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  #1  
Old 01-09-2020, 09:57 AM
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W126 A/C questions/problems

My car got in a wreck awhile ago i had to replace the grille,radiator,condenser.It sat apart for awhile(6 months) and im just getting back to it putting together and wanting to charge the A/C. The lines for the A/C were open for the 6 months but i taped the ends not sure if that matters.

My first question is im not sure where my high pressure side valve is as i think the new condenser is a different layout and the only obvious place is not the right fitting maybe i just need to buy an adapter for it. I will attach pictures below

I have tried to do as much research as possible on how the process should go im more here to double check my process and get advice. I know i can take it to a shop and have this all done i enjoy trying to learn to do it myself if necessary i will take it in.

Im also not sure if this is all necessary after disconnecting the condenser or if i should just be able to add some oil/134A(pretty sure its been converted as the low pressure side has an adapter and blue cap) and be good to go. I have also read that i will most likely need a new dryer as the system was exposed to the air?

-Remove compressor drain oil
-Flush system. Do i need to take each line apart and flush everything separate or can i just flush the system as a whole?
-Install compressor with recommended amount of oil added(does oil need to be added anywhere else besides compressor)
-?Add new dryer in? before or after vacuum system
-Vacuum system
-Recharge system

Im sure there are questions i forgot to ask so i may bump/edit later with more but any advice you guys have is greatly appreciated

Edit:explanation of pictures
1:That is the fitting T'd off the main line going into the condenser from the compressor which im assuming is my high pressure valve. The other line going down and then 90's goes to the dryer
2:The compressor tag could not get a good picture can get numbers off it if needed i was wondering how much oil that model needed
3:Main line going into condenser from compressor(high pressure right?)
4:A cap on the compressor im not sure what it is but figured i would add a picture in case that was the high pressure valve
5:Low pressure hose returning to compressor

Attached Thumbnails
W126 A/C questions/problems-img_20200109_091501.jpg   W126 A/C questions/problems-img_20200109_092027.jpg   W126 A/C questions/problems-img_20200109_092135.jpg   W126 A/C questions/problems-img_20200109_092225.jpg   W126 A/C questions/problems-img_20200109_092254.jpg  

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Old 01-09-2020, 11:22 AM
Diseasel300's Avatar
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The high side valve is the one shown in your first picture. It is a standard 1/4" Schrader port for R12/R22. If you have a set of R134a gauges or if you're doing a proper conversion, you'll want to buy a quality adapter for it.

Since the system has been open, you want to flush the whole thing well. Drain the compressor, flush all the lines, remove the expansion valve (MAJOR pain on the W126) and flush the evaporator well.

While you have it apart, replace ALL of the O-rings on the various joints and smear them with Nylog before you reassemble. It'll save you from leaks for years to come. You're already in there, so why not.

Install a new filter/dryer. If going that far, replace the pressure switches on it, one controls the auxiliary fan, the other is a low/high pressure switch. Don't mess with the filter/dryer until you're ready to install it and switch on the vacuum pump.

The compressor is a Denso. It takes roughly 7 oz of oil. Consider using PAO oil instead of PAG. It has better lubricating qualities and is not hydroscopic (so it won't turn acidic from residual moisture in the system). It is compatible with R12, R134a, R152a, and Hydrocarbon refrigerants as well. The cap on the compressor is an auxiliary low side port. Leave the cap on. Replace the cap and Shrader valve if you feel like it.
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Old 01-09-2020, 01:23 PM
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Quote:
Originally Posted by Diseasel300 View Post
The high side valve is the one shown in your first picture. It is a standard 1/4" Schrader port for R12/R22. If you have a set of R134a gauges or if you're doing a proper conversion, you'll want to buy a quality adapter for it.

Since the system has been open, you want to flush the whole thing well. Drain the compressor, flush all the lines, remove the expansion valve (MAJOR pain on the W126) and flush the evaporator well.

While you have it apart, replace ALL of the O-rings on the various joints and smear them with Nylog before you reassemble. It'll save you from leaks for years to come. You're already in there, so why not.

Install a new filter/dryer. If going that far, replace the pressure switches on it, one controls the auxiliary fan, the other is a low/high pressure switch. Don't mess with the filter/dryer until you're ready to install it and switch on the vacuum pump.

The compressor is a Denso. It takes roughly 7 oz of oil. Consider using PAO oil instead of PAG. It has better lubricating qualities and is not hydroscopic (so it won't turn acidic from residual moisture in the system). It is compatible with R12, R134a, R152a, and Hydrocarbon refrigerants as well. The cap on the compressor is an auxiliary low side port. Leave the cap on. Replace the cap and Shrader valve if you feel like it.
Ok so hook the new dryer up after i flush but before i vacuum so i dont have to reopen the system after to put it in that makes sense.

You seem to be 100% correct about the expansion valve being a pain i went and looked at it and the ingoing high and outgoing low arent so bad but getting the top ports looks almost impossible. Maybe if i took the instrument cluster out could get them through that other then that it seems like take the dash apart. If i was to remove the expansion valve and flush the evaporator would it not spray out opposite tube either the ingoing or outgoing tube into the interior of the car? Would it not be sufficient enough to remove the ingoing high side on the expansion valve and flush the evaporator through that and let it leave through the expansion valve into the outgoing low pressure line down to the compressor where it will be disconnected?

Also for flushing is there an optimal PSI i should use i dont want to be to weak or to strong and damage anything.Is there a preferred cleaner i should use? I also read that you should flush the opposite way the normal flow is this true or does it matter?

Last edited by Whaling; 01-09-2020 at 01:39 PM.
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Old 01-09-2020, 01:34 PM
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The expansion valve can be accessed more easily if you remove the bolts holding the crash bar in place and dismount the crash bar. There are 2 bolts on the transmission hump and 1 or 2 up behind the cluster. If you choose to go without dismounting the crash bar, you'll be inventing new swear words, I can promise that (I've done it and don't recommend it). Crows foot wrenches are your friend, the skinnier the jaws, the better. Now is the time to replace the expansion valve as well, the original one has an orifice and power head setup for R12. The modern replacements have the orifice and power head setup for R134a which has a smaller molecule size and higher operating pressure. It makes a big difference in the final result, so worth the $30 or so for a new one.

Flushing the evaporator is best done with the expansion valve removed. Connect a hose to the discharge side and route it out of the car into a bucket. You can purchase Flushing kits on various websites such as Amazon. For a through flush, count on at least 2 quarts of flushing solvent, followed by plenty of air to blow out the residual solvent. I typically run 40PSI for flushing and 80PSI for blowing the lines out afterwards. Standing pressure of refrigerant in the system is >100PSI, so you're not going to be damaging anything from your shop air source.
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Old 01-09-2020, 02:33 PM
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Quote:
Originally Posted by Diseasel300 View Post
The expansion valve can be accessed more easily if you remove the bolts holding the crash bar in place and dismount the crash bar. There are 2 bolts on the transmission hump and 1 or 2 up behind the cluster. If you choose to go without dismounting the crash bar, you'll be inventing new swear words, I can promise that (I've done it and don't recommend it). Crows foot wrenches are your friend, the skinnier the jaws, the better. Now is the time to replace the expansion valve as well, the original one has an orifice and power head setup for R12. The modern replacements have the orifice and power head setup for R134a which has a smaller molecule size and higher operating pressure. It makes a big difference in the final result, so worth the $30 or so for a new one.

Flushing the evaporator is best done with the expansion valve removed. Connect a hose to the discharge side and route it out of the car into a bucket. You can purchase Flushing kits on various websites such as Amazon. For a through flush, count on at least 2 quarts of flushing solvent, followed by plenty of air to blow out the residual solvent. I typically run 40PSI for flushing and 80PSI for blowing the lines out afterwards. Standing pressure of refrigerant in the system is >100PSI, so you're not going to be damaging anything from your shop air source.
Ok thank you for all the advice i really appreciate it i will probably put this project off for a week or 2 and tackle it then when im not so busy. I found what seems to be a good write up for removing the expansion valve. I will post the link after if it all works out good and give some follow up advice for anyone else looking to do this. You saying how the expansion valve are made for different refrigerants i wouldn't want to get an older style original one that is not compatible with r134a do you think these two products are fine.

Expansion valve:
https://www.pelicanparts.com/More_Info/1268300384AINT.htm?pn=126-830-03-84-A-INT&bt=Y&fs=0&SVSVSI=

Dryer:
https://www.pelicanparts.com/More_Info/UR1268300383.htm?pn=UR-126-830-0383&bt=Y&fs=0&SVSVSI=3481

Did you mean to run 2 quarts of solvent through that evaporator or 2 quarts for the flush of the whole system. Also should i flush the compressor while i have it on the bench and before i add new oil into it?
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  #6  
Old 01-09-2020, 05:49 PM
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If you're replacing the expansion valve, shell out the extra $5 for the Egelhof (ACM) branded one. https://www.pelicanparts.com/More_Info/1268300384.htm?pn=126-830-03-84-M23&SVSVSI=3404&DID=2415

I ran the Uro one in my SDL when I first resurrected that system and it had a bad habit of hunting and making lots of noise under the dash. Not sure if it had debris in it or just a bad example. I replaced it with the ACM one with no issues. When I redid the 350SD, I used the ACM in it, also without issue. I'm running the Uro filter/drier in my 350SD without issue, no leaks.

2 quarts of solvent should do the whole system. Since you don't have to flush the condenser since it's brand new, you don't have to factor in solvent for it. No need to flush the compressor. Drain it out, spin the center section several times to pump out anything in the cylinders, and fill it with fresh oil through the suction side. Spin the center section a couple of times to distribute the fresh oil through the rotating parts just to prevent the possibility of a dry start.
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Old 01-09-2020, 06:29 PM
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Thanks for the feedback Diseasel300, we haven't received any reports of this Expansion Valve hunting or making noise, but we'll make a note of it just in case we hear anything similar in the future.
https://www.pelicanparts.com/More_Info/1268300384AINT.htm?pn=126-830-03-84-A-INT&bt=Y&fs=0&SVSVSI=3450

This valve has received 5-star ratings on that big retail site, but only has two reviews so not a lot of history yet.

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