W123 A/C Charge
 

Hey guys, haven't been on the forums in a while.

Since its 187 degrees outside and 325% humidity, I'm trying to get my 240D's A/C running. The system is bone dry due to a leak that caused the previous owner to re-charge the system about every 3 months. I'm currently trying to charge the system myself and I cannot seem to do it. I jump the compressor and start filling on the low pressure side, but the pressure just keeps increasing, and I'm not seeing anything in the little sight glass on the drier. It's charging up to about 50-60 psi and the engine bogs down considerably when the compressor is engaged.

Is something wrong? Do I keep filling on the low pressure?

I read that you might need to charge up the high pressure side, but only if it has 0 pressure, which is does not. It has pressure on the high side.

I'm afraid to simply keep filling the low pressure because the pressure just keeps rising. It doesn't seem like the system is accepting the freon. (R-134a)

Any help or suggestions are greatly appreciated.

1983 240D
270,652 miles and counting

I would suggest you to take it to the professional before you hurt yourself or do more damage to the a/c system.

Questions to ask yourself:

Do I know a/c well?
Did I check for leak?
Did I vacuum the system?
Any oil in the system?
Do I know which port is the low/high pressure?
Do I take safety precautions, safety glasses etc.

Never charge from the high side.

My guess is that you are never going to be happy with the performance of R134a.

I know how the thing works and I know what I should be doing and what should be happening.
I know it has a leak in the evaporator core. (freon lasts about 3 months)
This system was vacuumed a month ago.
Fresh oil.
Yes low pressure is front and center right between the radiator and the engine, high pressure is back down behind the alternator near the block.
Yes I always wear gloves, sometimes surgical and work, and if I'm not wearing my Oakleys I'm wearing safety glasses.

I understand the R-134a sucks in comparison to R-12 but this system has already been converted to R-134a and I can get it easily. I mean the vents either blow Satan's breath when the heat is on or ambient air when the knobs over on cool. I'm just trying to make the car bearable in the summer.

Good luck.

There are other options besides r12 and r134, especially if you have a leak.

You might want to start by reading Leathermang's A/C thread. You could have a stuck expansion valve. That might explain the pressures you are seeing. Of course I would suggest that you rebuild the entire system with a Sanden compressor, but I am a little biased (just a little :D).

If you had put that into your first post it would have been helpful for us knowing at what level you are working..

The AC thread in my signature might be very helpful... as Rollguy mentioned....

So you have used a Sniffer detector at the inside vents while it was running ( use low fan if you do this ) and it showed a leak in the evaporator ?

So you added oil without taking the system apart and flushing....and then measuring the oil you put back in..... perhaps you have too much oil in the system .....

Your questions about where to charge the system are troubling in terms of your safety... I hope you really study up before going farther or get a pro to guide you while you do it...

So often many DIYers just add refrigerant, not knowing much about A/C systems. I have been working on MB A/C systems for years, and have a LOT of experience with them. However, I still rely on the experts for the vac and charge. Although I have my own equipment to leak test, I still use experienced technicians with the proper equipment to do the leak test, vac and charge. Many DIYers have the time and money to do it over and over, but I only have the time and money to do it right the first time.....Rich

ROLLGUY ,
AMEN !

EDIT ''' AND a professional will likely refuse to charge a system if it has a known leak.... it may even be against EPA rules.. IE. Federal Law for a licensed operator to do that...
and the License one might get to buy refrigerant may mean a regular person will be subject to those rules..
IF someone is working from old stock they had before the rules were promulgated they may not be subject to them.. ' grandfathered ' in.. HOWEVER, I would not broadcast that situation if that applied to me....as some Federal Law Enforcement people have a lower sense of humor than you and I do.. LOL

134A is junk in these cars without extensive mods. Go buy some R152A aka air duster, multiply your factory charge by 0.56 for your charge weight.

W126s take 26oz of the stuff for example and call for ~46oz from the factory.

Must run ester or PAG oil. Will it work on mineral? Yes. 300E has mineral and ester mix now plus air duster for years.

Pressures mimic R12.

That is great, but there is probably not a shop on the planet that will work on it with that refrigerant inside. They don't want to contaminate their supply, or another customer's system.

I am well aware. :rolleyes:

The guy's car leaks out fully in three months and he is roasting to death driving to work. My 300E leaks out 50-60% charge in four months due to the typical W124 evap issue. 134A was terrible in it and cost more than R152A. There is no reason to use it.

He, like basically everyone here, does their own work. Chances of taking it to a shop for HVAC is likely zero.

Since we are pretty sure his car has an R4 Compressor... which has no oil sump...thus relies totally on the ability of a refrigerant to dissolve and CARRY the oil around the system to keep the compressor lubricated..
I always worry about using these other refrigerants ..... it might work one season... and cause a black death the next.. where stopping and fixing the situation might give him 6 to 8 years of good AC out of the current compressor...
Any of these old cars should also consider the addition of a high performance pusher fan up front... like the SPAL or something... as the air across the condenser is THE bottle neck of ALL air conditioner systems.... if you have GREAT air across the condenser it can compensate for less than ideal other factors ( Like R134a being less efficient than R12 )...
https://www.spalusa.com/

My latest w123 a/c rebuild job is getting a new, USA Sanden compressor running r12:). My experience here lately is that the r4 compressor from China are junk that leak at the case seal after a couple/few years.