A/C Hissing
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Joined: Nov 2004
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'98 E320 4Matic, '85 380SL
A/C Hissing
Hi Everyone,
I sold my '80 450SL a few months ago, and am the proud new owner of a 1998 E320 4Matic sedan w/103k miles. I have a question about the air conditioning. When I turn on the A/C, I hear a hissing noise for a few seconds. Is this normal? I searched the archives and found someone who reported hearing a similar noise, but there wasn't any further discussion.
Thanks.
I sold my '80 450SL a few months ago, and am the proud new owner of a 1998 E320 4Matic sedan w/103k miles. I have a question about the air conditioning. When I turn on the A/C, I hear a hissing noise for a few seconds. Is this normal? I searched the archives and found someone who reported hearing a similar noise, but there wasn't any further discussion.
Thanks.
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From: Santa Clarita, CA
1987 E300 TD
What PSI was the high side of the freon line set to, if you know? I'm going to take my car to my schools auto shop and do it myself.....I would ususally fill it to about 220 PSI. But yeah, if you can tell me what PSI you filled yours to maybe I can it with a little extra freon. Do you know what it was previous filled to in PSI maybe like 90-100?
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From: Dallas, TX
2008 E63 wagon (1 of 62)
What PSI was the high side of the freon line set to, if you know? I'm going to take my car to my schools auto shop and do it myself.....I would ususally fill it to about 220 PSI. But yeah, if you can tell me what PSI you filled yours to maybe I can it with a little extra freon. Do you know what it was previous filled to in PSI maybe like 90-100?
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MBWorld Fanatic!
Joined: Mar 2007
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From: Santa Clarita, CA
1987 E300 TD
do you know the specs of freon needed for a 1999 E300 TD? I have yet to find it....good point about not bothering to mess with pressures, don't want to blow up anything!
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'98 E320 4Matic, '85 380SL
To do it right, you need to vacuum out all the refrigerant and refill with the correct amount (1 kg). Our cars have variable displacement compressors, which means that there is no way to know when the system is filled based on pressure. On a cool day, high side pressure may run 6-8 bar. On a hot day, it can be near 20. The high side pressure varies considerably depending on load. If you're insistent on recharging it by the seat of your pants, I'd suggest setting the fan to a low to medium speed and adding refrigerant until hissing noises disappear.
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ML
Hi Everyone,
I sold my '80 450SL a few months ago, and am the proud new owner of a 1998 E320 4Matic sedan w/103k miles. I have a question about the air conditioning. When I turn on the A/C, I hear a hissing noise for a few seconds. Is this normal? I searched the archives and found someone who reported hearing a similar noise, but there wasn't any further discussion.
Thanks.
I sold my '80 450SL a few months ago, and am the proud new owner of a 1998 E320 4Matic sedan w/103k miles. I have a question about the air conditioning. When I turn on the A/C, I hear a hissing noise for a few seconds. Is this normal? I searched the archives and found someone who reported hearing a similar noise, but there wasn't any further discussion.
Thanks.
MBWorld Fanatic!
Joined: Oct 2002
Posts: 1,560
Likes: 1
From: Columbia, SC
E300
IT's very easy to add refrigerant ot the system. First off getting a simple pressure guage is essential to measuring the high pressure end of the system. I found a usable unit @ Walmart. Then make sure to have a can or 2 of freon, depending on how low your system is. Then, on the climate control panel, set the diagnostic to the display that shows the refrigerant pressure, I forgot what itme it is, 7 I believe - On the gauge when adding the refrigerant you may see it go to the upper end of the safe zone which is ok. While adding the refregerant I always have the AC set to MAX cool while performing this process. If you add too much refrigerant you can always relieve the system. On the climate control panel I've found that the correct amount of refrigerant yields a pressure value, in the middle to lower teens BAR. When the compressor is first engaged after starting the engine and the car sitting the pressure reading shoudl reach the upper teens maybe low twenties. I have found from a prior experience that when the compressor engages and if the pressure value reaches 30, the compressor itself will cut-off. If this happens you know you need to relieve the system of some refrigerant.
Hope that assisten some in their quest of keeping cool :-)
Hope that assisten some in their quest of keeping cool :-)
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Joined: Nov 2001
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ML
IT's very easy to add refrigerant ot the system. First off getting a simple pressure guage is essential to measuring the high pressure end of the system. I found a usable unit @ Walmart. Then make sure to have a can or 2 of freon, depending on how low your system is. Then, on the climate control panel, set the diagnostic to the display that shows the refrigerant pressure, I forgot what itme it is, 7 I believe - On the gauge when adding the refrigerant you may see it go to the upper end of the safe zone which is ok. While adding the refregerant I always have the AC set to MAX cool while performing this process. If you add too much refrigerant you can always relieve the system. On the climate control panel I've found that the correct amount of refrigerant yields a pressure value, in the middle to lower teens BAR. When the compressor is first engaged after starting the engine and the car sitting the pressure reading shoudl reach the upper teens maybe low twenties. I have found from a prior experience that when the compressor engages and if the pressure value reaches 30, the compressor itself will cut-off. If this happens you know you need to relieve the system of some refrigerant.
Hope that assisten some in their quest of keeping cool :-)
Hope that assisten some in their quest of keeping cool :-)
And you think this easy to do for anyone out there? You have to be joking. Unless you write up a complete procedure, there's no way any newbee out there can use this - they'll probably blow a hole through themselves before completing the job. Also isn't the some kind of law in the US regarding purchase/handling of these refrigerrants - I don't know, just asking.
BTW, I think he has a leak. I don't believe any amount of refrigerant added will permanently solve the problem - unless he subscribes to an annual refill program. These systems are not supposed to hiss under any condition, period. If they do, there's a problem somewhere.
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Joined: Oct 2002
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From: Columbia, SC
E300
And you think this easy to do for anyone out there? You have to be joking. Unless you write up a complete procedure, there's no way any newbee out there can use this - they'll probably blow a hole through themselves before completing the job. Also isn't the some kind of law in the US regarding purchase/handling of these refrigerrants - I don't know, just asking.
BTW, I think he has a leak. I don't believe any amount of refrigerant added will permanently solve the problem - unless he subscribes to an annual refill program. These systems are not supposed to hiss under any condition, period. If they do, there's a problem somewhere.
BTW, I think he has a leak. I don't believe any amount of refrigerant added will permanently solve the problem - unless he subscribes to an annual refill program. These systems are not supposed to hiss under any condition, period. If they do, there's a problem somewhere.
The refrigerant is available @ Wal-Mart. Older R-12 I believe refrigerant is banned, well very difficult to get....
Depends on the age of the sytem, etc.... I have to add some refrigerant to my system, not a lot, but a top off is required. I can tell as the system doesn't cool down as promply and there is that audible "hiss"
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Joined: Oct 2002
Posts: 1,560
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From: Columbia, SC
E300
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Joined: Feb 2007
Posts: 809
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From: Dallas, TX
2008 E63 wagon (1 of 62)
depending on the age of the car, the locations for the 2 fill ports are in different areas. There is the one by the shock tower and the other may be down by the compressor itself, possibly down by the receiver/drier, or behind a small plastic panel infront of the radiator/condenser by the drivers side of the fans.
