the road as R134A cars.

R12 in my experience does cool much better. For $40-50 more, why not just fill the car with the stuff it was made for and have your inside as cool as a cucumber.

My A/C cools pretty well until its about 85-87 degrees out. I had the car in the sun and on a 95 degree day and at full blast the A/C didnt do much on the inside at all. I think I need to get the R12 flushed and refilled. It probably hasnt been touched in 5-7yrs.

 

[epj3]

Use the freeze 12.

see www.freeze12.com for more info.

That's a BIG no-no. Why? Becuase if you use freeze-12, and take your car to a garage for any kind of servicing, it will more likely than not throw error codes on the mechanic's machines. Read the link I posted (i think they talk about it there). I would stay away from anything but r12 and r134a.

BTW if you're doing the r12 to r134 conversion and have a mechanic drain your system, make sure he pays you for the r12!! He can reuse that and if he doesn't pay YOU for the r12, then he's scamming you.

UDPride, my e34 did the EXACT same thing. Blew nice and cold till about 90 degrees with moderate humidity but then after that it got warm and didn't do anything unless you were on the highway for a while. I used up 3/4 of a can of R12 my dad had bought about 15 years ago to top off my system. Now it blows freezing cold alllllll the time. Makes me happy that's for sure.

 

[UDPride]

epj-

i may take car in and have the R12 topped off. I dont think it has a bad leak in it. Car didnt have much service for 5yrs before I bought it and it still blows pretty cold to about 85 degrees outside. If its hotter out than that though it just doesnt cut through the heat and seems to not blow as cold. I would think given the maintenance history of last 5-6yrs if it had a bad leak it wouldnt blow cold at all by now.

I'll let you know what happens if I get it topped off.

 

[jlh]

The prior posts all have good info but unless you are saavy with A/C basics and understand automotive A/C systems then you are best to go to a reputable auto A/C service center.
You mention that your system worked good untill you hit the mid 90's ambient and 50%+ RH. Well the weather that we had in the NE US end of July and early August pretty much exceeded system design. But if all is operating to spec the system may take awhile to pull down the interior but results should still be acceptable. That car has a lot of glass and that really degrades performance when the sun is shining. Shades or dark tint help.
A good A/C tech will be considering the ambient conditions while verifying with the guage set. The tech will not charge or top up a system based on bubbles in the drier site glass.
It is true that your system may be low on charge. The hoses will leak molecules and over time the system performance will degrade. A good sniffer check will note any leaks that need repair.
The only correct way to charge a system is reclaim, evacuate, leak check, and weigh in a charge.
Check the cooling fans and condenser coil. The electric fan operates when ever the A/C switch is lighted blue. It shifts to high speed on radiator water temp.
The engine driven fan must have a properly operating fan clutch. The A/C? depends on both fans to get proper airflow thru each heat exchanger (2) and remove the heat . Seeing both fans work is not good enough. The mechanical fan must be tached and verified that its speed increases propotionally with increase in engine RPM.
Make sure the condenser and radiator are clean and not blocked by dirt and bugs that impede air flow. The "my car doesen't overheat" or other similar quotes does not mean you have adequate flow for the refridgeration system.
Stay with R-12 untill you need to change a major component or blow a charge.

When the change to 134a comes, out with the Rcvr dryer, out with the expansion valve, out with the compressor, system flush both high and low sides, new dryer for 134a, you already have the TXV out so repalce it now or replace it later, flush the compressor on the bench with a quality ester "POE" oil stay away from PAG oils unless this is a compressor replacement and the comp is precharged with PAG.
This is the route or similar that a good A/C shop will recommend you take.

Bottom line - Find a good A/C shop and you'll do once.

Good luck