Climate Control Ramblings - PeachParts Mercedes-Benz Forum

Al Magaloff · #1 06-15-2006, 01:04 PM

Over the past weekend, I converted my 300SD back to R-12 from 134. Complete flush and evacuation, to be sure all traces of PAG were removed. New receiver/dryer, with the proper switches replaced with new. The compressor is also new, replaced when the 134 conversion was done, a few thousand miles ago. My '83 SD is the first MBZ I've owned. I've owned and driven many, many cars and trucks. I have never seen air conditioning performance like this car. On MAX AIR, within a few minutes from start up, the car actually becomes uncomfortable. The longer I drove, the more I found the need to "warm" the interior. Truly awesome performance.

leathermang · #2 06-15-2006, 02:06 PM

I am glad your AC performance is so good...
But I couldn't help but laugh when I saw " upper New York State"....
Even doing what you did correctly on some of our 20 plus year old cars you might have needed to clean the fins on the Evaporator to get that kind of results...... as DMorrison found.. almost 50 percent blockage can hamper overall performance.
Why don't you drive your awesome cooling machine to Centerville, Texas on July 29 and join in the festivities ?
All of your food that day is on my if you do...

Greg from Central Texas... it was 103 yesteday...

Brian Carlton · #3 06-15-2006, 05:42 PM

I, too, was appreciating the performance of the a/c on the SD today. Kept the interior quite confortable, provided the condenser was moving forward.

The ambient was 82 deg. F.

Al Magaloff · #4 06-15-2006, 07:39 PM

Greg, true, but relative. A car that's better than most @ 85º and 100% humidity, is better than most in Texas, too. Thanks for the invite though.

tangofox007 · #5 06-15-2006, 08:08 PM

Quote:

Originally Posted by Al Magaloff

The compressor is also new, replaced when the 134 conversion was done, a few thousand miles agao.

What type of seals does your compressor use?

JimmyL · #6 06-15-2006, 08:22 PM

Quote:

Originally Posted by tangofox007

What type of seals does your compressor use?

I second that question...

sonar23 · #7 06-15-2006, 09:38 PM

Quote:

Originally Posted by Al Magaloff

Greg, true, but relative. A car that's better than most @ 85º and 100% humidity, is better than most in Texas, too. Thanks for the invite though.

Where abouts in upstate NY are you located? I'm in Saratoga.

Thanks,
sonar23

Al Magaloff · #8 06-15-2006, 11:16 PM

Compressor was new for R12. I'm watching to see what it will do, after tasting 134. Rottenchester, Sonar.

TwitchKitty · #9 06-15-2006, 11:18 PM

Quote:

Originally Posted by Brian Carlton

I, too, was appreciating the performance of the a/c on the SD today. Kept the interior quite confortable, provided the condenser was moving forward.

The ambient was 82 deg. F.

Keep that condenser spotlessly clean for maximum efficiency. I ran searches and read about cleaning aluminum wheels here today and using those tips cleaned my condenser. It lowered pressures and temperatures by a significant amount. I am back on the gulf coast for a few more weeks and sitting in long lines of traffic at stoplights in 90deg temps is asking a lot of an AC. I asked and I got it.

JimmyL · #10 06-15-2006, 11:26 PM

Quote:

Originally Posted by TwitchKitty

I ran searches and read about cleaning aluminum wheels here today and using those tips cleaned my condenser.

What exactly were those tips? That would be good info for all....

pawoSD · #11 06-16-2006, 12:28 AM

Its going to be in the 90's here for the next few days, then high 80's for the forseeable future after that, I guess I'll have the windows down....

TwitchKitty · #12 06-16-2006, 01:03 AM

Quote:

Originally Posted by JimmyL

What exactly were those tips? That would be good info for all....

I was kinda hoping nobody would call me on that one.

I took the easy way out and bought a cleaner called Awesome. I didn't buy it because I thought it was the best option but because I have a dollar store I can get to without fighting traffic. The thread I read warned not to leave cleaners on aluminum very long or the cleaner may attack the aluminum. The bottle said to dilute the product so I just hosed the condenser with water first and rinsed out the dirt I could with the garden hose. I figured that water would also dilute the cleaner. I thoroughly sprayed the condenser with the cleaner and let it soak for several minutes. I then hosed out the condenser again.

Point number two that I didn't want to distract anyone with: I am working on my Subaru snow car with a 134a system that I drove down from Maine. AC fundamentals are the same, don't let any of this throw you.

Earlier I had determined that my pressures were too high and I could lower them by spraying the condenser with a water spray bottle. This simple cleaning lowered my high side pressure by 150 or so psi and my low side by 30 or so, too low. I charged the system up to about 28psi and now have cold AC idling in traffic at redlights.

This was a quick and dirty, get it done, kinda job and I am not especially proud of my workmanship but I am enjoying the results.

Al Magaloff · #13 06-16-2006, 05:10 AM

Twitch, a clean condensor is a better cooling condensor, for sure. I'm going to take a good look at mine. Most of those mag wheel cleaners are fairly mild, but effective.

TwitchKitty · #14 06-16-2006, 09:40 AM

Another interesting thing in the aluminum cleaning threads about cleaning aluminum trim, PB Blaster was said to do some chemical cleaning on aluminum. If you have a really crappy looking condenser it may be worth searching and reading about it. A two step cleaning of something like PB Blaster and an aluminum cleaner may do wonders.

Refrigeration shops sell chemical cleaners for condenser and evaporator coils, I would have gone this route if I wasn't working on my salted road beater and really short on time.

A clean evaporator would be just as important for efficiency and is aluminum also. I hate working under the dash though - maybe next year.

Condenser cleaning will be a yearly ritual for me. An invisible layer of road grime seems to be good for at least a few degrees of cooling from the vents.

I will be keeping an eye on this, my results almost seem too good to be true. A look at a buddy's SnapOn AC manual gave me a chart relating low side pressures to evaporator temps. That is where I came up with the 28psi low side for max cooling with 134a.

Pete Burton · #15 06-16-2006, 09:57 AM

Quote:

Originally Posted by TwitchKitty

Another interesting thing in the aluminum cleaning threads about cleaning aluminum trim, PB Blaster was said to do some chemical cleaning on aluminum. If you have a really crappy looking condenser it may be worth searching and reading about it. A two step cleaning of something like PB Blaster and an aluminum cleaner may do wonders.

Refrigeration shops sell chemical cleaners for condenser and evaporator coils, I would have gone this route if I wasn't working on my salted road beater and really short on time.

A clean evaporator would be just as important for efficiency and is aluminum also. I hate working under the dash though - maybe next year.

Condenser cleaning will be a yearly ritual for me. An invisible layer of road grime seems to be good for at least a few degrees of cooling from the vents.

I will be keeping an eye on this, my results almost seem too good to be true. A look at a buddy's SnapOn AC manual gave me a chart relating low side pressures to evaporator temps. That is where I came up with the 28psi low side for max cooling with 134a.

what does that manual suggest for R12?