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seville 96, Catera 97, eldorodo 97
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Discussion Starter #1
for my Eldo 97, AC clutch goes on when AC is turned on, Freon low side pressure is about 100 PSI, but no cooling. Not sure that when clutch is runnning if compressor is really compressing or not. Any idea what should I check. I tried to load freon, but it does not take since low side pressure is about 100psi.

Thanks
John
 

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2000 Eldorado ESC
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What's the high side pressure? Could be a bad compressor if the high side is also 100 psi.
Need to know what the high side does. What happens if you raise the rpm, does the low side move at all?
 

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2000 Eldorado ESC
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Low side is suction, so there's not enough suction. High side is discharge.
If the high side is 100,
then....... it's not "compressing". Don't know without high side pressure info.
If you discharge the system, check the orfice tube as well.
Has the air ever worked?
 

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seville 96, Catera 97, eldorodo 97
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142 Posts
Discussion Starter #5
I am out of town so could not check the high side pressure. I suspect it is blockage, so may be the orifice tube needs to be changed. I guess it is in the evaporator. Any idea how to change the orifice tube. Also how to access the evaporator to access the orifice tube. I highly appreciate your resopnses Thanks

John
 

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2000 Eldorado ESC
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The orifice is in this tube, left of the fitting. Make sure to observe what direction it's orientated, installing it in the wrong direction will damage the pressure sensor. A blockage would cause the low side to pull vacuum, It may be stuck fully open. I know expansion valves can do this. I would replace the orifice, if you still have 100 psi then I would suspect the compressor.

 

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seville 96, Catera 97, eldorodo 97
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Discussion Starter #7
Clarkz71,

Thank you so much. How can I access this orifice tube. Is it accessed from inside the car or is it accessed by opening the engine hood. Also when I replact the orifice tube, will the freon be lost. Are there any special precautions before I replace orifice tube.

Thanks
John
 

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White Diamond '03 DHS (with DTS floor shift)
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86,994 Posts
You access the orifice tube by opening the line at the coupler in the picture (on the firewall). Yes, you will vent the refrigerant. It should be recovered rather than vented to atmosphere (illegal). Once replaced the system needs to be vacuumed down before recharging.

Reread the 2nd sentence in Clark's post (#6) for precautions.
 

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seville 96, Catera 97, eldorodo 97
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142 Posts
Discussion Starter #9
Ranger,

Thank you. Is there anyway I can vacum down after changing orifice myself. Is there any chep too available to vacume it down or is it I have to get vacumed from a car repair shop?

Thanks
John
 

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2000 Eldorado ESC
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Clarkz71,

Thank you so much. How can I access this orifice tube. Is it accessed from inside the car or is it accessed by opening the engine hood. Also when I replact the orifice tube, will the freon be lost. Are there any special precautions before I replace orifice tube.

Thanks
John
As Ranger said, you unscrew the large fitting, hold the smaller (left) as it's fixed with a wrench and loosen the large fitting with another wrench. Pull apart the pipes and the orfice is in the left pipe (evap tube). Use a pair of needle nose pliers to remove it.
 

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1999 Black and Tan STS
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How come I do not see a low pressure port on my 99 STS? My High side is at 150 now. I have the guages needed but no placw to connect low.
 

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White Diamond '03 DHS (with DTS floor shift)
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Look closer. I've done it on a '99, but can't remember exactly where it is. Should be near the accumulator I believe.
 

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2008 SRX
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403 Posts
Low side is suction, so there's not enough suction. High side is discharge.
If the high side is 100,
then....... it's not "compressing". Don't know without high side pressure info.
They don't call it an A/C suction, compression unit.... they call it a comprressor. If it is doing one, it is doing the other.
If it is engaged and the low side is at 100 psi it is not 'working' , unless it is seriously overfilled.
Replace the compressor and orifice. There is no expansion valve to stick open and there is nothing tricky about this.
 

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2000 Eldorado ESC
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They don't call it an A/C suction, compression unit.... they call it a comprressor. If it is doing one, it is doing the other.
If it is engaged and the low side is at 100 psi it is not 'working' , unless it is seriously overfilled.
Replace the compressor and orifice. There is no expansion valve to stick open and there is nothing tricky about this.
I don't know how long you've been working on cars, but on almost any compressor dating back to the old York's the ports are marked "S" for suction or low side and "D" for discharge or high side. And if you read my post I didn't call it a "suction", I called it a compressor. In any case I'm not a parts replacer. I diagnose a problem before replacing an expensive part. And an orifice tube does the same job as an expansion valve, controlling the flow of refrigerent through the evaperator. And last, I did say you probably need to replace the compressor.
 

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2008 SRX
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All I'm saying is that on a CCOT system, if there is no suction then there is no compression. That's just the way it is with a fixed orifice. I'm not one to just throw parts at cars either, but this one was 99% diagnosed by reading the title. In my 20 yrs with Cadillac they've primarily used CCOT systems so I have minimal experience with expansion valves but I've seen them act like a weak compressor because they stick open. :)
 

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2000 Eldorado ESC
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OK, I can agree with you there. The main thing I was trying to tell the guy was to check both low & high side pressure when diagnosing an a/c problem.
Being a Mercedes tech most of my experience is with expansion valve systems. (TXV)
 
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