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Discussion Starter #41
Kajtek1,
I have seen your posts and replies. I have always respected how you and Mrboca have tried to guide me with:
However, looking at the one below, you are clearly losing patience and I am doing my best to follow your guidance:

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I takes 60 seconds in the morning and 60 seconds in the afternoon restart and post the numbers to troubleshoot the system for 90% of the problems and sometimes additional 2 minutes to follow up on compressor performance. .
So all it takes is about 3-5 replies to have good results when one follows the procedure.
Now here, we are on reply 37 and we still lack troubleshooting data.
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I have posted the values at least a couple of times. I have posted abbreviated values to just provide the information that I deduced was critical, so as not to make a long post. I can continue posting values but that would cause the replies to go well over 37!

I am still not sure what is meant by: to follow up on compressor performance. .

Anyway, I really do appreciate your time and I certainly do not want to waste any of it or make you more upset. Hence I suggested getting it to someone who can look at it physically -- that is not my first course of action, but its meant to keep things sane on this site and prevent senior members from being upset.
 

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I am one of the most patient man in the World. Trust me on this one ;)
However I don't know how make you follow the procedure.
It took almost 2 pages of replies to comply with reply #3, now another advising request about observing refrigerant pressure got lost.
That would be reading comprehension I guess, but I am far away from being English teacher.
So once again, give us the info I requested in reply #30 and maybe we will get somewhere?
 

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Discussion Starter #43
10 bars on working AC is low pressure.
To follow up on hot test, when you come in hot afternoon, turn ignition on, display #7 refrigerant pressure, start the engine and observe the pressure change for next couple of minutes while driving.
Your sensors when cold show 14 degrees difference. A bit extreme, so maybe the car wasn't completely cold? Try to repeat that?

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Ok, I think you are asking me to do the following:
On a hot day, like today in Milpitas: I will read item 7 on from the onboard diagnostics.
(with the AC turned LO, LO) I will observe #7 while driving for the next 2-5 minutes and post the results.

Do I have it correct?

Yes, I was educated in England, so perhaps the English English is a little different from the American English -- my US-born kids tell me that all the time.
 

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You've got it.
I don't like the LO- LO idea since that is not natural situation how the car works.
When I have my thermostats set to 75F and I enter the interior with 130F, the AC goes to max for few minutes regardless.
Funny, back in Poland I had English, English teachers, but being that my 3rd language I am not pretending to be good in it ;)
Would that make my American English the 4th language?
 

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Discussion Starter #45
I read the following: The thermostat was set to 72 F.

At start, #7 was at 06 it continued to go higher until it reached 15. Then it went down to 09 and then it went between 09 and 15, continuing to go up and down.
 

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I read the following: The thermostat was set to 72 F.

At start, #7 was at 06 it continued to go higher until it reached 15. Then it went down to 09 and then it went between 09 and 15, continuing to go up and down.

After dropping my daughter to work this morning (she had a flat battery for some reason), I checked #7 and it was changing between 8 and 14 with temperatures set to 72, and the a/c was ice cold.
 

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Discussion Starter #48
With a hot car( driven for 15 miles, outside at 77, the #7 varied between 07 and 09.
I did charge the system yesterday and some of the Freon must have gone into the systems, based on remaining "feel" of the can. The can of refrigerant did become very cold when filling, so I think that's a good sign.
The gauge on the AC Pro fill mechanism might be incorrect since it stayed at the same point in the green zone -> 48 psi. The green range on this gauge goes from 30 to 50 psi.
Anyway, the AC was cooling at this pressure.
My car is an E320 Model year 2000 if it makes a difference.
 

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I don't use the can gauge, but per my observation when you open the valve, it will show can pressure, where 48 psi is about right.
I think it will show you car AC pressure when you turn the valve off, but again, that is educated guess.
Good to hear your system cools now.
It is not freon btw.
 

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You mean you got #7 between 07 and 09 AFTER you charged (or tried to charge) the system ? With outside temp 77 and internal setting 72 you will get to that temperature very soon especially when the humidify is low. Then the climate controller will start blending warm air and cool air. In FL when outside is almost 93 and you set the target temp to 72, the climate control is always in cooling mode (no blending). My son used to set the temps to LO LO hoping that it will cool faster. The fact is regardless you set it to LO LO or 72 72 when it is hot outside, there is absolutely NO difference how the a/c works. It will try to cool as much it can. The same goes for the home air conditioners. Just because you set the temp to 60 when inside temp is 80, it will not cool any faster rate than if you set the a/c to 70 :)

When you connect the can with gauge without pressing the trigger to release gas, and with the ignition off. It will read the low side pressure and it should be in the red zone. (75 to 80 psi depending on the ambient temp).



If you start the engine and the a/c, after few minutes, the pressure should be around 30 psi with the trigger not pressed. When you press the trigger to charge you will see slight increase in the pressure to show the system is charging. When you let the trigger go and wait 10 seconds to stabilize, it will show the new pressure.

Read the link from the AC Pro :)

How to Diagnose Your Car?s Air Conditioner Using A/C Pro - AC Pro<?php/* bloginfo('name'); */?>

It is interesting that the link or the video does not talk about purging the air of AC Pro long hose. Without doing so, you introduce moisture and air into the system.
 

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That's not exactly true. This applies to cars not houses, but the lower you set the temp, the faster the car will cool down. The fan is going to stay at a higher speed for a longer amount of time to try and cool the car down as fast as possible. So setting a lower temp will cool the car down faster although it won't have any affect on compressor output.
 

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So you are saying, with inside ambient temp is 90, the temp setting at LO LO will cause the controller to set the blower at a higher capacity, compared to 72 72 setting ?

If so,and I set the temp to 72 72 and increase the blower speed, the car will be cooler faster ?

And do I really care about the air temperature at the rear of the cabin, if I am the only passenger ?

The evaporator has limited capacity of cooling, so if the airflow is less, you will have cooler airflow, than a higher volume of air flow with blower at the highest setting.

The easiest way to get cooler air faster is to set the air to recirculate.
 

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You guys are ignoring the fact that system is controlled by computer and we don't know the exact computer program.
The AC will go to max even when you set it to 90F and cabin temperature is 100.
My only complain about the program is that it does not gradually change the output, but it high or nothing.
That gets annoying especially in heating when warming up the car the system will blow very hot air even when cabin is already warm, only to abruptly cut it when set temp is reached.
Bottom line, how do you know the computer is not switching to recirculate for you?
 

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"So you are saying, with inside ambient temp is 90, the temp setting at LO LO will cause the controller to set the blower at a higher capacity, compared to 72 72 setting ?"

Not capacity but fan speed. Let's ignore LO LO for now because the fan will stay at max speed no matter what. Let's say 57 57 vs 72 72 instead. When you first turn it on yes for both 57 or 72 the fan will be at max. But if inside ambient temp is 90 and you set the desired temp at 72, the fan speed will gradually slow down much sooner versus when the desired temp is set at 57.

"If so,and I set the temp to 72 72 and increase the blower speed, the car will be cooler faster ?"

I'm assuming you have the fan on manual control right? My comment is based on Auto fan speed. If you are talking about manual fan speed, then desired temp has no affect on cooling rate unless the desired temp is close to inside ambient temp.

"And do I really care about the air temperature at the rear of the cabin, if I am the only passenger ?"

That's up to you I guess. I like leaving the vents for the rear open because I want as much hot air removed as quickly as possible.

"The evaporator has limited capacity of cooling, so if the airflow is less, you will have cooler airflow, than a higher volume of air flow with blower at the highest setting."

I don't believe this. Evaporator capacity is engineered for this specific car. Otherwise we could just use any evaporator from any car we want (ignoring fittings and space requirements). I don't think Mercedes or any manufacturer would use an evaporator that has a capacity too small for the application. In general terms the evaporator will never be able to keep up with maximum cooling of all hot air outside because the surface area is too small. But the evaporator does not need to cool down all the hot air outside. It only has to cool the cabin down to the desired temp. Capacity to cool the cabin is sufficient. Evaporator capacity to cool all hot air outside is impossible. But air temp coming out of the vents is also dependent on many other variables like refrigerant level, compressor efficiency, condenser air flow, etc. So this is not really relevant to the discussion.

Now the amount of cool air coming out from the vents (assuming LO LO) is going to be dependent on intake air temp going to the evaporator. If intake air temp is 95 the air coming out of the evaporator going the the vents is not going to be as cold as possible. The air from the vents will only be in the 50's give or take. But that is still enough to cool the cabin. Now if intake air temp is 75, then the vent temperature will be in the high 30s low 40s because the evaporator does not have to remove as much heat from the air.

"The easiest way to get cooler air faster is to set the air to recirculate."

Yes that's true. But the controller already does that for you. You can actually feel and hear when the intake switches from recirculate to outside air. In recirculate the center vents get the maximum amount of airflow while the side vents get some airflow. In fresh air mode the side vents get max air flow and the center vents get some air flow.
 

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You guys are ignoring the fact that system is controlled by computer and we don't know the exact computer program.
The AC will go to max even when you set it to 90F and cabin temperature is 100.
My only complain about the program is that it does not gradually change the output, but it high or nothing.
That gets annoying especially in heating when warming up the car the system will blow very hot air even when cabin is already warm, only to abruptly cut it when set temp is reached.
Bottom line, how do you know the computer is not switching to recirculate for you?
The controller will set the fan to max speed in your situation because it will ignore the factory programming to automatically adjust fan speed based on the different variables. Setting the temp at 90 (HI) is the same as setting it to LO. Fan speed will be max regardless of outside or inside temperature.

And yes I completely agree with you regarding the gradual change in output. This is the only car I have been in with automatic climate control that will not change vent temperature based on the desired temp that you set. Other cars will change the vent temperature based on the desired temp that you set. The programming of the controller is very weird. I will also say, that I don't understand why the controller will never go below 3 fan speed in automatic fan mode. Another strange decision by Mercedes that is actually very annoying.

And yes the computer does switch to recirculate for you. See my reply above. You can identify when it's in recirculate and fresh air mode by feel and sound.
 

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Not capacity but fan speed. Let's ignore LO LO for now because the fan will stay at max speed no matter what. Let's say 57 57 vs 72 72 instead. When you first turn it on yes for both 57 or 72 the fan will be at max. But if inside ambient temp is 90 and you set the desired temp at 72, the fan speed will gradually slow down much sooner versus when the desired temp is set at 57.
The airflow capacity (Cubic foot per minute (CFM) is a function of fan speed, so we are talking about the same thing, though may not be a linear functional relationship. So you do agree when start up LO LO and setting of 72 72 when the ambient is 90 will be at max. That was the point.


"If so,and I set the temp to 72 72 and increase the blower speed, the car will be cooler faster ?"

I'm assuming you have the fan on manual control right? My comment is based on Auto fan speed. If you are talking about manual fan speed, then desired temp has no affect on cooling rate unless the desired temp is close to inside ambient temp.
Yes, I use manual mode more or less, always, as I do not think the AUTO mode is as clever as some people think. The AUTO program does not meet my requirements of cooling. To get maximum cooling I set the recirculate mode immediately (which should really be default setting, or at least it should not reset to outside air after the car is switched off. I set the blower settings and the airflow direction to my own requirements at that point rather than someone's algorithm of what it should be. My LS430 has a wonderful climate control as it has more control on the airflow issues, and more precise control of temperature settings. The AUTO mode also controls the airflow path control, but the tempering or blending function to set the temperature at certain level is common to both manual and auto mode..

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"The evaporator has limited capacity of cooling, so if the airflow is less, you will have cooler airflow, than a higher volume of air flow with blower at the highest setting."

I don't believe this. Evaporator capacity is engineered for this specific car. Otherwise we could just use any evaporator from any car we want (ignoring fittings and space requirements). I don't think Mercedes or any manufacturer would use an evaporator that has a capacity too small for the application. In general terms the evaporator will never be able to keep up with maximum cooling of all hot air outside because the surface area is too small. But the evaporator does not need to cool down all the hot air outside. It only has to cool the cabin down to the desired temp. Capacity to cool the cabin is sufficient. Evaporator capacity to cool all hot air outside is impossible. But air temp coming out of the vents is also dependent on many other variables like refrigerant level, compressor efficiency, condenser air flow, etc. So this is not really relevant to the discussion.

Now the amount of cool air coming out from the vents (assuming LO LO) is going to be dependent on intake air temp going to the evaporator. If intake air temp is 95 the air coming out of the evaporator going the the vents is not going to be as cold as possible. The air from the vents will only be in the 50's give or take. But that is still enough to cool the cabin. Now if intake air temp is 75, then the vent temperature will be in the high 30s low 40s because the evaporator does not have to remove as much heat from the air.
Your last paragraph is the limitation of the evaporator I was talking about. On the way back from dinner while parked, I checked the evap core temperature, it was around 34 to 36 Fahrenheit with blower in lowish speed. I increased the blower speed to max, and the evap temp went up to 46 to 48. Outside air was 88.

"The easiest way to get cooler air faster is to set the air to recirculate."

Yes that's true. But the controller already does that for you. You can actually feel and hear when the intake switches from recirculate to outside air. In recirculate the center vents get the maximum amount of airflow while the side vents get some airflow. In fresh air mode the side vents get max air flow and the center vents get some air flow..
This is exactly why I do not use AUTO mode much. In South FL you get hot and outside air, and the controller my car has does not have any idea what the humidity level is (no humidistat), so after a while it switches to outside air which makes the a/c work harder to drop the temperature due to dew point level. With the blower blowing at max, you get cool and wet air, as the moisture in the air will not have a chance to completely condense on the evaporator core. If you set the airflow to recirculate manually, the moisture in the cabin air will be removed faster, and this will get the cabin air cool faster.
 
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