AC NOT COOLING - 1982 300-SD - PeachParts Mercedes-Benz Forum

nyko46 · #1 06-18-2011, 12:26 PM

I still not knowing why on my 1982 - SD AC still not working.
I changed compressor, expansion valve, receiver, flushed system completely section by section. Mounted everything as per MB manual and it still not working. System has compression and vacuum as any other AC system.
As condenser was heating too much and not cooled air coming from evaporator, yesterday I had the system evacuated again assuming that there was too much oil. I had it assembled again not adding extra oil to it.
Put around 400 g (14 oz)of 134 a and tested but there are not cooled air coming from vents and suction hoses are not even cool. A person who works in a company that make AC compressors for cars took measurements of temperature coming and leaving condenser and also from evaporator to compressor said that there was too much oil not allowing refrigerant to cool down and pushing gas to drier instead fluid. We the opened the system removing oil and flushing it again. We vacuumed the system again and add refrigerant to it but it did not made any difference.
I am somewhat frustrated spending money in new parts, refrigerant, and time and to have the system not cooling at all.
What had I missed or where is the problem located?
Thanks everyone.
Nyko46

leathermang · #2 06-18-2011, 01:45 PM

Typically the charge with R134a would be ( by weight ) 80 percent of the capacity the system used for R12....

Many of our systems use about 32 plus oz....
so there is the possibility that you simply have not put enough refrigerant into your system.... if that 14 oz measurement was correct...
but I am concerned by the seemingly mismashed haphazard way your system is being approached... Do you really have good help up there ?
If is not usual to be making those temperature measurements at those places in the system... sure, if you have the correct tools... etc..
but typically you would only be measuring the center vent temp with a pencil thermometer to confirm the pressure readings you are getting on your gauges as you charge with refrigerant... all those measurements and amounts with no reference to the system high and low side pressures ?
Something does not feel right about the situation.. this is about the third time you have posted a new thread for this job.. in between you consult and act using local help... but do no answer the questions.... and it does not seem like you follow the suggests we give you... then you come back and wonder why your ac is not working.... If I could figure out where the gap exists which is causing your problem I would try to help you fix it... as I have tried in the past... but from your descriptions so far.. which also sound like you now have no oil in the system... didn't you previously add all your oil in one place ?
Unless you become a little more orderly in your attack on your system... it is hard to diagnose and help you...

nyko46 · #3 06-18-2011, 02:11 PM

Quote:

Originally Posted by leathermang

Typically the charge with R134a would be ( by weight ) 80 percent of the capacity the system used for R12....

Many of our systems use about 32 plus oz....
so there is the possibility that you simply have not put enough refrigerant into your system.... if that 14 oz measurement was correct...
but I am concerned by the seemingly mismashed haphazard way your system is being approached... Do you really have good help up there ?
If is not usual to be making those temperature measurements at those places in the system... sure, if you have the correct tools... etc..
but typically you would only be measuring the center vent temp with a pencil thermometer to confirm the pressure readings you are getting on your gauges as you charge with refrigerant... all those measurements and amounts with no reference to the system high and low side pressures ?
Something does not feel right about the situation.. this is about the third time you have posted a new thread for this job.. in between you consult and act using local help... but do no answer the questions.... and it does not seem like you follow the suggests we give you... then you come back and wonder why your ac is not working.... If I could figure out where the gap exists which is causing your problem I would try to help you fix it... as I have tried in the past... but from your descriptions so far.. which also sound like you now have no oil in the system... didn't you previously add all your oil in one place ?
Unless you become a little more orderly in your attack on your system... it is hard to diagnose and help you...

I had in the past days charged refrigerant in the the system with 28 oz and the low side went to 80 PSI at 2000 RPM and the high side to 350 PSI.
Mercedes manual ask for 177 cc (5.98 oz) of oil in the compressor alone and a total amount of 300 cc (11.15 oz) total in the whole system with new compressor and system flushed.
Even following this numbers it still not working.

leathermang · #4 06-18-2011, 02:22 PM

Can you show us where that reference for a total of 17 oz of oil is ?
That is two and close to three times what I have seen most systems call for....but it could be right.. but with your local help blaming the amount of oil ... you need to find out for sure ...
And on this last insertion of oil... did you place it around the system like we talked about last time ?

Tell us about the conditions of the testing...
Are your windows up or down ?
do you have a good fan blowing into the condensor when running at 2000 rpm ?
Do you have the AC on FULL MAX but the blower on low ?
Are you using a $5 pencil thermometer in the center vent when charging ?

nyko46 · #5 06-18-2011, 02:35 PM

Quote:

Originally Posted by leathermang

Can you show us where that reference for a total of 17 oz of oil is ?
That is two and close to three times what I have seen most systems call for....but it could be right.. but with your local help blaming the amount of oil ... you need to find out for sure ...
And on this last insertion of oil... did you place it around the system like we talked about last time ?

Tell us about the conditions of the testing...
Are your windows up or down ?
do you have a good fan blowing into the condensor when running at 2000 rpm ?
Do you have the AC on FULL MAX but the blower on low ?
Are you using a $5 pencil thermometer in the center vent when charging ?

Oil was placed all around the system.
Windows are closed, Blower tryied in high and low speeds.
Not sure if copy from Mercedes Manual is attached.

leathermang · #6 06-18-2011, 02:49 PM

Windows should be OPEN.
Blower should be on low speed.
It can not be placed all around the system... you put it certain places... How much oil did you put into it this last time ?
Do you have a pencil type thermometer to put into the center vent or not ?
How much refrigerant did you put in this last time ?
If you do not start reading and answering EACH of my questions from the previous post I am going to go play elsewhere...
I do not mind trying to help you ... but I am not a masochist ... work with me or I will give up.

nyko46 · #7 06-19-2011, 01:36 PM

Quote:

Originally Posted by leathermang

Windows should be OPEN.
Blower should be on low speed.
It can not be placed all around the system... you put it certain places... How much oil did you put into it this last time ?
Do you have a pencil type thermometer to put into the center vent or not ?
How much refrigerant did you put in this last time ?
If you do not start reading and answering EACH of my questions from the previous post I am going to go play elsewhere...
I do not mind trying to help you ... but I am not a masochist ... work with me or I will give up.

Hei fellow:
What can you say about conversion from R12 to 134a?
Since Mercedes 1982 was designed to run with R12, wil the AC system working with 134a perform the same as R12 ?
Can not be this the reason why mine is not cooling?
If you are father, happy father's day.

Nyko46

leathermang · #8 06-19-2011, 01:39 PM

Yes , that can be the cause of your lack of good cooling.

vstech · #9 06-19-2011, 02:26 PM

Quote:

Originally Posted by nyko46

Hei fellow:
What can you say about conversion from R12 to 134a?
Since Mercedes 1982 was designed to run with R12, wil the AC system working with 134a perform the same as R12 ?
Can not be this the reason why mine is not cooling?
If you are father, happy father's day.

Nyko46

yes, that can cause poor cooling under high temps, but you are not getting ANY cooling, it's due to poor assembly, and installation and charging and oiling of the parts you have.

nyko46 · #10 06-19-2011, 05:43 PM

Quote:

Originally Posted by vstech

yes, that can cause poor cooling under high temps, but you are not getting ANY cooling, it's due to poor assembly, and installation and charging and oiling of the parts you have.

Guys:
I have read all the posts regarding my issue with this AC not cooling.
All of then have good instructions and very good teachings.
I am convinced that I will need to remove all the parts again, flush and recharge my system again. Before go ahead and waste time and money one more time, please send me the quantities of : OIL, 134a that this system must have considering that the car was built to use R12 and the entire system will be emptied and cleaned.
Thanks.

Nyko46

leathermang · #11 06-19-2011, 07:11 PM

If you empty the entire system you should put R12 into it...You live in TEXAS.... if you lived up north R134a might work fine... unless your system is perfect and possibly upgraded to PFlow condensor with high performance aux fan you are fighting a losing battle with R134a. I am in Texas also... it is close to 106 outside... just too hot to lose 20 percent efficiency with the other refrigerant and think you can be cool.

nyko46 · #12 06-19-2011, 07:51 PM

Quote:

Originally Posted by leathermang

If you empty the entire system you should put R12 into it...You live in TEXAS.... if you lived up north R134a might work fine... unless your system is perfect and possibly upgraded to PFlow condensor with high performance aux fan you are fighting a losing battle with R134a. I am in Texas also... it is close to 106 outside... just too hot to lose 20 percent efficiency with the other refrigerant and think you can be cool.

Please, tell me the quantities of oil and, in this case for the suggested R12.
Does your car use 134a or R12?
In my case I am sure that after condenser, the receiver IS NOT receiving the compressed gas in form of fluid as supposed and after receiver the same compressed gas is reaching the expansion valve and automaticaly not expanding fluid because gas is going there instead fluid.
How come many cars are converted to 134a and it work very fine?
Is Mercedes an exception?

tyl604 · #13 06-19-2011, 08:00 PM

Generally speaking people are not satisfied with a conversion because they do not get the normal amount of cooling they received with R12. I agree that you should go back to R12 and not use the R134a.

nyko46 · #14 06-19-2011, 08:37 PM

Quote:

Originally Posted by tyl604

Generally speaking people are not satisfied with a conversion because they do not get the normal amount of cooling they received with R12. I agree that you should go back to R12 and not use the R134a.

No satisfaction with 134 for less cooling than R12 make sense but my situation is NO cooling at all.
As I posted before I installed brand new parts and positive that was installed correctly. There is not way to install an expansion valve in wrong direction because the threads are different not giving chance to be installed wrongly.
My system was flushed properly, there are no leaks and compressor is making suction and compression.
As previously mentioned, after the condenser was supposed receiver to receive that compressed gas in form of fluid but is IS NOT happening.
Evaporator will work properly when receiving fluid and not gases.
Why?

Nyko46

vstech · #15 06-19-2011, 10:45 PM

ok.
if you want us to help you, you are going to have to provide specific information.
where did you put the oil in the system.
how much oil is in the system.
how much refrigerant is in the system?
what type of oil specifically is in the system now.
if it's got pag in it, you cannot change back to 12 unless you replace the compressor.

14 oz 134 is not enough. 17 oz oil is too much.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode