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MB compressors last 30 years/300k miles even in California (when they work hard 10 months each year) so I would not assume anything base on age.

When my father immigrated to USA (that was "few" years ago) he brought his Polish engineers diploma with him.
But becouse of poor english, he started doing odd jobs.
Couple years later he become fluent in english and applied for a job at designers office.
He show his Polish diploma to manager, but he replied
"I don't care about your foreign diplomas. If you are engineer - go to drawing board and show me".
So when it is coming to you 2 >>> I am still waiting ;)
 

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Here is what I see on the diagnostics:

Cold engine off Cold engine On Hot engine off Hot Engine On
84 85 87 82
78 80 100 93
89 85 91 71
89 85 91 67
87 82 93 84
94 102 204 204
07 07 10 10
84 85 127 118
27 35 27 27
2.5 2.5 3.1 2.3
2.5 2.5 2.5 2.5
4.3 4.3 4.3 4.3
3.2 3.2 3.2 3.2
32 46 32 44
0 0 0 0
32 32 211 211
11.2 13.3 11.1 13.1
164 164 164 164
85 85 85 85
40 40 40 40
136 136 136 136
 

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Your calibration show temp sensor having 11 degrees spread, or even 20 if you consider engine temp.
That might be due miscalibration, or might be due the test taken before car temp stabilized. You need to answer that.
Than when your cores show some cooling, the engine shows 204F, what is high.
I am not sure at what temp computer disengage the AC, but that might be the culprit.
Do the last test by letting the car sit on hot parking for at least 1 hr, than display #7, start the engine and observe how the pressure change in next couple of minutes.
Make sure all codes are cleared and engine is below 80C on restart.
 

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Temperature is 98 outside.
1st reading for value 7 is 9. Within 5-10 secs it reached 10.
It stays at 10 for the next 5 minutes -- Very hot air is blowing out.

Regards
 

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If the clutch is engaged and compressor doesn't pump more than 10 bars, that would mean compressor is kaput.
If you could get mechanical gauges on both sides, that would make for final confirmation.
Too many things in those tests go sideway, so final confirmation is highly advised.
 

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A new compressor on Ebay is around $100, should I just change that since I do not have too much mechanical aptitude (EE), an the Mercedes diagnostics is $135 ?
Any other parts I should change, other than the refrigerant.
 

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:grin:grin:grin:grin

Then, there are those who need a GPS to go to their local stores, and still manage to get lost :)

For reference, the ECU will send an "emergency mode" command through the Instrument Cluster to the a/c controller when the coolant temp reaches 117 degrees C for stage 1 (20 second off 20 second on), and 120 degrees C for stage 2 (compressor is off permanently). 204 degrees F = 95 degrees C which is NOWHERE near that.
 

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A new compressor on Ebay is around $100, should I just change that since I do not have too much mechanical aptitude (EE), an the Mercedes diagnostics is $135 ?
Any other parts I should change, other than the refrigerant.
No, do not buy the Chinese compressor that you see at EBay or Amazon for around $100.

We just replaced someone's compressor which he got from Ebay (those with blue / orange outlet plugs) and it was dead on arrival. It worked for 30 seconds, then had the problems you were describing. The control valve was bad. Buy genuine Denso.

We ordered this:

https://www.ebay.com/itm/DENSO-471-1293-New-Compressor-And-Clutch/253552790482?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

Just for reference.

You can get it cheaper maybe if you search around. It comes with oil inside (120 ml), but you need to have some PAG46 oil (8 ounce) just in case. O-ring set (the item does not come with O-rings. Change your receiver drier ($20-40) as it is probably the original, and recommended to replace the expansion valve too (costs about $20-30), 3 cans of R134a (12 ounce each from Walmart), get a vacuum pump and a manifold gauge set (the cheapo ones are about less than $100 for both).

If you are not mechanically inclined, shop around and find someone to do it for you.

I would just order the vacuum pump, refrigerant and the manifold gauge set, and measure the the pressures properly first. If you have higher pressure than 2-3 bars at the low side, with compressor running, you have a compressor issue. Trying to properly diagnose by just looking at the pressure sensor is simply inadequate.
 

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No, do not buy the Chinese compressor that you see at EBay or Amazon for around $100.

We just replaced someone's compressor which he got from Ebay (those with blue / orange outlet plugs) and it was dead on arrival. It worked for 30 seconds, then had the problems you were describing. The control valve was bad. Buy genuine Denso.

We ordered this:

https://www.ebay.com/itm/DENSO-471-1293-New-Compressor-And-Clutch/253552790482?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

Just for reference.

You can get it cheaper maybe if you search around. It comes with oil inside (120 ml), but you need to have some PAG46 oil (8 ounce) just in case. O-ring set (the item does not come with O-rings. Change your receiver drier ($20-40) as it is probably the original, and recommended to replace the expansion valve too (costs about $20-30), 3 cans of R134a (12 ounce each from Walmart), get a vacuum pump and a manifold gauge set (the cheapo ones are about less than $100 for both).

If you are not mechanically inclined, shop around and find someone to do it for you.

I would just order the vacuum pump, refrigerant and the manifold gauge set, and measure the the pressures properly first. If you have higher pressure than 2-3 bars at the low side, with compressor running, you have a compressor issue. Trying to properly diagnose by just looking at the pressure sensor is simply inadequate.
OK, I am going to get some manifold gauges and measure the High and Low pressure in the system, since its easy to do. Then at the weekend, I will add R134A with a dye to look for possible leaks, as I suspect I have one. As pointed out by mrboca and kajtek1, I should be able to confirm a bad compressor with the gauges. I will replace all of the following:

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
It comes with oil inside (120 ml), but you need to have some PAG46 oil (8 ounce) just in case. O-ring set (the item does not come with O-rings. Change your receiver drier ($20-40) as it is probably the original, and recommended to replace the expansion valve too (costs about $20-30), 3 cans of R134a (12 ounce each from Walmart), get a vacuum pump and a manifold gauge set (the cheapo ones are about less than $100 for both).
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

I am not sure where to buy the correct O rings.
Are there any other parts or tools I should buy ?
I have watched some Youtube videos on replacing the compressor.on non-Mercedes cars.
Are there any DIY articles for replacing the various AC system components which you recommend ?
 

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Let the new site settle a bit. When I do a google search fro W210 a/c compressor replacement and go to a benzworld site, it says forbidden :(. Obviously there are some bugs that need to be fixed till the new system is usable. There are some good DIY threads in the W210 for compressor / drier / expansion valve replacements under benzworld.org

In the meantime:

https://www.ebay.com/itm/A-C-System-O-Ring-and-Gasket-Kit-Santech-Industries-MT2630/202611867753?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2648

I used this for the low side of the compressor port. The above did not have what I wanted.

https://www.ebay.com/itm/A-C-O-Ring-28-X-24-mm-Santech-MT0273-013-997-44-45/362504216644?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649
 

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Let the new site settle a bit. When I do a google search fro W210 a/c compressor replacement and go to a benzworld site, it says forbidden :(. Obviously there are some bugs that need to be fixed till the new system is usable. There are some good DIY threads in the W210 for compressor / drier / expansion valve replacements under benzworld.org

In the meantime:

https://www.ebay.com/itm/A-C-System-O-Ring-and-Gasket-Kit-Santech-Industries-MT2630/202611867753?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2648

I used this for the low side of the compressor port. The above did not have what I wanted.

https://www.ebay.com/itm/A-C-O-Ring-28-X-24-mm-Santech-MT0273-013-997-44-45/362504216644?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649
I measured the pressures out of the system with manifold gauges and found the pressures to be normal(?).The High side is at 210 psi and the low side is at 45 psi.. However, I know that there is something wrong as the air conditioning is not cooling well and is intermittent. The number 7 reading sometimes stays at 6-7 and today was between 11 and 15 during the test. Car temp gauge shows 82 F.

Should I be looking at anything other than the compressor ? Should I evacuate and recharge the system or do I need to look at replacing compressor and other components ?
I will add that I did try to recharge the system in the past couple of weeks, so I am not sure if I have too much R134A in it

Thanks for your valuable guidance.
 

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I measured the pressures out of the system with manifold gauges and found the pressures to be normal(?).The High side is at 210 psi and the low side is at 45 psi.. However, I know that there is something wrong as the air conditioning is not cooling well and is intermittent. The number 7 reading sometimes stays at 6-7 and today was between 11 and 15 during the test. Car temp gauge shows 82 F.

Should I be looking at anything other than the compressor ? Should I evacuate and recharge the system or do I need to look at replacing compressor and other components ?
I will add that I did try to recharge the system in the past couple of weeks, so I am not sure if I have too much R134A in it

Thanks for your valuable guidance.
The low side pressure is high. 45 psi is 3.1 Bars which is 1 Bar higher than what it should be, based on your ambient temp. Have a look at the attached testing information (right column of graphs) where you see the plots of high side / low side pressures and refrigerant and center vent temperatures with respect to varying ambient temperatures and humidity levels based on certain test conditions depicted in the test procedures.

At 28 degrees C of ambient temp., you should have around 2 Bars of low side pressure and around 14 Bars of high pressure.

After you perform the tests per instructions (item 5 through 12 in the list) perform the test and take the measurements, and compare your results with the results in the table in the last page.

The 1 Bar higher low side pressure seems to fit into the first row if you did the tests per instructions. It tells you that the compressor has insufficient capacity.

If you have too much refrigerant (high side is 28 or more Bars if I remember correctly), the compressor will be turned off by the controller and then turned on when the pressure drops. But you will get proper cooling when the compressor runs. You should check the static pressure with your gauge at the low and high side when the engine is completely cool and NOT RUNNING. This will give you some idea about the refrigerant pressures which should be the same at low and high sides.
 

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The low side pressure is high. 45 psi is 3.1 Bars which is 1 Bar higher than what it should be, based on your ambient temp. Have a look at the attached testing information (right column of graphs) where you see the plots of high side / low side pressures and refrigerant and center vent temperatures with respect to varying ambient temperatures and humidity levels based on certain test conditions depicted in the test procedures.

At 28 degrees C of ambient temp., you should have around 2 Bars of low side pressure and around 14 Bars of high pressure.

After you perform the tests per instructions (item 5 through 12 in the list) perform the test and take the measurements, and compare your results with the results in the table in the last page.

The 1 Bar higher low side pressure seems to fit into the first row if you did the tests per instructions. It tells you that the compressor has insufficient capacity.

If you have too much refrigerant (high side is 28 or more Bars if I remember correctly), the compressor will be turned off by the controller and then turned on when the pressure drops. But you will get proper cooling when the compressor runs. You should check the static pressure with your gauge at the low and high side when the engine is completely cool and NOT RUNNING. This will give you some idea about the refrigerant pressures which should be the same at low and high sides.
Matt,

I did not have time this morning to do all the tests but I read the following with the engine off and temp at 78 on the car dial:
L -- 92 H - 80

I will do the other tests this evening, if I get back home at a reasonable time,
 

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I measured the pressures out of the system with manifold gauges and found the pressures to be normal(?).The High side is at 210 psi and the low side is at 45 psi.. However, I know that there is something wrong as the air conditioning is not cooling well and is intermittent. The number 7 reading sometimes stays at 6-7 and today was between 11 and 15 during the test. Car temp gauge shows 82 F.

Should I be looking at anything other than the compressor ? Should I evacuate and recharge the system or do I need to look at replacing compressor and other components ?
I will add that I did try to recharge the system in the past couple of weeks, so I am not sure if I have too much R134A in it

Thanks for your valuable guidance.
The trick for proper troubleshooting is to measure pressure when compressor works at max output.
That is why I advise to do the test short time after entering hot car.
You can force it to some degree by turning dials to LO on both sides, but forcing system to something that in not normal can scramble real life performance.
210 psi/45psi can be either system lowering the output, or weak compressor.
Than some replies above your report says that the system never went more than 10 bars =150 psi?
Takes proper troubleshooting to determinate the difference.
 

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Matt,

I did not have time this morning to do all the tests but I read the following with the engine off and temp at 78 on the car dial:
L -- 92 H - 80

I will do the other tests this evening, if I get back home at a reasonable time,
Just stick to the tests MB recommends... Setting LO has nothing to do with the compressor output. The compressor output is determined by the control valve, and low side pressure, which is governed by the expansion valve opening and closing. The expansion valve is designed to keep the evap. core temperature just above freezing, so it opens and closes to adjust the refrigerant evaporation. LO setting keeps the duovalves closed so there is no tempering activity, in conjunction with the blend flaps.
 

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Just stick to the tests MB recommends... Setting LO has nothing to do with the compressor output. The compressor output is determined by the control valve, and low side pressure, which is governed by the expansion valve opening and closing. The expansion valve is designed to keep the evap. core temperature just above freezing, so it opens and closes to adjust the refrigerant evaporation. LO setting keeps the duovalves closed so there is no tempering activity, in conjunction with the blend flaps.
Sorry, I should have added that the temp was set to cool to 58F and I did clean the duo-valves past weekend. Will do the rest of the tests tonight.
 

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Close enough.. The reason why the LO LO is selected for the first row is to make sure that the temperature readings from the center air vents can be measured reliably. and consistently (without tempering)
 

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Matt , I am trying to understand this document while converting BAR to PSI and F to C.
If I get it right then at 25C, according to the first diagram the Lo and Hi should be very similar at around 70 psi. Mine is at approx 48 PSI Lo and 250 on Hi side -- compressor is bad ?
For the other conditions I see similar readings, perhaps the Hi side is a little lower.
Interpreting the reason for any of these is rather cryptic form the document.

Right now,I am not sure if any or all the components mentioned ( compressor, expansion valve or blocked hose ) are culprits. I know for sure that there is refrigerant in the system, but perhaps not the optimum amount -- too much or too little.Not sure how a hose can get blocked, but since the error code is there for it , there must be a way.
 

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First you need to know how to convert psi (Pound per Square inch) to Bars. 1 Bar = 14.5 psi. So if you are reading 48 psi at the low side, it is 48/14.5 = 3.3 Bars. 250 psi at the high side is 250/14.5 = 17.2 Bars.

This is what you tell me what you read with your gauges.

Now find the graphs for the 210.055 chassis (this is 1997 E320 which has the same a/c system as your car) which are the right column of graphs. Then if the ambient temperature is 25 degrees C, find 25 degrees C in the horizontal line (x or abscissa plane), and draw a vertical line over all 4 graphs, and note the values in the vertical lines.

I read

4-6 degrees C for the air temp from the center vent
1.8 Bars for the low side pressure
10-14 Bars of High side pressure
94 degrees C for the refrigerant temperature.

So if you are reading 3.3 Bars at the low side, it is 3.3 - 1.8 = 1.5 Bars higher than what it should be. 1.8 Bars is around 26 psi, and you are reading 48 psi.

So you have a high low pressure side problem. If you look at the interpretations, it could be a bad compressor, or a continuously open expansion valve. For the latter, you get ice cold air coming from the vents first, then it will get warmer and warmer, as the low side pressure starts building up. Sometimes a defective expansion valve will cause the compressor valve to go bad, as when you have more refrigerant in the liquid form at the low side, and the compressors do not like to compress refrigerants in liquid form.

Regarding the line blockage, over time, you get crud in the system, especially if you introduce moisture, air when you charge the system up (without purging the charge hoses of moist air). With refrigerant, oil and water and other contaminants, you will have a plugged up receiver / drier and partially clogged condenser. This will increase the high side pressure, as the flow is restricted. This is one of the problems of relying on the pressure gauge of the climate control system which reads the pressure after the drier, not before. So if the drier is plugged up and restricting flow, the gauge will always read less pressure than the actual gauge pressure at the high side valve. This is why it is important to use gauges, instead of completely relying on climate control system readings.
 
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