Set To Recharge AC, Help With Facts
 

Hey guys, gals,

I am getting set to replace the Schrader valves on my X5 AC system and just want to offer a little obtained knowledge and do a little fact checking before I do the work.

The AC guy I have been working with claims that the majority of problems on AC systems are leaking Schrader valves. He did my little Fiero project car because of this and now the AC runs like a champ. My X5 also has a non-op AC system and when I pulled the cap off the high pressure side valve, it was hissing. Now there is an o-ring in the cap itself but this will leak in very small amounts until the freon level drops below the low pressure safety switch threshold and that stops the system from working. There can still be pressure in the system, just not enough to operate above the switch.

For those of you who have cold air on drivers side and war on the passenger side, this I have learned is the way BMW designed the system to work. When the pressure starts to drop due to a leak, the passenger side will stop blowing cold first.

I also discovered that my particular MY, X5 uses a different type of Schrader valve and found the normal ones for it on eBay. Parts should be here today. What I started with was unscrewing the cap on the high side a little until I heard hissing. I did this to allow the 134 to vent out since the next step is to remove the current Schrader valves and replace them with the new ones on order. I also wanted to drain it slowly as to not lose any compressor oil. Hopefully that works out.

Here are my questions:
The lowside Schrader valve is the one closest to the firewall correct? This is where I will recharge from. My new schraders have colored caps so I assume the red cap is for high side and the blue cap is for lowside?

I have read the system holds 1lb of refrigerant. How is this determined on the cans of 134 you buy from the shop? I have only seen pressure readings on these cans with no way to determine for sure how much by volume has been added. Are the supplied gauges on the cans trustworthy? I have seen that 45 psi is supposed to be the range you want to be in. I won't have gauges to check both pressures high and low so I just want to know how much faith I can have in these cans for an accurate refill.

Cheers
Bernie

You will weight the can of refrigerant and as you charge the system you will continue to weight the can of refrigerant until 1 lb. has been removed. Most shops don't use the small cans of refrigerant but buy them in bulk size so they just put the container on a digital scale and watch the scale until 1 lb of gas is removed from the container.

Before adding refrigerant to the system you should determine if the system is low to begin with. What are the high side and low side readings? What is the static pressure if the compressor is not engaging. Does the compressor engage?

I had a bad condenser fan which the DME was able to log a fault code and if the aux fan is bad, I don't think the DME will enable the compressor to engage. Replaced the aux fan and my ac is working fine, whereas before the compressor wouldn't engage.

Before blaming low refrigerant, get the truck scan to determine it's not something else that causing the ac not to cool. Pressing the shraeder valve on the low side is not a valid test for determing the amount of refrigerant in the system.

The Schrader valve on the high side was definitely leaking.
Too late to check current levels as I already evacuated the 134 so I could change them out.

The truck throws no codes at all currently. I know because I had a check engine light a few weeks ago and it threw a code for that. Fixed as it was a bad oxygen sensor.

Having an issue now that I need help with though. I went and got a can of refridgerant a little while ago. New Schrader valves are installed and I started to fill the system on the low side. The gauge on the can started reading 45psi only seconds after I started to fill it. There is hardly any 134 in the system but the reading remains at 45psi?

I am assuming this is because the system is not currently running as there is absolutely no 134 in it. Do I need to somehow make the system run to accept the refrigerant? If I am supposed to, how do I do this?

The truck was running and the AC controls were all set to maximum. If what I have learned is correct that the system won't operate with too low a pressure, I am thinking I need to somehow get that system running so it pulls the 134 through?

Bernie

Yes, it has to be running. Sometime you can force enough juice in there to trip the pressure switch, sometimes you need to jump it. But, if you've opened your system, like you say you have, you really should have a shop do the recharge, they need to draw a vacuum to suck all the air out while putting 134 in.

Yes,

I just read up on that.
I have a friend that has the tools needed to do it but was trying to save myself a trip across town to get it done.
No big deal, he can pull vacuum on the system and get the 134 in there I am sure.
Good to know.

Thanx!

Bernie

Careful with jumping the compressor, unlike past ac systems, the ac system in our X gets the signal from the DME to turn on the compressor. You can fried the DME if you don't know what you are doing.

Actually if you don't know anything about servicing ac system you shouldn't be doing it and from your postings it doesn't appears that you have a clue as to how to service the ac system.

Nobody, including you has a clue how to do anything until you figure out how to do it. I can make sense of things pretty quickly and understand now what is needed to get the system to take the refrigerant. My friend will handle it from here as he has all the necessary tools. I will busy myself building roadracing engines.


Thanks for the info and of course the vote of confidence.

I was lucky in that I was taught by an ASE certified mechanic on how to repair cars and how to service ac system, and who also happens to be my father. I did not learn by trial and error which is what it seems like you are doing.

As for the vote of confidence all I said was that if you don't know what you are doing you could mess up your car or worse you could hurt yourself or someone else. Opening up the wrong valve such as the high side valve while charging can lead to an explosion since the high side pressure is more than what a can of refrigerant can with stand.

No, you actually stated that I didn't have a clue as to what I was doing. As a man who has built dozens of rare, hard to work on motorcycles, runs an AMA Pro Racing team and also a man who did all the service, including timing belt, cams, intake service and the thousands of other repairs to a 27 year old Porsche 928s, 32v motor and kept said car on the road for 13 years of ownership, I take offense to your post.

Maybe in your 600+ posts on this site, you have run across too many people who truly don't have a clue, I am not one of them. That's why I frequent forums like this to learn about things I am not that up on. Air conditioning systems are not my forte but I logically approach each and every job and rarely make mistakes. It's the people who don't ask questions that blow themselves up or burn down their own houses.

I like to offer up my advice and let the person run with it the best they can. If I don't have anything positive to contribute, I rarely say anything. Telling someone like me that I am out of my league is a cause for rebuttal. With all of my mechanical and electronic talents, I have never taken a class or been taught by an ASE mechanic. I am self taught and with a little research can fix anything from a DLP television, to a 928 to a BMW x5 including the air conditioning.

Having said all that, I DO appreciate the positive and useful information that you did provide.

Cheers
Bernie

If you had a clue on how to service an AC system you would have known that when you evacuate the system you will need to draw a vacuum to remove any water vapor that may have entered into the system when you opened up the system to replace the valve. You would have also known that whenever you open the system you would need to replace the receiver/drier. I only said that you didn't have a clue on how to service the ac system. If you did you wouldn't be asking all these questions.

I'm not the only one on this forum that suggested to you thta you should take it in to a tech that know what they are doing.

Here's a thread were I helped another owner fix his AC.

http://www.xoutpost.com/bmw-sav-foru...-question.html

I guess since you take offense to me I will just ignore all your future requests for help.