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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 05-02-2010, 06:56 PM
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Fudman Fudman is offline
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A/C help needed

My A/C was not blowing cold air. The compressor was kicking on but no cold air was coming out. The forum consensus was to simply add refrigerant. So I added some r134. The compressor was working because it took the refrigerant. I apparently added too much as the low side pressure appeared high (~60 psi on the low side at 75F, should be around 50 psi). I bled a little out (I know I shouldn't just let it out but it hit 90F here today and I was desperate) and the pressure is now fine, however, the compressor is not kicking on anymore. Is there any way to reset the high pressure safety switch? Should I just have a mechanic drain, pressure check and refill the system? Is this a sign something else is amiss? I really don't want to take it to the dealer. The system was fine in the fall, plenty cold. This is the last time I mess with the A/C!
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Old 05-02-2010, 07:26 PM
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540iman 540iman is offline
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I can't answer why the compressor is not kicking on, but suspect you still might be too high. However, I think you may have a different issue as if your compressor was kicking in then you were not TOO low on freon. If the compressor was kicking on and no cold air I suspect a problem with the blend doors. Low freon (as long as it is not below minimum) will cause air to actually be colder- until you have a high humidity day and your evap. coil freezes over.
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Old 05-03-2010, 07:52 AM
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Since I overcharged the system, I am wondering if I caused the refrigerant to become high on BOTH the low pressure and the high pressure side. The compressor has not operated since I loaded the refrigerant. I bled some refrigerant off the low pressure side but did not (and will not) touch the high pressure side. Would this cause the high pressure safety switch to prevent compressor activation? If yes and I take this to an A/C service shop, they could bleed off the high pressure side and the system should in theory work again. I just fear taking it to a stealer who will tell me I have to replace everything for $2000. Any thoughts on this?
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Old 05-03-2010, 08:42 AM
edjack edjack is offline
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You need to bleed off refrigerant until the evap exit air temp is 4 deg C, as measured at the evap. Since you'll need a MoDIS to do this, the best you can do is measure at the center dash vent. Try for 10 deg there, but this will depend on the dashboard temperature.

Unless there's a leak somewhere, these systems are very tight. Mine has not been charged since I bought it in '01, and it still blows cold. Also, being an automatic system, there are other possible causes for no cooling besides low refrigerant.

Just hope you didn't inject some air along with the refrigerant.
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Old 05-03-2010, 11:15 AM
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Does your outside temp sensor work or does it read -40 degrees? Just checking--if the car "thinks" it's very cold outside the HVAC will not allow you to cool your car; this has come up here frequently.
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Old 05-03-2010, 05:49 PM
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Quote:
Originally Posted by Fudman View Post
My A/C was not blowing cold air. The compressor was kicking on but no cold air was coming out. The forum consensus was to simply add refrigerant. So I added some r134. The compressor was working because it took the refrigerant. I apparently added too much as the low side pressure appeared high (~60 psi on the low side at 75F, should be around 50 psi). I bled a little out (I know I shouldn't just let it out but it hit 90F here today and I was desperate) and the pressure is now fine, however, the compressor is not kicking on anymore. Is there any way to reset the high pressure safety switch? Should I just have a mechanic drain, pressure check and refill the system? Is this a sign something else is amiss? I really don't want to take it to the dealer. The system was fine in the fall, plenty cold. This is the last time I mess with the A/C!

You kept the can with the valve on the top right side up at all times correct so that only gas, not liquid entered the system? Before you charged, with the system operating one of the pipes will be hot, the other cold. Did you check?
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Old 05-03-2010, 06:40 PM
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540iman 540iman is offline
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I believe you misunderstand the relationship between the high and low side pressures. One is dependant on the other. Ambient temperature and humidity will affect both, but ignoring the outside temperature for a minute...As you start adding freon (let's assume for a minute that the system is empty and has been under a vacuum) the low side pressure will begin to rise from zero to say 40#. During this time, when sufficient freon is added to trip the low side pressure switch the compressor will kick in and the high side pressure will be say 200psi. The number does not matter for now. At say 20psi of low side pressure caused by the initial adding of freon the compressor will kick in and you will get a high side reading. As you add more freon past the 20# it took to get the compressor to run, the high side will rise as well, but much faster. At say 30# on the low side, you might have 250 on the high side. 40# on the low side might yield 300# on the high side (depends on outside temperature) At some point, the high side limit switch will cut the compressor off to protect the system. You can not bleed off pressure from just the "low side"-- you always affect both. System will not run if too low or too full of freon. Oh, and adding liquid freon to a system is done all the time. It is better to add as a gas, but you can turn the can upside down and add as a liquid and it will revert to gas in the system. Adding freon as a liquid will not ruin the system. A/C techs do it all the time to speed up charging a system. You just need to be aware that you are going to increase delivery of freon and pressures more rapidly.

Last edited by 540iman; 05-04-2010 at 06:58 PM.
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Old 05-04-2010, 03:59 AM
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Thanx for the responses.

The outside ambient temp guage is fine. Temps are reading normal.

I refilled the R134a both right side up and upside down, per the can's instructions, so both liquid and gas was charged (including the lubricant).

I've been talking with a guy that does A/C work. I asked him to remove the R134a, do a pressure check and then refill the refrigerant. His concern is that if the compressor is not working, he will not be able to refill the system. He will run a diagnostic on the A/C system shortly. I am hoping that since the compressor was running properly (as I was able to charge the system), there should be no component failure in the system
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  #9  
Old 05-04-2010, 06:49 PM
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You need to find a real hvac repair guy. With all due respect. If he does not know how to fill an empty system, then he isn't worth the change in your pocket. I'm sorry, but how does he think you fill a system after a compressor change? Maybe you misunderstood him. Tell me what your low side pressure (or high side pressure for that matter as if the compressor has not been running they will be the same anyway) is now if you can. We can then decide whether you are too full on freon. Generally speaking, when you have too much freon in the system, the compressor will start momentarily and then shut down within a few seconds. I unfortunately can't speak to the BMW system, but I can speak to
R134a and the pressure-temperature relationship which is the same no matter what system it is in. I will need to know the temperature and approx. humidity at the time you check it as well, but only if it is extremely humid or extremely dry. Otherwise the humidity will not affect it that much. I can at least tell you whether it is likely that you need to bleed off more. Also, if you asked your same HVAC guy to take the 134a out you would then vacuum test the system, not pressure test it. Semantics I know, but we need to get you understanding what this is all about and that is what the forum is for. Unfortunately you can et some bad or incorrect information as well from folks that mean well, but don't know what they are talking about. I'll try and walk you through this if you want me to.

Bill
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  #10  
Old 05-05-2010, 03:56 AM
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That's a good point. He is supposed to be an A/C specialist, recommended to me by my Honda mechanic (kid's car), who has a Honda specialty shop. However, his logic was not exactly clear. I seem to recall that the pressure was down to about 45-50 psi when the air temp was around 80-85 F but the car's ambient temp guage was reading 76F. Humidity was average. I will recheck the pressure tonite. Thanx.
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  #11  
Old 05-05-2010, 08:41 PM
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take it to an a/c, radiator shop, the kind that does only this kind of repair. and btw did you check the fuse and relays?
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Old 05-06-2010, 04:01 AM
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Yep, fuses and relays check out OK. This A/C guy I went is what you would characterize as somewhat "eccentric". He works out of his house. I usually find these folks to be exceptioanlly good at what they do or completely useless. I really think that my problem is simply overcharging the system and that a drain, vacuum test (to confirm proper function) and refill should do the trick. Time to find a real A/C pro. Thanx.
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Old 05-06-2010, 06:37 AM
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Does your car have a sun sensor ? It's part of the windshield...could be what's affecting compressor activation.
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Old 05-08-2010, 07:09 AM
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540iman 540iman is offline
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Fudman,

Do you have a guage to check the pressure? Do you want help with this or what? If you don't have a guage or want assistance I'll unsub this thread! Just trying toget you going and save you he expense of an HVAC guy-especially one that may not have a clue what they are doing and may really lead you astray.
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Old 05-08-2010, 11:02 AM
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Bill:
Sorry for the delay in responding. Too many things going on. Spent the AM replacing my emergency brake on the Explorer. Enough of the excuses.

The outside temp is now 55F, The car's outside temp guage reads 61F. Humidity must be around 80-90% as it has been raining today. I have a cheesy guage on the end of the refrigerant can that says the low side pressure is around 48 psi. I suspect that it is still too high. The label on the can says at 65F, I should be at 25-35 psi. Do you concur?

Last edited by Fudman; 05-13-2010 at 01:14 PM.
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Old 05-13-2010, 01:17 PM
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I finally replaced my (lost) Peake and ran the codes: 19 7d. Item 7d in Table 19 says: E-fan. Does anyone know if this is this related to my A/C issue or should I be looking at my cooling fan? I thought the e39 had the pulley driven fan and the e36s had the electric fan.
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Old 05-13-2010, 01:42 PM
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Fudman, I have the Peake reader as well.
What I do to double check, i do convert back to standard OBD II codes (they have the explanation somwhere at the back of the Peake manual, I think). You have to convert from sexagesimal to decimal if I'm not mistaken. Then, maybe the code would make sense.

Cheers
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Old 05-13-2010, 05:40 PM
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Quote:
Originally Posted by Fudman View Post
I finally replaced my (lost) Peake and ran the codes: 19 7d. Item 7d in Table 19 says: E-fan. Does anyone know if this is this related to my A/C issue or should I be looking at my cooling fan? I thought the e39 had the pulley driven fan and the e36s had the electric fan.

Newer E39 A/C doesn't work unless the pusher fan is good, this is your main problem.
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Old 05-13-2010, 06:41 PM
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Newer E39 A/C doesn't work unless the pusher fan is good, this is your main problem.
OK, that is starting to make some sense, as that aligns with the code I pulled. The pusher fan sits in front of the condenser. Anyone have any ideas as to what would cause the pusher fan to stop working? Fuse? Is it somehow related to my overcharging the A/C system? There is nothing on this in my Bentley. My current system (low side) pressure is now around 35 psi at around 65F-70F, so the compressor should kick on but is not.
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Old 05-13-2010, 07:26 PM
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Originally Posted by Fudman View Post
OK, that is starting to make some sense, as that aligns with the code I pulled. The pusher fan sits in front of the condenser. Anyone have any ideas as to what would cause the pusher fan to stop working? Fuse? Is it somehow related to my overcharging the A/C system? There is nothing on this in my Bentley. My current system (low side) pressure is now around 35 psi at around 65F-70F, so the compressor should kick on but is not.
Here are some of the probabilities why pusher fan doesn't work

Fan Controller, the fan controller is inside the fan ass'y, you can not just buy a controller, you have to buy a whole fan ass'y, and when it comes to these fans go OEM or go home.

You can check fuses just for good measure and also check the pusher fan plug just behind the grill and top right radiator for corrosion.
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Old 05-13-2010, 09:27 PM
Rjim Rjim is offline
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Originally Posted by 16valex View Post
Newer E39 A/C doesn't work unless the pusher fan is good, this is your main problem.
From the electrical standpoint, this is correct. Having just gone through a bunch of BS with my aux fan, I can confirm if your aux fan is not getting current through fuse #75, your A/C will not work. I believe A/C compressor and aux fan are on the same circuit. I know this to be the case on my '03 530i.
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Old 05-14-2010, 04:50 AM
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Thanx, guys. I will check into this tonite.
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Old 05-14-2010, 10:24 AM
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Originally Posted by doru View Post
Fudman, I have the Peake reader as well.
What I do to double check, i do convert back to standard OBD II codes (they have the explanation somwhere at the back of the Peake manual, I think). You have to convert from sexagesimal to decimal if I'm not mistaken. Then, maybe the code would make sense.

Cheers
Hi -

First, thanks for using our products!

Just a quick point of clarification - using our manual to retrieve code definitions, there is no need to attempt a translation to generic OBDII P codes. This is a bit like taking a well written sentence in English, translating it to Chinese, then back to English. Something will most definitely get lost.

The hexadecimal conversion is simply used to convert the output of the BMW code number to the 2 (or 4) digit alphanumeric output that gets displayed on our tool. It has absolutely nothing to do with generic OBDII.

I hope that helps clear things up a bit.
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Old 05-14-2010, 10:49 AM
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540iman 540iman is offline
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Fudman, I would say your pressures are fine. I am surprised by how much difference there was between two different days checks. 61 pounds is a tad high, but recall that a system that has not run in a long time will have a higher low side pressure as all the freon on the high side will leak back to the low side until the pressures are equal. A system that is run often and is "tight" might show 35 and 250, and the same system left unrun for a long time might check 65 and 65 low and high side respectfully. E39s have the auxilliary fan in front protected by a 50 amp fuse above the glove box. Depending on what year you have, you could have three large resistors for the three seperate speeds or the later models are controlled by the DME so they are VERY difficult to test. I tried every which way to get my fan to run off my battery charger which easily puts out 35 amps or more and it would not power it, yet the DME turned it on beautifully! The newer fans will have three wires going to them. Two good size wires Like #10 and one puny wire from the DME to control speed. You can just buy the motor. I believe Auitozone sells. Do a search. It may just be the older style fan which regulates speed through the resistors. I was not aware that the fan being dead would stop the AC from turning on. It only turns aux. fan on at idle when hot and for about 30 seconds after you shut off car when running ac.

Since your AC was running before, I would definitely let out about 10# from the low side. Do it in steps. The stuff to fill it again is dirt cheap so don't sweat a little waste. Tell your neighbor you bought some pollution credits from a steel mill =) The fan job is a PITA as it requires you to pull the front bumper. You should be able to go as low as 25# and still have enough in there to run the compressor. You could locate the low side pressure switch and jumper it out as well. Just let some out and move on! I was out of town for a while. Will be available all weekend if you need me.
Bill

P.S. whatever you do, do NOT turn the freon can upside down!!! Jeez, the mis-information here is unreal. It generally comes from the most critical people too that have no idea what they are talking about, but will never admit they may have given you bad information because they are always right and they refuse to argue with idiots. This could explain why you see them talking to themselves a lot..
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Old 05-14-2010, 12:04 PM
Waveho Waveho is offline
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Originally Posted by 540iman View Post

P.S. whatever you do, do NOT turn the freon can upside down!!! Jeez, the mis-information here is unreal. It generally comes from the most critical people too that have no idea what they are talking about, but will never admit they may have given you bad information because they are always right and they refuse to argue with idiots. This could explain why you see them talking to themselves a lot..
Woah there! Talk about misinformation being unreal here! Whether the R134a refrigerant should be added upside down or rightside depends entirely upon the kind of container--you must read the instructions! Some cans MUST be upside down to dispense and certain cans/containers must be rightside up.

Also, I would HIGHLY recommend that a non-trained person NOT attempt to add R134a to the high pressure side. This is dangerous if you don't know what you are doing. In fact, all the recharge kits you'll find at places like AutoZone and KMart, etc. will ONLY include an adapter for the LOW side. That adapter will not allow you to add refrigerant to the high side--they are different sizes, and for very good reason. You can get a high-side adapter at some professional shops or online. But remember that people lose eyes and teeth all the time trying to charge their system from the high side. You must wear goggles and I suggest work gloves when doing any of this.
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