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2000 230C Kompressor
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Discussion Starter · #1 ·
Does anyone know which of the two ports for the R 134 A is the high pressure vs the low pressure? There is one under the grill/fan cover and one on the compressor itself. Common thought is the larger diameter line is low pressure and smaller diameter is high pressure. MB in their infinite wisdom does not mark them.:| and I know it is a bad idea to get them mixed up.
 

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96 MB C220
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On my 96 C220, it's down behind the power steering pump (and a bear to get to!). An easy fill once I got the hose in there, but not particularly easy to get to. I believe the only more annoying one I've dealt with was when I gassed up my sister's 2003 Ford Focus - you have to remove front right tire and part of the wheel well covering to get to that one. :)
 

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mine is in about the same location. it is hard to use those store recharge cans w/hose unless you have a longer hose.

normal 12" hose w/ attached can is tough to impossible to use. 24" hose would be better.
 

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1995 C220
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That is probably close to correct. Keep in mind that when the compressor kicks on, it is natural to see a drop in pressure. You can see as high as 300 psi on the high side, because the compressor is forcing the freon through a small hose size. It is also sucking from a larger line(the low pressure side), so it is expected to see a drop in pressure. Static pressure doesn't mean much to me except tell me there is freon in the system. Pressure while running on low side, I have seen as low as 20 and as high as 40 depending on the car, the ambient temperature, and the amount of air flowing through the condenser. But it sounds like yours is right in the sweet spot.
 

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1999 C43 AMG, 1998 C43 AMG
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That is probably close to correct. Keep in mind that when the compressor kicks on, it is natural to see a drop in pressure. You can see as high as 300 psi on the high side, because the compressor is forcing the freon through a small hose size. It is also sucking from a larger line(the low pressure side), so it is expected to see a drop in pressure. Static pressure doesn't mean much to me except tell me there is freon in the system. Pressure while running on low side, I have seen as low as 20 and as high as 40 depending on the car, the ambient temperature, and the amount of air flowing through the condenser. But it sounds like yours is right in the sweet spot.
This is 100% correct. The "lo" side is called "lo" because the pressure on that side drops when the system is operating normally. Inverse for the "hi" side (port accessible beside aux fans on the front).

When the system is not engaged and the compressor is not running, the pressure will match between the 2 sides, making the "hi" side drop and the "lo" side to climb.
 

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2000 230C Kompressor
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Discussion Starter · #11 ·
Again thanks everyone. The charging went off without a hitch and the fan is blowing cool air again. The gauge that came with the can had the pressure at 43 with the compressor running. And i got it fixed just in time for southern California's first cold spell in a long while.... ah... but we need the rain.
 

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1999 C43 AMG, 1998 C43 AMG
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Be sure you don't overpressurize the system. Your C280 could end up in a junkyard.

The evaporator is the weak point in any AC system. It's the first thing that gives away under high pressure. It's located in the dash and requires whole dash out to replace. $3,000 repair at most shops.

Get your hi side pressure checked before you pop your evaporator. If you do have a leak, pray it's not in the evaporator.

Many systems never develop a leak at all and all that goes wrong is either the compressor wears out, the condenser clogs up, the expansion valve siezes/clogs, or the receiver drier clogs.

The receiver drier is essentially a filter for the AC system. The system does NOT do well with moisture in the lines because it mixes with the gas and becomes corrosive, so the receiver drier filters out moisture that leeches in over the years. If the system has been in perfect health the entire time, it's most likely the receiver drier needs replacing. This is very common in a 10+ year old car. The receiver drier is clogged up and not allowing the system to pressurize correctly. What most people do is run down to autozone and buy a can of freon or one of those refill kits and put it in the system.

Due to the abnormally low pressure on the LO SIDE ONLY it will accept this new amount of freon. What's unknown in this process is just how high the pressure is on the hi side. If the drier is clogged, you just overfilled your system and it's a matter of time before something springs a leak.

Buy some gauges ($50), find someone who has them, or take it to a shop just to do a pressure test.

YOU WILL BE THANKFUL!
 

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Great information sulaco.

I had borrowed a set of gauges. I couldn't for the life of me connect it to the high pressure side. It kept on spraying refrigerant on me.

So I was only able to read the low side. It read about 34psi when AC was running and about 130psi when AC was off.

Can anything be inferred from that? I put about a can and a half (12oz cans) of r134 into it since it was a little low.

Not knowing the high side could I have put too much? What's the high side supposed to read under normal operations?
 

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I just went to a local gas station guy and asked to borrow his gauge. He plugged it in and my readings with the AC on it's lowest temp and blower speed at its highest:

Ambient temp: 87 degrees Fahrenheit
Low side pressure: 40 Psi
High side pressure: 205 Psi

Any comments welcome?
 

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OK. So, is there a way to increase my high end pressure? It increases to ~275psi when the compressor cycles off.

I see lots of bubbles rushing through my sight glass as the compressor cycles.

All this said, it does cool my car. Air is not ice cold but cold enough that I don't mind.
 

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No vacuum pulled. The psi numbers you see above is after adding 1.5 cans of freon a week ago.

Can I leave the system alone as-is now since the AC seems to be working fine. It's cool enough for me.

Or will the bubbles damage something?
 

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1995 C220
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The short answer as far as damage, is the potential is there. Vacuuming the system pulls the air out of the system, but more importantly, water boils at about 80 degrees when under a vacuum. So pulling a vacuum on the sytem will draw out any moisture that may be in the system as well. Leaving this moisture in the system is harder on the compressor and can break down the oil in the system, and will lead to premature failure of the compressor. I'm sure as to how long it will last depends on how much water is in the system.

The good news is that I was looking on harbor freight, and if you have a decent air compressor, they sell an air operated vacuum pump for about 20 bucks, or you can get an electric one for 100 bucks, if you want to attempt it yourself.

If you suspect your freon was just getting low, I wouldnt worry about it. But if you had a line loose and it was completely empty, I'd vacuum it.
 
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