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Old 07-15-2008, 08:28 PM   #1 (permalink)
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1997 540i A/C help

My 97 540i keeps blowing hot air through the a/c vents. The A/C system is fully pressurized, condenser has no leaks, compressor is working, evap. is working, yet the system is still blowing hot air. It almost seems that freon is not fully circulating through the system. Can anyone provide me with any information that will help me.

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Old 07-15-2008, 09:06 PM   #2 (permalink)
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aside from what has been posted above:

*fully pressurized... i quite do not know what u mean by that- OVERCHARGING your a/c system will also cause hot air to blow.

*fully pressurized... can also mean, your system maybe "full" and pressurized; but also if it contains moisture... it will blow hot air
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Old 07-16-2008, 01:07 AM   #3 (permalink)
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do you know the High and low side gauge pressures? also feel the lines going in and out of the evaporator(In the engine bay going to the evaporator.) also look at the A/C dryer does it had water or Ice on it? thanks.... also how much was the system charged with? also on LAST question..... It the button with the A/C button (the one with the snowflake) sry..... My mom said mine wasn't working and she just didnt know t hit that button...(it should be lite)
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Old 07-16-2008, 07:54 AM   #4 (permalink)
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Darkhorse, what do you suggest....bleed the whole system, and if I do have moisture in the line, how do I get rid of it.

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Old 07-16-2008, 09:11 AM   #5 (permalink)
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First, i would make sure that the electric valve, (see that link i sent you earlier) is properly working and not at fault.

Second, test your A/C from under the hood: run engine and switch on A/C. check also to see that the magnetic clutch on ur A/C compressor has actually engaged. (not engaged... check fuses!)

If yes, U will see two A/C lines leading to the firewall(actually to the evaporator inside the cabin). with engine running and A/C ON, the smaller line(HI side)should warm/hot, and the bigger line(LO side)should be icy cold.

If the above conditions are not met, then your prob will be 1 or more of the following:
1) overcharge- meaning too much liquid freon in system, meaning there is no chance for the freon to convert to gas; therefore no cooling is possible;

2) too much refrigerant oil or wrong oil in system - u suspect this if you've jst recently had your A/C system serviced

3) moisture in system -

4) expansion valve restriction -

* What was the manifold reading for HI & LO side when you tested? Or, how do you know it is "fully pressurized"?

Best suggestion i can give, is to have your system, evacuated, vacuumed(to expel moisture and air in system), then recharge with 1225 grams +/- 25 grams of R134a refrigerant.
...after this is done, and you are still having probs, consider removing and replacing both filter drier and expansion valve.

Let me know what you find; Good luck to you :-)
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Old 07-16-2008, 09:14 AM   #6 (permalink)
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Quote:
Originally Posted by AlpineSixAndSeven View Post
do you know the High and low side gauge pressures? also feel the lines going in and out of the evaporator(In the engine bay going to the evaporator.) also look at the A/C dryer does it had water or Ice on it? thanks.... also how much was the system charged with? also on LAST question..... It the button with the A/C button (the one with the snowflake) sry..... My mom said mine wasn't working and she just didnt know t hit that button...(it should be lite)
hehehe, alpine... funny u mentioned that. I was helping a friend fix the A/C on his van and for awhile i cdnt get the compressor working.... but YES, i forgot to flick the A/C button. LOLZ
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Old 07-16-2008, 10:05 AM   #7 (permalink)
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Darkhorse, is the expansion valve and the control valve the same, also where would the filter drier be located...engine bay or behind the dash somewhere. I tried looking up the filter drier on the internet, could not pul up anything. Thanks again for your help
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Old 07-16-2008, 10:20 AM   #8 (permalink)
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Darkhorse, is the expansion valve and the control valve the same, also where would the filter drier be located...engine bay or behind the dash somewhere. I tried looking up the filter drier on the internet, could not pul up anything. Thanks again for your help
control valve is different. This is the electric valve that shuts out the coolant(hot water) from entering the heater core when in A/C mode.
TIP FOR YOU: if this valve is defective, even with a perfectly working A/C system, you won't have cooling.

Expansion valve is at the firewall, that aluminum block that you see if you follow those two A/C lines i mentioned in my earlier post. Facing your car, it's on the left side.

filter drier(aka receiver drier) you will need to remove right headlight to expose it.

Are you doing the work yourself? If yes, tell me first the manifold pressure readings before u start the work. I might be able to coach you better if i know the readings ;-)

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Old 07-16-2008, 03:11 PM   #9 (permalink)
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things were going to need to help you...
high and low Pressures with the system off Also if the
high and low Pressures with the system on
How much the system was charged with
When you notice it not working (slowly died or one day just stopped)
what has been done in the last year or so...
are the lines comming in and out for the cabin hot or cold(largerline should be cold smaller should be luke warm)
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Old 07-18-2008, 08:38 PM   #10 (permalink)
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darkhorse, here are the readings...the high side was 65psi and the low side read 50psi.
Both lines started out at about 100 psi, then I bled them down to the numbers above.
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Old 07-18-2008, 11:47 PM   #11 (permalink)
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HI side 65psi with engine running???

waah*... 1 of 2 things. u lack refrigerant.... or if u have loaded 2 1/2 to 3 cans already, and u still get 65 psi on th HI side, your compressor is bad.

without mentioning any figures... picture an A/C manifold guage blue meter on the left(LO side) and red meter on the right(HI side)... with the right amount of refrigerant and all components of the A/C circuit in a normal wroking state; both needles should be pointing between 9:30 and 11:30 on a clock scale(short hand of a clock).

If the needle should be under or above that range, there is something wrong.
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Old 07-20-2008, 03:56 PM   #12 (permalink)
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darkhorse,
I evacuated the sytem and added 1 can and the system was reading about 100psi on the lo and hi side and won't take any more. Even though the compressor clutch is engaging, does this mean the pump is not pulling the refrigerant through.
If the ac drier is bad or plugged, will it do the same thing
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Old 07-20-2008, 11:01 PM   #13 (permalink)
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Quote:
Originally Posted by chili12672 View Post
darkhorse,
I evacuated the sytem and added 1 can and the system was reading about 100psi on the lo and hi side and won't take any more. Even though the compressor clutch is engaging, does this mean the pump is not pulling the refrigerant through.
If the ac drier is bad or plugged, will it do the same thing
100psi... engine running compressor engaged; or 100psi engine off??(Both HI & LO side will always have equal readings with engine not running...)

i'll answer you in 2 ways because reading with engine running/compressor engaged vis-a-vis reading with engine off makes a whole lot of difference.

ENGINE OFF:
100psi for both HI & LO side after loading 1 can would appear as normal.

ENGINE RUNNING/MAKE SURE COMPRESSOR ENGAGED:
100 psi at HI side & 100 psi reading on the LO side means that even if your clutch is working, the compressor may be faulty; OR... the expansion valve or receiver drier is clogged. (a good rule of thumb in reading manifold guages is 30-40 a the LO side and around 180 or higher at the HI side)

*visually check to see that the center bolt at the center of the clutch is actually turning when A/C clutch is engaged.

TIP FOR YOU: remember that you dealing here with a "closed" system and what happens inside it isn't visible to the eye... Unfortunately, the manifold readings give u a hint as to what might be wrong, but cannot pinpoint what part and where the fault is exactly(i.e. the clog could be in the parts mentioned, but could also very well be in the lines)... AS such, changing part per part as you go in the hope that you will find you "cure" is laborious and expensive.

The most practical way to attack your problem is to open the system:
1) test the compressor. If the center will turn freely by hand, and when u turn by hand, the "S" side will have suction, and the "D" side will push pressure when you turn we assume it to be good.
2) change the receiver drier. It's responsible for ridding your system of moisture(any air/moisture in system renders your A/C inoperative). It's cheap. $18-25.- at your fave auto shop.
3) change expansion valve. it's usually a problem part when we talk of clogging... beacuse it's job is to force freon through a very tiny opening to provide the "cool" we look for. THE AVERAGE COST IS ABOUT $35-45.00
4) while the receiver/dryer and expansion valve are still out, blow all of your lines with compressed air, or flush if possible. This is to check whether your lines are actually free of debris. If at anytime, compressed air cannot pass through say the evaporator lines, or the condenser lines, then you have found THE clog in your system ;-)

5) if the lines, evaporator, and condenser pass compressed air freely... then let's start ur re-install. :-)
6) renew all the o-rings ith A/C grade o-ring seals. make sure they are oiled with PAG or ester oil before install so they don't bind in their sockets, and also to improve the sealing quality.
7) re-install expansion valve & receiver/drier.
8) vacuum and test ur system for leaks. A good job will show in the amount of vacuum your system can pull. Within 15 mins of applying vacuum, your system should be able to hold a 30in. vacuum(it should show on your manifold guage- the negative #'s on the LO side scale is what u use for this)
9)close both manifold knobs, and disconnect vacuum. Observe the meters. Both high and low side meters should be able to hold their respective positions in a negative reading for at least 10 mins.
10) if YES, it is holding - CONGRATS, you did a good job and are now ready to re-charge your system with new R134a; if NO, needle moved leftward to the "zero" mark, your system has a leak. RE-CHECK your work.
11) introduce you oil charge if u haven't done that when u tested the compressor, followed by the recommended amount of R134a which is in your case 1225grams +/- 25grams.

*it sounds complicated at fist, but all the above steps can be done in an hour. ;-)

Good Luck and have fun :-)

Last edited by darkhorse737; 07-20-2008 at 11:10 PM.
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Old 07-21-2008, 02:12 AM   #14 (permalink)
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Quote:
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darkhorse, here are the readings...the high side was 65psi and the low side read 50psi.
Both lines started out at about 100 psi, then I bled them down to the numbers above.
???? wha? 100psi every thing off then 65 and 50 when running? 65 is WAYYYYYYYYYYYYYYYYYYYYYY to low should be 150-200psi.... on the high side and 15-30 lowside! sounds like it is low....
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Old 07-21-2008, 07:46 AM   #15 (permalink)
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Thanks guys, I'll let you know how I make out
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