AC Serviced - Final Steps - PeachParts Mercedes-Benz Forum

nyko46 · #1 06-13-2011, 07:47 PM

Dear Friends:
For the first time I completed this Sunday to flush the whole AC system from my 1982 300SD. As I also found leakage in the compressor body I had it replaced for a new (not rebuilt) compressor. With the system completely clean I installed new expansion valve, new receiver and all new O-rings and finally vacuumed and checked for leakage of vacuum and no leaks showed in the vacuum gauge. After everything in place I started to add new oil in the following way:
The compressor came with an amount of oil, which I don't know how much.
I then added 6 Fluid OZ in the suction line considering that the whole system was evacuated and was completely empty. After oil added into the system I started to add new 134a as following: Connecting the high and low pressure gauges I used the 12 Fluid OZ can until the clutch engaged. From there I added one more can with attention in the pressure and the sight glass in the receiver for bubbles. When second can was empty, the low pressure gauge was showing 55 PSI and the high gauge was showing 300 PSI. The ambient temperature at that time was around 88 F.
With the engine running around 2000 RPM the new compressor got hot and with a grinding noise but I let it run for about 25 to 35 minutes only.
The condenser cooling fan kicked on and stay on for the same length of the time as the engine in my garage.
Today I just try to run when coming back from work but as I was not sure about the quantity of oil and refrigerant added to the system and with the compressor noise present, I turned it off and decided to get help from people in this site that knows better about Mercedes AC.
The system is cooling the air but not much as any other car. In other words, it is just cooling the air but not bringing it to a cold as a good AC system.
Please give me your help regarding oil and refrigerant quantities and also about the high and low pressure in the gauges. About compressor noise also will be helpful to know.
Thanks everyone.

Nyko46

nyko46 · #2 06-13-2011, 07:57 PM

Dear Friends:
For the first time I completed this Sunday to flush the whole AC system from my 1982 300SD. As I also found leakage in the compressor body I had it replaced for a new (not rebuilt) compressor. With the system completely clean I installed new expansion valve, new receiver and all new O-rings and finally vacuumed and checked for leakage of vacuum and no leaks showed in the vacuum gauge. After everything in place I started to add new oil in the following way:
The compressor came with an amount of oil, which I don't know how much.
I then added 6 Fluid OZ in the suction line considering that the whole system was evacuated and was completely empty. After oil added into the system I started to add new 134a as following: Connecting the high and low pressure gauges I used the 12 Fluid OZ can until the clutch engaged. From there I added one more can with attention in the pressure and the sight glass in the receiver for bubbles. When second can was empty, the low pressure gauge was showing 55 PSI and the high gauge was showing 300 PSI. The ambient temperature at that time was around 88 F.
With the engine running around 2000 RPM the new compressor got hot and with a grinding noise but I let it run for about 25 to 35 minutes only.
The condenser cooling fan kicked on and stay on for the same length of the time as the engine in my garage.
Today I just try to run when coming back from work but as I was not sure about the quantity of oil and refrigerant added to the system and with the compressor noise present, I turned it off and decided to get help from people in this site that knows better about Mercedes AC.
The system is cooling the air but not much as any other car. In other words, it is just cooling the air but not bringing it to a cold as a good AC system.
Please give me your help regarding oil and refrigerant quantities and also about the high and low pressure in the gauges. About compressor noise also will be helpful to know.
Thanks everyone.

Nyko46

engatwork · #3 06-13-2011, 08:19 PM

I hate to break it to you but it is probably performing about as good as it can on r134 if the evap is original (dirty). Unfortunately, these cars don't convert well. You can't really go by the site glass. There are many post on here regarding a/c and the issues of converting one to 134.

nyko46 · #4 06-13-2011, 08:37 PM

Quote:

Originally Posted by engatwork

I hate to break it to you but it is probably performing about as good as it can on r134 if the evap is original (dirty). Unfortunately, these cars don't convert well. You can't really go by the site glass. There are many post on here regarding a/c and the issues of converting one to 134.

You mean that this car AC system will not perform well using 134a?
My evaporator was very well cleaned using AC flushing fluid.
What can you tell me about the compressor noise?

leathermang · #5 06-13-2011, 08:57 PM

Jim was referring to the outside of the evaporator... the part the air is in contact with... not the inside which would use flush to clean... but the fins you would use some mild detergent or soap on and then flush with water out the drain hole...

134a is by definition about 20 percent less efficient that R12.

It is normal to put that oil into different parts of the system as you put it back together...rather than all in on place...

Did you put in New receiver - dryer ?

engatwork · #6 06-13-2011, 08:57 PM

Won't perform worth a flip on r134. The clean evaporator I am referring to is the fins. The only way to clean it is to actually replace it. Your loading your compressor up is the reason it is noisy.

rscurtis · #7 06-13-2011, 09:01 PM

R4 compressors make some noise under load. Converting back to R12 will enhance your cooling (espescially in Texas!) and lower the high side pressure in the system. I added 6 OZ to my '83 300D several days ago (first time in 4 yrs.), and with an ambient temperature of 92* and a dew point of 73, I could still get 38* at the center vents. Depending on which oil you used, you may have to completely flush the system again.

nyko46 · #8 06-13-2011, 09:02 PM

Quote:

Originally Posted by leathermang

Jim was referring to the outside of the evaporator... the part the air is in contact with... not the inside which would use flush to clean... but the fins you would use some mild detergent or soap on and then flush with water out the drain hole...

134a is by definition about 20 percent less efficient that R12.

It is normal to put that oil into different parts of the system as you put it back together...rather than all in on place...

Did you put in New receiver - dryer ?

Yes, I did put a new receiver - dryer and also new expantion valve.
Mine was all clogged and the dryer also had a very dirty oil in it.

nyko46 · #9 06-13-2011, 09:08 PM

Quote:

Originally Posted by rscurtis

R4 compressors make some noise under load. Converting back to R12 will enhance your cooling (espescially in Texas!) and lower the high side pressure in the system. I added 6 OZ to my '83 300D several days ago (first time in 4 yrs.), and with an ambient temperature of 92* and a dew point of 73, I could still get 38* at the center vents. Depending on which oil you used, you may have to completely flush the system again.

The oil used was AC/PRO PAG 150 and the refrigerant was the regular cans with 12 OZ.
Do you think that I have enogh oil in the system or not?

nyko46 · #10 06-13-2011, 09:10 PM

Quote:

Originally Posted by rscurtis

R4 compressors make some noise under load. Converting back to R12 will enhance your cooling (espescially in Texas!) and lower the high side pressure in the system. I added 6 OZ to my '83 300D several days ago (first time in 4 yrs.), and with an ambient temperature of 92* and a dew point of 73, I could still get 38* at the center vents. Depending on which oil you used, you may have to completely flush the system again.

I did not measure temperature inside the car but I am sure that it was around 70s

nyko46 · #11 06-13-2011, 09:13 PM

Quote:

Originally Posted by nyko46

Yes, I did put a new receiver - dryer and also new expantion valve.
Mine was all clogged and the dryer also had a very dirty oil in it.

Do you beleive that the noisy compressor is because it is new and need a breakdown?

nyko46 · #12 06-13-2011, 09:16 PM

Quote:

Originally Posted by engatwork

Won't perform worth a flip on r134. The clean evaporator I am referring to is the fins. The only way to clean it is to actually replace it. Your loading your compressor up is the reason it is noisy.

In the "Your Loading Compressor" are you reffering as too much or too low oil / refrigerant?

leathermang · #13 06-13-2011, 09:22 PM

About a week ago when we were talking I asked you if you had read the sticky at the top of the page...
And if you had any other specific questions... You said not at that time...
It appears you went ahead without asking any more questions of anyone... and made some major mistakes as a result...
You may have to start over on large parts of what you have done .
I hope you have not started on your other MB yet...

nyko46 · #14 06-13-2011, 09:34 PM

Quote:

Originally Posted by leathermang

About a week ago when we were talking I asked you if you had read the sticky at the top of the page...
And if you had any other specific questions... You said not at that time...
It appears you went ahead without asking any more questions of anyone... and made some major mistakes as a result...
You may have to start over on large parts of what you have done .
I hope you have not started on your other MB yet...

So what is the to do at this stage?
Do you think that I have oil and refrigerant sufficient to not damage the new compressor?

leathermang · #15 06-13-2011, 09:52 PM

My personal opinion is that you put all the oil into the wrong place...and that may have messed up the compressor... either by having too much in it... or it being too far away to get mixed with the refrigerant so as to provide the lubrication it needs.... either one could be deadly to the compressor..
The only way to tell how much oil you have is to take the system apart , flush, and measure it back in... and of course the suggestion is to put it spread around in several places..
The R4 compressor does not have an oil sump.. thus the mixing of the oil in the refrigerant becomes very important ... way more than other type compressor which do have a reserve of oil to keep them going in the event of refrigerant loss...