1983 300sd AC compressor question - PeachParts Mercedes-Benz Forum

Mrman7627 · #1 07-11-2015, 09:23 PM

Hello I recently have been trying to repair my ac system i was told the compressor worked. I replaced the expansion valve the receiver dryer flushed the system out dried the system out and replaced all the o rings. I refilled the system with oil and freon and it seems to be holding the charge and now when i start the car and turn on the ac it starts which it didnt before cause of the leak it had but the compressor spins then stops and stutters for a second then spins for awhile again and it or the belt squeals when it stutters. Does this mean that the compressor needs more oil? and if so should i completely remove the compressor get good oil for it put it in the compressor put it back together and put more freon in it or is that too much effort if im not buying a new one? can i just add a can of oil to the system like i did when i put more freon in it? any advice would be greatly appreciated. Also i cant seem to find out exactly how much psi the system should have on the "low side? part where you add more freon" and if i have to test it when its on or off. Thanks for all the help thus far!!!!

engatwork · #2 07-12-2015, 07:02 AM

Sounds like you don't have the proper freon charge to me. My suggestion would be to take everything apart, flush everything out good, install a new dryer, add the proper amount of refrigerant oil, vacuum for a few hours and re-charge with the proper amount.

vstech · #3 07-12-2015, 07:08 AM

did you evacuate the system before adding freon?

It sounds like you put in the correct amount of oil... perhaps the compressor is done...

Mrman7627 · #4 07-12-2015, 09:34 AM

I used one cqan of oil rec harge and i only used 1 can of 6oz 134a freon which it said was equivelant to one pound i believe my system takes just over two pounds of refrigerent the reason i used 134a was because it was retrofitted with a 134a attachement so i assumed thats what was in the system the psi reader that i used to put the pressure in says its high "80 psi" but that was only with one can of freon one can of oil shot and one can of stop leak so it seems like that reading couldnt be right as there would only be 1 pound of freon in it. i also cant find my manual currently and im having a hard time finding out what the psi reading on the side you put the freon in should be. Thanks for the tips so even though i just replaced the reciever drier i should do so again?

vstech · #5 07-12-2015, 09:52 AM

Psi I'd dependant on both outside and cabin temp... Also airflow, compressor speed, condenser cleanliness, airflow inside and out...

vstech · #6 07-12-2015, 09:54 AM

Are you sure you used 134a? 6 oz equaling a pound sounds like E'S 12 or 12a... propane...

ROLLGUY · #7 07-12-2015, 10:44 AM

Did you leak test the system? Chances are if the system was empty when you got it, there was a leak. It is most important to check for leaks before charging a system, so you won't be charging it again any time soon. You say you replaced all the Orings, did you put a little oil on each one? You say you flushed the system, did you flush the compressor too? (I hope not!). I believe your car takes about 2.2 pounds of R12, so 134a should be about 80-85% of that.....Rich

ROLLGUY · #8 07-12-2015, 10:46 AM

Quote:

Originally Posted by vstech

Are you sure you used 134a? 6 oz equaling a pound sounds like E'S 12 or 12a... propane...

It looks like a typo (6oz should be 16oz). "I used one cqan of oil rec harge and i only used 1 can of 6oz 134a freon which it said was equivelant to one pound "

Mrman7627 · #9 07-12-2015, 02:15 PM

Yes it was a typo yes I flushed the system out but not the compresdor I detached all lines and flushed them let the cleaner sit then used an air compressor to shoot through the pipes until not a drop of anything was coming out if them I then oiled and replaced all the o rings I don't think the system leaks cause there is cool air blowing out n I'm sure it's 134a refrigerant. I'm just worried about the stuttering compressor should I add another pound of 134a sense I only used one can could that help the stuttering or should I flush the whole system again? Or just buy a new compressor?

Mrman7627 · #10 07-12-2015, 03:31 PM

Or should I add a small amount of oil to the system cause stuttering compressor to me seems like a lubrication issue especially sense it DOES blow cool, air and it stutters more when I'm idle when I'm driving the issue isn't as bad I also noticed it doesn't squeak as bad if I press on the accelerator while idling and when I do this the air gets noticeably cooler then when idling

Mrman7627 · #11 07-12-2015, 08:03 PM

Okay update. I found out the reason the compressor was stuttering was because it didnt have enough freon but when it didnt it was still blowing cool air just not cold. So i bought more refrigerant started the car turned the ac on full blast then added more refrigerant. The compressor stopped stuttering and now engages when i turn the ac on and stops when i turn it off. But now it isnt blowing out cool air anymore its just blowing. The expansion valve is still cool to the touch not freezing but cool the bottom two hoses connecting to it feel warm and the top two feel cold But the compressor still spins and engages when its on so the system still has enough pressure to tell the compressor to engage. I hear the car start to idle differently when i turn on the ac as well. Also only one of the two fans on the radiator are spinning ive been led to believe that when the ac is on both fans should be spinning. Sorry if im being difficult this is the first time ive worked on my ac system before.

ROLLGUY · #12 07-12-2015, 08:17 PM

Quote:

Originally Posted by Mrman7627

Okay update. I found out the reason the compressor was stuttering was because it didnt have enough freon but when it didnt it was still blowing cool air just not cold. So i bought more refrigerant started the car turned the ac on full blast then added more refrigerant. The compressor stopped stuttering and now engages when i turn the ac on and stops when i turn it off. But now it isnt blowing out cool air anymore its just blowing. The expansion valve is still cool to the touch not freezing but cool the bottom two hoses connecting to it feel warm and the top two feel cold But the compressor still spins and engages when its on so the system still has enough pressure to tell the compressor to engage. I hear the car start to idle differently when i turn on the ac as well. Also only one of the two fans on the radiator are spinning ive been led to believe that when the ac is on both fans should be spinning. Sorry if im being difficult this is the first time ive worked on my ac system before.

Jump the 2 wires together on the fan switch on the drier and see if the fan/s come on. If the fan/s come on, your switch is bad. There are 2 types. One is a thermal type (not very reliable) that can be replaced without recovering the refrigerant, the other needs the system opened to replace. Check out the last link in my signature. In the installation guide on page 28 (and following) you will find a drier/switch tutorial. It should be helpful....Rich

Mrman7627 · #13 07-12-2015, 08:33 PM

I jumped it and the fan turned on ^^ yay. Unfortunately I have the one where the refrigerant has to be removed. Also felt the expansion valve while I had the fan jumped and it barely felt cold even after having the car on for a long time. I'm assuming that means that there is still a leak in the system it's just there is enough pressure in the system to tell the compressor to engage? Or sense I jumped the switch did something not turn on?

Whiskeydan · #14 07-12-2015, 08:50 PM

Recover what you have in there and change the dryer (again). Pull a vacuum for at least an hour with it sitting in the sun then charge it up with two cans of R152a.

Both of my 300SD make ice on the suction side line in the engine bay and the pressures are lower than R134. I can hardly hear, feel when the compressor kicks in.

ROLLGUY · #15 07-12-2015, 08:55 PM

Quote:

Originally Posted by Mrman7627

I jumped it and the fan turned on ^^ yay. Unfortunately I have the one where the refrigerant has to be removed. Also felt the expansion valve while I had the fan jumped and it barely felt cold even after having the car on for a long time. I'm assuming that means that there is still a leak in the system it's just there is enough pressure in the system to tell the compressor to engage? Or sense I jumped the switch did something not turn on?

You can make, or buy one of my relay kits that turns on the fan when the compressor is on. Then you have no need to discharge the system, as the fan switch on the drier is not needed....Rich