Upgrade the A/C or improve performance? (85 300D) - PeachParts Mercedes-Benz Forum

frankengrant · #1 03-05-2011, 07:17 PM

What can be done to improve the performance of my A/C, it blows cold, but I know summertime here is brutal. Is there anything I can upgrade or do to make it better?

leathermang · #2 03-05-2011, 07:51 PM

I am going to suggest you go at this from the other direction than is usually suggested...

Read in the archives about cleaning the evaporator fins... those are inside the car under the dash... read DMorrison's account of how dirty his were... 99 percent of ours are the same way he found his... Usually we say things like clean the fins of the condensor, radiator, install newer type of condensor, etc...
But I am convinced that if you do this first.. and still think you need the other items.. that their impact will be much greater...no matter how perfect the rest of the system is.. if your evaporator fins are clogged up you can not be in too good a shape for keeping cool... and your system will have to work way harder to keep you at any level of cool... at the same time clean the water drain under those fins...

thatguy · #3 03-05-2011, 08:13 PM

Another thing you may want to consider is bypassing the sensor on the electric fan and wire it in such a way that it's always running with the compressor, or a manual toggle switch. I'm not sure how to go about doing that, but I added one on an older car (not Benz) with A/C that was on the weaker side and it really helped when sitting in traffic.

frankengrant · #4 03-05-2011, 08:16 PM

I looked at the DIY of removing the dash... far past what I can do at the moment, I need to practice that for sure before I attempt it.

What about this?

how to clean the evaporator fins on the air conditioner system?

Quote:

Originally Posted by snookwhaler

I did not take any pics when I did this. I was pretty hot out and I just wanted to get it over with. It was not nearly as accessible as the truck. I could only really feel part of it. It was every bit as dirty as the truck and I went in the same way (through the blower fan hole). Basically you just remove the lower passenger kick panel, unplug and remove the fan and go to work.

I just used a mild solution of soap and water with my pump up sprayer, along with an old toothbrush. I dragged the big stuff down to the bottom of the coil and then wiped it out. Then I just blasted the thing with a hose. It worked very good and some of that old musty car smell is gone. Took about 1 hour from start to finish. It blows much harder than before.

Yak · #5 03-05-2011, 08:40 PM

You can pull the blower motor and clean some stuff that way, you don't need to pull the dash. Several auto chain stores sell car-interior safe products for cleaning the evaporator.

But if it currently blows "cold", then what are you trying to improve? I'd put a thermometer in the exhaust and measure the performance. If the output temps are low, then the A/C system is okay. The compressor will actually cycle to keep from freezing up once the system reaches a low point.

If you want the interior colder and everything else is in order, then you may need to look into the "recirc" only modification.

There are a LOT of things to check and maintain if it's not cooling properly: vacuum pods, foam tube, blower motor, monovalve, thermostat, aux fan.

I think measuring the vent temps is probably the first step. That'll give a solid data point to gauge improvements.

frankengrant · #6 03-05-2011, 09:01 PM

I'm trying to improve the strength at which it blows, the other day on the highway something weird happend, I was going about 80 and my center vents started working, the A/C started blowing very hard as well. I can't get it to do it again, the center vents are closed again and I am not able to get them to reopen. The A/C now blows with the same medium strength it always has, cold, but weak.

snookwhaler · #7 03-05-2011, 09:19 PM

Follow post #2.

Cleaning the evaporator and condenser can help a lot. Especially if the system is working properly and is properly charged.

It is sounding like you have a vacuum problem too. Troubleshooting the A/C vacuum elements is not that difficult. But, it is a little time consuming to get to them so you can test them.

thatguy · #8 03-05-2011, 10:38 PM

Yep sounds like a vacuum issue to me as well, I bet cleaning the system as posted above and correcting the vent leaks will make it good to go. One thing to keep in mind, however, even if the a/c is charged fully with r-12 and everything is working perfectly, it simply won't have the cooling power of modern cars' a/c. These things are going on 30 years old and new technology really provides improved creature comforts.

charmalu · #9 03-06-2011, 05:01 AM

This DIY that Dmorrison did will give you an idea of what is behind the dash. he is working on a 83 240 and a 82 300TD at the same time.

Scroll down to picture 127 and you will see how dirty the evaporater can get after 25 + years. this will cut down on your AC cooling.

http://www.peachparts.com/Wikka/W123Evaporator

Charlie

frankengrant · #10 03-06-2011, 05:11 AM

Thanks for the link, thats the one I saw earlier that scared me lol.

So tomorrow I am going to take off the blower motor through the kick panel on the passenger side, stick my hand in there and wipe the evap core off with a brush or whatever. If I use a spray I need to make sure the drains work, how can I do this? Put some water in there and look under the car?

ngarover · #11 03-06-2011, 07:20 AM

holy hell... that looks like a job... As bad as changing expansion valve in a d1 rover... IF your going in this far I would be tempted to just go ahead and create a list like he does at the end and replace anything and everything you have access to at one time.

Yak · #12 03-06-2011, 11:34 AM

Setting max cold and hitting max fan may replicate what you experienced.

I've just uploaded some scans on how the airflow works. You could have a series of coincidences that caused your center flap to work/cycle: high speed = increased vacuum + stronger airflow = enough to overcome slight leak

Scans of airflow for W123 climate control

4thesporty · #13 03-06-2011, 12:52 PM

I believe once you make sure your drains are free, you can use a coil cleaner on the evap. It is sold in a spray can and foams on what you spray it on. After you let it work you rinse with water.

Just be careful with a brush as you don't want to bend any more of the fins while in there.

leathermang · #14 03-06-2011, 01:58 PM

Quote:

Originally Posted by 4thesporty

I believe once you make sure your drains are free, you can use a coil cleaner on the evap. It is sold in a spray can and foams on what you spray it on. After you let it work you rinse with water.

Just be careful with a brush as you don't want to bend any more of the fins while in there.

That is what I have been talking to him about...
Of course that stuff is cheaper if you get a gallon of it..
at a local professional AC parts store....

Be sure to get the one for INSIDE COILS....
there is one for outside AC home conditions which IS MORE CAUSTIC....
inside the evap you do not want to use the more corrosive one...

I have suggested not using a brush since if the fins are bent.... I do not think one will be able to access them with the standard ' fin comb' used by professionals to straighten them.. .due to tight access...

We don't want to make more ( and unfixable ) problems than we started out with... Well, unfixable unless you want to do what DMorrison did... and I sure do not want to do that ... or get anyone else into a position which would make that necessary to fix their car...

Yak · #15 03-06-2011, 02:18 PM

Quote:

Originally Posted by frankengrant

I'm trying to improve the strength at which it blows, the other day on the highway something weird happend, I was going about 80 and my center vents started working, the A/C started blowing very hard as well. I can't get it to do it again, the center vents are closed again and I am not able to get them to reopen. The A/C now blows with the same medium strength it always has, cold, but weak.

You didn't hit your defrost button by any chance, did you?