Another AC thread - PeachParts Mercedes-Benz Forum

haromaster87 · #1 08-14-2013, 02:30 PM

Hey Guys,

So I'm ready to get serious about getting some AC in my 1984 300D. I have been reading all I can about the AC systems in these cars. I can't pretend to understand the system well yet, but I'm working on it. Right now, I'm getting familiar with the engine bay stuff, but I am at a loss with the control components. At this point, I think I'm going to need some advice catered to my situation, hopefully with you guys and some elbow grease, I can get some AC!

So my current system. I have the climate contol style with the dial and the horizontal buttons, like this:

http://www.msdra.com/old/300cdconsole.jpg

It has the air sensor on the dash as well. Right now, I have all of the vacuum disconnected from the climate control as I did it to eliminate shifting issues. I am aware that I will need to reconnect this and make sure the dash vacuum pods and lines are all tight, correct?

I'm also pretty sure my compressor is shot and that end of the system will need to be replaced. I will probably get the sanden compressor kit from the member on here to replace the compressor and I'll replace the lines, drier and check valve while I'm at it.

What it does now, it blows. It seems my blower motor is okay. When I press any of the climate control buttons, the blower motor kicks in and hot air blows out of the all of the vents. That's kind of where I'm at now.

I'm guessing I need to check out my monovalve too. I see that pop up in a lot of reading.

I know it's not much to work with, but like I said, this is where I can use some help. What additional components are there in the AC system that I need to check? Is there a way to test my control unit? I'm not necessarily looking to restore every function of the climate control. If I could just set it up to blow cold air when one button is pressed, and hot air with another, I'd be happy. So based on what I have so far, where should I go from here?

Thanks in advanced guys!

ROLLGUY · #2 08-14-2013, 08:50 PM

Quote:

Originally Posted by haromaster87

I know it's not much to work with, but like I said, this is where I can use some help. What additional components are there in the AC system that I need to check? Is there a way to test my control unit? I'm not necessarily looking to restore every function of the climate control. If I could just set it up to blow cold air when one button is pressed, and hot air with another, I'd be happy. So based on what I have so far, where should I go from here?

Thanks in advanced guys!

The only way I found out that I had a bad CCU, was to put in a different one and see if it worked differently. I found out the one in there was in fact bad, as there was no power to the compressor. I put in another one I had, and everything works great now. I am sure there is a more technical way to check it, but that was all I knew to do at the time, and I had several CCU's to choose from. I would say to check the easy things first. The monovalve diaphragm is easy to check, and the coil powers up for cool, NOT hot. If your A/C is calling for cool (thumbwheel all the way to the stop), there should be 12v at the coil (regardless if the compressor is working or not). You can also feel the hose going out of the monovalve when in A/C mode, it should not be hot. As long as you have a working fan and a good monovalve, you should be mostly there in terms of testing without the compressor working and fully charged.

wildest · #3 08-14-2013, 08:59 PM

Well, you didn't say anything about r134 conversion, but you may want to hit Rollguy's thread about the Sanden conversion kit he's making to use a newer compressor to get you cool. You may still need to address some of the vacuum pods, just to keep your tranny happy. And the more you do yourself, the more tools you'll need.

Edit: Rollguy got here before me..

ROLLGUY · #4 08-14-2013, 09:29 PM

Quote:

Originally Posted by wildest

Well, you didn't say anything about r134 conversion, but you may want to hit Rollguy's thread about the Sanden conversion kit he's making to use a newer compressor to get you cool. You may still need to address some of the vacuum pods, just to keep your tranny happy. And the more you do yourself, the more tools you'll need.

Edit: Rollguy got here before me..

The compressor will work with either R12 or 134a. However, the compressor is shipped with 6 oz of PAG oil, so it will need to be drained and filled with the proper oil if R12 is used. That is why most people that do a Sanden retrofit go with 134a. I use a 134a charge port in the high side hoses that I make, assuming (I know I should not assume) 134a is used. If someone buys a hose kit from me and wants to use R12, I need to know before making the hose. I am very happy with the results of 134a with the Sanden upgrade, and see no reason to go with R12. However, there are some folks that will not use anything but R12 in these cars. I have no problem with that...Rich

BillGrissom · #5 08-15-2013, 03:26 PM

Quote:

Originally Posted by ROLLGUY

The compressor will work with either R12 or 134a. However, the compressor is shipped with 6 oz of PAG oil, so it will need to be drained and filled with the proper oil if R12 is used.

The OP could also look at Duracool or Envirosafe (formerly Freeze-12). Both are hydrocarbons that work slightly better than R-12 and work with any oil (mineral or PAG), and use R-134A fittings. Next time, I might use Duracool's PAO oil, which sounds best (but pricey). There is a lot of information and even more mis-information out there, so read up, and determine for yourself if you need to worry about your car blowing up or catching fire (has never happened, probably extremely unlikely).

JamesDean · #6 08-15-2013, 04:14 PM

Quote:

Originally Posted by BillGrissom

The OP could also look at Duracool or Envirosafe (formerly Freeze-12). Both are hydrocarbons that work slightly better than R-12 and work with any oil (mineral or PAG), and use R-134A fittings. Next time, I might use Duracool's PAO oil, which sounds best (but pricey). There is a lot of information and even more mis-information out there, so read up, and determine for yourself if you need to worry about your car blowing up or catching fire (has never happened, probably extremely unlikely).

Envirosafe and Freeze12 are two different items.

Envirosafe is a hydrocarbon blend.

Freeze12 is a R134A blend.

I had F12 in the 190E for a while, it was not nearly as good as ES-12A.

vstech · #7 08-15-2013, 10:50 PM

Quote:

Originally Posted by JamesDean

Envirosafe and Freeze12 are two different items.

Envirosafe is a hydrocarbon blend.

Freeze12 is a R134A blend.

I had F12 in the 190E for a while, it was not nearly as good as ES-12A.

you are correct, but the company that used to sell F12 no longer does, and now they sell ES12, so the quoted post is sorta correct...

JamesDean · #8 08-15-2013, 11:10 PM

Quote:

Originally Posted by vstech

you are correct, but the company that used to sell F12 no longer does, and now they sell ES12, so the quoted post is sorta correct...

Interesting I didn't know that. I dont think I ever bought F12 myself. I think my shop put it in as an alternative as I was working on the cheap at the time and they wanted considerably more for the R12 that they had.

I've always bought ES-12 from either eBay or Environmentally Friendly Refrigerant and Automotive Fluid Products - Enviro-Safe, Inc