AC not getting any colder

[Eddie Haskell]

Here is one easy thing to check when you have the system open to atmospheric pressure. If the system has been charged without any knowledge of HVAC or just unknown. Most of the time the system will contain excess lubricant and leak detector dye if the DIYer hasn't charged with straight R134A. A quick check to set the lubricant level in the compressor is to remove the high pressure line from the condenser. Turn the engine/compressor over. This will blow out the excess lubricant from the compressor. Excess lubricant decreases system capacity and can flood the compressor. Place the high pressure line in a milk jug or such so that the lubricant doesn't spray everywhere. I realize that the manufacture will specify the proper lubricant for the system. To preclude compressor removal and the associate lines to evacuate excess lubricant this process works well and saves the toil of dis-assembly of a large part of the system. I also realize that if the system was overfilled with lubricant then some pooling in the condenser will occur. The only cure for that is to pull it, drain and clean excess.

[KI4UJO]

Both sides are interconnected. AFAIK you only have to pull vacuum on 1 port ("side") in the system, and the whole thing will go to the same vacuum equilibrium point.

Correct. When I did my 134a conversion, I only pulled a vacuum on the low side.

[CorvallisBMW]

Both sides are interconnected. AFAIK you only have to pull vacuum on 1 port ("side") in the system, and the whole thing will go to the same vacuum equilibrium point.

[91318is]

One more question. I was watching a few youtube videos and I noticed they vacuumed the high and low side. When I add freon, do I need to do anything special for the high side or can I just add freon to the low side? Sorry, haven't worked on an AC system before.

[91318is]

Ohh ok thank you guys. Sorry, wasn't reading very well. I am going to go ahead and get it vacuumed out soon. I will post results, sorry for the "stupidness" lol.

[pandaboo911]

Dude without a vacuum 10-20% of your refrigerant will be air, which doesn't refrigerate.
It's not expensive to do.

[LJ851]

Not sure what to vacuum. They were all brand new parts and everything was out of the car (including lines). The system works, it just won't get down to freezing temps like I see a lot of people posting with modded systems. I don't think a vacuum is really going to help my cause since the system runs fine, doesn't overheat the car, gets down to 50-60, and most parts were brand new when installed. However if a larger condenser fan doesn't do the trick, I will vacuum out the system as a last resort. A larger fan won't run much a wrecking yard.

Any time the system is opened for any reason it must be vacuumed before you add refrigerant. If it was optional, your system would be working well now which it is not.

I can't tell if you understand what is being told to you. This isn't vacuuming like you do to your carpet.

Pulling a vacuum on the air tight system removes all the air from the system and lowers the boiling point of the contaminants in the system so they will vaporize and can be removed under vacuum.

Any air or contaminants left in the system when you add refrigerant will greatly reduce the cooling capacity of the system. This is where you are, and precisely why you need to vacuum the system.

It's like eating a steak dinner without chewing. Yeah, you might get it all down but shit it doesn't work very well.

[91318is]

Not maybe, definitely.

It does not work without pulling a vacuum on the system before filling it with the correct amount of refrigerant.

Not sure what to vacuum. They were all brand new parts and everything was out of the car (including lines). The system works, it just won't get down to freezing temps like I see a lot of people posting with modded systems. I don't think a vacuum is really going to help my cause since the system runs fine, doesn't overheat the car, gets down to 50-60, and most parts were brand new when installed. However if a larger condenser fan doesn't do the trick, I will vacuum out the system as a last resort. A larger fan won't run much a wrecking yard.

[91318is]

Thanks Corvallis and Pandaboo. I was thinking the same thing. The previous owner had a different aux fan on the car and it is fairly small even compared to stock. I am going to be putting a faster/larger fan on the condenser and that should help a bit.

[pandaboo911]

1. Check for leaks with UV dye
2. evacuate and recharge
3. run aux fan on high speed instead of low speed
4. Profit / bob's ur uncle

[CorvallisBMW]

OK, stay with me here because this is going to get just a bit technical:

R12 has a higher boiling temperature than R134a. This is important.

The job of your condenser is to condense the pressurized vapor coming from the compressor back in to a pressurized liquid. Depending on how large or efficient your condenser is, it might be able to convert 100% of the vapor in to liquid, or maybe just 50%. Since R134a has a lower boiling point than R12, the condenser's job becomes more difficult. As an example, let's say the condenser is sized by the mfr to get R12 vapor from 80C to 40C (at a given pressure) in order to condense it fully. Now with R134a, it has to get it from 80C to 30C because R134a boils at a lower temp. This is a 25% larger delta (difference), meaning the condenser has to do 25% more work. It's therefor not able to convert 100% of the vapor in to liquid. When the now vapor/liquid mix hits the expansion valve, the portion of the mix that is liquid flashes to vapor and cools, but the portion that was still vapor does not, meaning less overall cooling effect.

Essentially any time you convert from R12 to R134a, your condenser becomes undersized. It's not because of anything you did/didn't do, it just is. There's also the fact that R134a has a lower specific heat (less ability to hold energy, i.e. cool) than R12, so it is less efficient. Most R134a systems are 20-30% larger in both component size and volume than a comparable R12 system to account for this loss in efficiency.

The #1 thing you can do when converting to R134a is to do it properly (which it sounds like you have with all new parts) and to make sure the system is fully evacuated before filling (which has already been mentioned). If there's any air in the system as you fill it with R134a, that air will take the place of what could have been refrigerant, and will further hurt the system efficiency (air also contains moisture which also hurts efficiency). Hence why it's important to take the system in to a vacuum and then fill it with R134a, so that you get the maximum amount of pure refrigerant possible in to the system and not a mixture of air/R134a.

Long winded I know, but sometimes it helps to understand the mechanics behind it :)

[LJ851]

I didn't have the system vacuumed but the evaporator, all the lines, expansion valve, condenser, compressor, and drier were all out. Maybe I should have vacuumed the system anyways.

Not maybe, definitely.

It does not work without pulling a vacuum on the system before filling it with the correct amount of refrigerant.

[steve68]

yes!!!!^^^^^^

[91318is]

@Klug Sorry one more thing, I didn't have the system vacuumed but the evaporator, all the lines, expansion valve, condenser, compressor, and drier were all out. Maybe I should have vacuumed the system anyways.

[91318is]

I spent around $250 as well. Including the condenser, valve, drier, seals, used/tested evap, R134A and PAG. Wasn't too bad. At highway speeds it keeps me from sweating, just not that cold blast you should get when you start the car and at idle.

@klug, I will have to check out the high pressure reading. My low is about 40psi and for some odd reason I cannot get anymore into the system.

My secondary belief is my condenser fan. The previous owner had a odd one in there that seems fairly small and it is about 1 inch from the condenser itself. I am thinking of getting a 90's 750i fan seeing that they have worked for other people. Only issue I have now is my bumper won't come off!

Thank you for all the replies. I will try to upload some photos/more info soon.