Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Tech Help

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 02-20-2018, 02:59 PM
ttownthomas
 
Join Date: Jan 2018
Location: Cary NC
Posts: 100
R12 System - Evacuate or not?

On my W126 300SEL The air is not cold.

The compressor kicks on but I am not getting much cooling if any, I know theses systems are somewhat complex but it seems to me like the appropriate vents are opening and closing based upon the different modes.

I have 2 cans of R12 but have read that "topping it off" is not advisable because you are not filling to the proper level and I don't have enough coolant to replace all of it. I also cannot seem to find a shop that will mess with R12 to even evacuate it properly.

I live in NC and want to daily drive this car but the summer here is no joke.

I spoke to a shop that suggested I just top off the R12 by adding it to the low side and watch the sight glass carefully to ensure the bubbles dissipate and call it good.

I am floating in the dark here as my expertise here is very limited.

Chris

Reply With Quote
  #2  
Old 02-20-2018, 03:16 PM
Registered User
 
Join Date: Sep 2011
Posts: 926
If you evacuate, are you going to capture what’s in there? Or vent it to the environment? I don’t think it’s easy to find a place that will capture it anymore. I could be wrong.

The reasons for evaporating are to assure you have the right mass and also assure the system is dry. My opinion is that if the system is still pressurized on the low side, then you are unlikely to have taken on significant moisture. I think evaporating this time of year is a horrible idea, since the hotter it is, the easier it is to evaporate any water in the system. Only evaporate if you have no pressure. That’s my VERY unprofessional opinion. Charge it by the low and high side pressures, and do everything you can to minimize r12 in our environment.


Sent from my iPhone using Tapatalk
__________________
Past mb: '73 450sl, '81 280slc stick, '71 250, '72 250c, '70 250c, '79 280sl, '73 450sl, parted: '75 240d stick, '69 280s, '73 450slc, '72 450sl,
Reply With Quote
  #3  
Old 02-20-2018, 04:40 PM
Hit Man X's Avatar
I LOVE BRUNETTES
 
Join Date: Sep 2004
Location: FUNKYTOWN
Posts: 9,087
Thumbs up

Are all of your vacuum pods actuating correctly? Check the recycle door. Verify the monovalve is closing too when on Max AC. Fan clutch actually work? Few do with age... a hint? Sachs ones are the only that work in my experience, spend the extra money for them. Also use the later fan for the M103.

Clean the condenser, the dual fan ones are a prick to do. Just do it. The evap needs a cleaning at this point too. 'Evap Powr-C' works boss for this procedure, just pick up a hand actuated container and wand to apply. It will take work, but worth the trouble.

If you have a leaky system, save the R12 for now. You probably have original orings and a leaking compressor. BTDT. Reseal the entire thing while it is cool out and flush it. Seriously. Use a syn compressor oil. Mastercool for the vac pump and Yellow Jacket or MC for the gauges.

A quick, cheap charge is with 152A if you just need to get by...did this in the 300E for years before it met its demise. Multiply your charge weight, 2.9lbs on the W126 by 0.54 and that is your 152A charge. Yes, it is air duster. It works as well as R12 pressure wise and cooling wise. You need two full, 10oz cans and one half of another. The last you have to meter in via pressure. I use R12 charts. Now if you can find 12oz cans, you are perfect. Two of them is pretty much full. Three, 10oz cans at my local Walmart are $12.

BTW, the car will never cool with faulty recycle and defrost pods. Tint will help cool the W126 vastly also. Even a mild 50% quality film.
__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.
[/IMG]
Reply With Quote
  #4  
Old 02-20-2018, 05:43 PM
Diseasel300's Avatar
Registered User
 
Join Date: May 2016
Posts: 6,025
Before getting all carried away, grab hold of the return line up by the brake booster and see if it's cold and/or sweaty. If it is, you know you have a problem with the air doors, OR you have an issue with the monovalve not shutting off all the way. If it leaks through, the amount of heat the heater core throws is enough to cancel out any cooling that takes place from the A/C system.

Are you also CERTAIN that the compressor is coming on? You see the center section of the pulley pull in and start spinning? If you're low on refrigerant, it's likely that the compressor will cycle a lot.
Reply With Quote
  #5  
Old 02-20-2018, 05:56 PM
ttownthomas
 
Join Date: Jan 2018
Location: Cary NC
Posts: 100
Quote:
Originally Posted by fonzi View Post
If you evacuate, are you going to capture what’s in there? Or vent it to the environment? I don’t think it’s easy to find a place that will capture it anymore. I could be wrong.
I would rather capture it but I have not researched how.
Reply With Quote
  #6  
Old 02-20-2018, 06:05 PM
ttownthomas
 
Join Date: Jan 2018
Location: Cary NC
Posts: 100
Quote:
Originally Posted by Hit Man X View Post
Are all of your vacuum pods actuating correctly? Check the recycle door. Verify the monovalve is closing too when on Max AC. Fan clutch actually work?

Clean the condenser, the dual fan ones are a prick to do.

If you have a leaky system, save the R12 for now. You probably have original orings and a leaking compressor. BTDT.

A quick, cheap charge is with 152A if you just need to get by

Tint will help cool the W126 vastly also. Even a mild 50% quality film.
So I assume there is a procedure to check the monovalve and the vaccum pods in the FSM?

Will do on the condenser.

Plan to tint to 35%
Reply With Quote
  #7  
Old 02-20-2018, 06:08 PM
ttownthomas
 
Join Date: Jan 2018
Location: Cary NC
Posts: 100
Quote:
Originally Posted by Diseasel300 View Post
Are you also CERTAIN that the compressor is coming on? You see the center section of the pulley pull in and start spinning? If you're low on refrigerant, it's likely that the compressor will cycle a lot.
The center section is definitely spinning. Don't know if its pulled in or not. Ill have to look again tonight.

Thanks for all the pointers everyone.
Reply With Quote
  #8  
Old 02-20-2018, 06:20 PM
Diseasel300's Avatar
Registered User
 
Join Date: May 2016
Posts: 6,025
Quote:
Originally Posted by ttownthomas View Post
The center section is definitely spinning. Don't know if its pulled in or not. Ill have to look again tonight.

Thanks for all the pointers everyone.
The pulley ALWAYS spin on the compressor. Just because it's spinning doesn't mean the compressor is engaged. Look at the center hub of the pulley. With the compressor off it will be stationary. If the compressor is engaging, you'll see it suck in and start spinning with the rest of the pulley.
Reply With Quote
  #9  
Old 02-20-2018, 07:27 PM
Hit Man X's Avatar
I LOVE BRUNETTES
 
Join Date: Sep 2004
Location: FUNKYTOWN
Posts: 9,087
Thumbs up

Quote:
Originally Posted by Diseasel300 View Post
Before getting all carried away, grab hold of the return line up by the brake booster and see if it's cold and/or sweaty. If it is, you know you have a problem with the air doors, OR you have an issue with the monovalve not shutting off all the way. If it leaks through, the amount of heat the heater core throws is enough to cancel out any cooling that takes place from the A/C system.

Are you also CERTAIN that the compressor is coming on? You see the center section of the pulley pull in and start spinning? If you're low on refrigerant, it's likely that the compressor will cycle a lot.


Great points.

I just assume the worst with 30 year old HVAC systems.
__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.
[/IMG]
Reply With Quote
  #10  
Old 02-20-2018, 09:11 PM
Diseasel300's Avatar
Registered User
 
Join Date: May 2016
Posts: 6,025
Quote:
Originally Posted by Hit Man X View Post
Great points.

I just assume the worst with 30 year old HVAC systems.
For sure! But if the system still has a charge of R12, I sure wouldn't be emptying it unless I had to!
Reply With Quote
  #11  
Old 02-20-2018, 10:27 PM
ttownthomas
 
Join Date: Jan 2018
Location: Cary NC
Posts: 100
https://youtu.be/f5VsbD5RVu8

The compressor is spinning. ^ I have not noticed it cycle off at all unless the a/c is turned off.

The high pressure line is not cool or sweaty
Reply With Quote
  #12  
Old 02-20-2018, 11:10 PM
Registered User
 
Join Date: Mar 2007
Posts: 159
The low pressure side is cool not the high side. The low side line is the larger. The high side should be hot.
Reply With Quote
  #13  
Old 02-21-2018, 12:18 AM
ttownthomas
 
Join Date: Jan 2018
Location: Cary NC
Posts: 100
Quote:
Originally Posted by TOPGUN View Post
The low pressure side is cool not the high side. The low side line is the larger. The high side should be hot.
My mistake. I was feeling the correct line I just assumed that the larger line carried the higher pressure. Here is the diagram from the FSM. I assume the expansion valve is in the dash somewhere?

Untitled by ttownthomas, on Flickr
Reply With Quote
  #14  
Old 02-21-2018, 12:21 AM
ttownthomas
 
Join Date: Jan 2018
Location: Cary NC
Posts: 100
here is what is happening at the sight glass

https://youtu.be/0rq8Zh4llh4

And I checked for the presence of 12v at the monovalve. It has 12v at max cool and 0 at any setting other than max cool.

That just means that the controller is sending the correct signal right? The controller is telling the monovalve to close but it may not be functioning correctly? Is there nay way to test the monovalve itself?

I will say that the heat did not seem to work correctly either during the cold spell we had 2 weeks ago.

Last edited by ttownthomas; 02-21-2018 at 12:31 AM. Reason: added info
Reply With Quote
  #15  
Old 02-21-2018, 12:24 AM
Hit Man X's Avatar
I LOVE BRUNETTES
 
Join Date: Sep 2004
Location: FUNKYTOWN
Posts: 9,087
Thumbs up

Low side with port is under the hood by the second firewall, driver side. Close to the brake master cylinder. High humidity it should sweat...like a cold Miller Lite on a hot summer day.

High line is post condenser, much smaller OD and runs in and out of the dryer. It should be pretty hot to the touch with a working system.

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.
[/IMG]
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -4. The time now is 03:57 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2024 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page