Need a W126 (380SE) A/C system diagram or illustration

[bcolins]

I'm looking for a diagram or illustration of the complete 1985 W126 (380SE) air conditioning system. Can anyone point to one or paste one here? I tried "Search" and didnt find anything.

Brian

[pmckechnie]

bcolins, I have the A/C wiring diagrams for my 84 500SEL that is 7 pages long. I could scan them them then send them to you in You do have a US version and not a gray car don't you?

Paul

[bcolins]

Paul, not looking for electrical. Im looking for a diagram of the A/C freon loop, including compressor, evap, condenser, freon lines etc.

Brian

[pmckechnie]

Brian,
You can trace most of it except the expansion valve and evaporator core. The expansion valve is under the dash above the gas peddle and is hooked to the evaporator core inside the air distribution box. The thing in the low pressure hose (large one) under the hood that has fuel lines hooked to it is a fuel cooler. For the freon, it is just a straight tube. So we have from the compressor (small hose) to the condenser, from the condenser to the dryer, from dryer to the expansion valve (blue hose on most cars) to the expansion valve under the dash, then to the evaporator, out of the evaporator back to the expansion valve and then back to the compressor. Again, what is your problem? I have been working on cars all my life, the last 27 years in my own shop. I have seen most problems many times. I'm sorry I don't have a diagram of the freon flow on these cars but it is very much like many other cars. The fuel cooler is the only thing unique to the MBs and a very few other cars.
Paul

[bcolins]

Paul, I am putting this back together after a system flush. As both lines are the same size and the compressor is not marked H/L or S for suction etc. I wasnt sure which line was the suction side.

I concluded in a conversation with another party last night that is must be the line that follows along the driver's side wheel well back to the fire wall with the fuel cooler and I believe you are confirming that,...correct?

I have flushed the entire system, installed a new expansion valve and then on the recommendation of another, drained what oil I could out of the new compressor and installed it,........I did NOT know that I should measure the oil that came out seemed like maybe somewhere between 2-4 ounces came out,....but really no way to know for sure. I am now reluctant to move forward,....as I am told that I could have as much as 3-5 ounces of the compressor oil still in it or perhaps none,.....and now unsure of how much oil to install in the system. I just learned that there might actually be a drain plug on the GM R6 compressor,.....thinking I should perhaps try and drain it further,....or remove the compressor and drain it further by standing it up on end. Just need to get a baseline on how much oil is in the system,.............and then how much total should be in it after adding oil. I believe the total recommended for the system including all components and lines is 10 ounces of the pag 150 (I am converting to R134)

If this would be best discussed by phone to save on typing time, feel free to call me 512-913-3969. it is currently 10:30 AM central time (Sunday)

Brian

[pmckechnie]

Brian;
First, the hose with the fuel cooler is the low/suction line that comes from the expansion valve. You didn't mention a new dryer. Did you replace it also? My next suggestion is to find some R-12 somewhere as 134 just doesn't work well in these old 126's. Ben there, done that. I just started asking around and found out from a friend of a friend of a friend that so and so had some R12 he would give me. A/C works GREAT now.
For your problem now, you need to drain all the oil you can get out of the compressor. Some do have a drain plug, but not all do. Replace the dryer ifyou haven't, and put the 10oz of ester oil in the system. Pag is ok if you are sure all the mineral oil is out of the system. Pag and mineral oil do not get along. Ester will mix with either one. I would evacuate the system, then charge up with 80% of the amount of R12 called for. I believe 56 oz is called for so use 80% of 56 oz what ever that is. It is very hard to charge with 134 by just watching guages.
I don't do well on the phone as I have hearing problems so typing is better for me. Plus maybe someone else will add more information.
Paul

[bcolins]

Paul, Yes, I do have a new drier,...it will go on just before vacuuming the system down.

BTW, that 10 oz number came off a chart showing specs for the R6 compressor and a typical installation,....


(link to that chart here: http://www.rtitech.com/downloads/News/Oil%20Chart%20-%20Compressor.pdf )


..not a Mercedes 126 spec. Any idea if there is a 126 compressor oil spec anywhere?

Also, my new expansion valve is marked "R134A",....so thinking that it is designed to aid in making the 126 cars more efficient with R134A.

Brian

[bcolins]

Paul,...new information;

dug up the box the compressor came in and found an orange tag that stated,

"a small amount of assembly lubrican is in this compressor. It is compatible with all types of lubricants, do not remove"

So, I think that means I assume an empty system in terms of oil quantity to add.

[pmckechnie]

Brian You are correct. Add 10oz oil and charge up with 134 and it will work, just not as well as with r12. The 134 expansion valve should help (I didn't change the valve when I tried 134). The condenser is the main problem with the 126 and 134. Some people have converted to the parallel flow type but they had to make new mounting and new hoses and connectors. I don't know how much better they were. The volume of freon to use varies, depending on where you look but the only reliable source is the sticker on the radiator support if you still have one. I didn't. If you don't I would start with 80% of 54 oz or 43 oz. and see how it goes. You may have to add a little more, but do it slowly (2 to 3 oz at a time) and drive the car each time.
Good luck
Paul