123 with a Sanden and R134a: vent temps - PeachParts Mercedes-Benz Forum

ROLLGUY · #1 04-29-2013, 03:27 PM

I measured the vent temperature on my 240 today. I am running a 5 cylinder Sanden compressor, stock condenser and evaporator, R134a refrigerant, and the condenser fan running all the time that the compressor is running. It actually read 30 degrees for a second, but right as I took the photo, it went up to 31 (hard to hold the thermometer with one hand an take a photo with the other). When I took the photo, it was about 90 degrees outside here in So. Cal.

I am having to adjust the temperature wheel a little on the warmer side, as it starts to get real cold. The compressor cycles on and off, but still keeps the cab cool. I am installing a 7 cylinder Sanden on my 300D in a few weeks, and it may do a little better.

bd1308 · #2 04-29-2013, 03:57 PM

*that* is incredible.

andrewjtx · #3 04-29-2013, 05:03 PM

Brrrrr

Codifex Maximus · #4 05-27-2013, 12:25 AM

What kind of a load hp wise does it put on the engine and possible effects on mpg?

I like my mpg but... I think I could get used to 31 degree vent temps rather quickly.

ROLLGUY · #5 05-27-2013, 01:21 AM

Quote:

Originally Posted by Codifex Maximus

What kind of a load hp wise does it put on the engine and possible effects on mpg?

I like my mpg but... I think I could get used to 31 degree vent temps rather quickly.

I am finding a slight power loss noticeable on the 240, but I am sure a turbo 617 will not even know the compressor is there hard at work. My 240 is a 1982, and it seems to have a considerable amount more power than my friends 1980 240D. I have been getting about the same highway MPG as my vent temp with the veg oil blend I am running.

Doktor Bert · #6 07-15-2013, 07:26 PM

Quote:

Originally Posted by Codifex Maximus

What kind of a load hp wise does it put on the engine and possible effects on mpg?

I like my mpg but... I think I could get used to 31 degree vent temps rather quickly.

That is very good for a thermal expansion valve system on R134!!!!!!

I run high 20's low 30's on R12, but that easier than R134!!!!!

Nice work!!!!!

vstech · #7 05-27-2013, 12:59 AM

31° F vent temps equate to a coil temp below 23F... that means ice is forming on your evaporator coil, and will cause ice ups and reduction in capacity, and damage to your compressor by slugging liquid refrigerant through destroying your valves, and washing the crank of oil... a bad thing.
it's why there is a 35° switch in there to prevent it...

ROLLGUY · #8 05-27-2013, 01:15 AM

Quote:

Originally Posted by vstech

31° F vent temps equate to a coil temp below 23F... that means ice is forming on your evaporator coil, and will cause ice ups and reduction in capacity, and damage to your compressor by slugging liquid refrigerant through destroying your valves, and washing the crank of oil... a bad thing.
it's why there is a 35° switch in there to prevent it...

Yes, and thankfully that switch is working properly. After cooling down the cabin, on low fan speed the compressor cycles on and off (I can feel the slightest drop in power when the clutch engages). I usually roll the temp wheel all the way to the white to keep from freezing my arms. Of course on extremely hot days, it takes longer to cool the cabin, and the compressor stays running most of the time.

Doktor Bert · #9 07-15-2013, 07:30 PM

Quote:

Originally Posted by vstech

31° F vent temps equate to a coil temp below 23F... that means ice is forming on your evaporator coil, and will cause ice ups and reduction in capacity, and damage to your compressor by slugging liquid refrigerant through destroying your valves, and washing the crank of oil... a bad thing.
it's why there is a 35° switch in there to prevent it...

I've been running this thing like this for 88,000 miles. I have found that the fin surface temps never get as cold as the air temps, when checked with an infra-red...FWIW

ROLLGUY · #10 07-25-2013, 07:42 PM

I finally got my 7 cyl Sanden working in my 300D. The vent temp is 40 degrees:

The ambient temp is around 100 degrees (in the shade):

I borrowed the IR temp gun at my local radiator shop when I took the photo of 31 degree vent temp (first post), and just realized that it must be taking into account wind chill. I tried it on my 7 cyl Sanden in the 300D, and it read 17 degrees. I will take a photo in the 240 vent with the same thermometer I used in the 300D, and compare.

Fattyman · #11 07-26-2013, 12:09 AM

Good thing my wife doesn't frequent internet forums. If she saw what the AC is capable of my free time would be spoken for

.
Just think how bad it would be if she hopped in my car and turned on the AC!

Of course I could say I'm just experimenting on my car first......

ROLLGUY · #12 07-26-2013, 12:15 AM

Quote:

Originally Posted by Fattyman

Good thing my wife doesn't frequent internet forums. If she saw what the AC is capable of my free time would be spoken for

.
Just think how bad it would be if she hopped in my car and turned on the AC!

Of course I could say I'm just experimenting on my car first......

Please give me her contact information

leathermang · #13 05-08-2015, 09:09 PM

Quote:

Originally Posted by Doktor Bert

I've been running this thing like this for 88,000 miles. I have found that the fin surface temps never get as cold as the air temps, when checked with an infra-red...FWIW

FWIW..... an infrared thermometer has certain rules due to the physics of the situation... it would take a contact thermometer on the fins to determine accurately their temperature..... as you have experienced.
There is no way for the air at the vents to get colder than the fins on the evaporator....
Listen to Vstech ..... an AC professional.....

When someone has done all the normal update stuff to one of these old cars and is not getting the cooling they expect....
it is almost certain that the FINS on the evaporator are clogged..dog and human hair, pollen, etc over the years builds up.... and the fins on the condensor also need to be straight and clean... with a high performance fan running all the time the AC is on.... even more important if using R134a. Just due to its slightly less efficient molecular structure...

Robot B9 · #14 07-26-2013, 10:36 AM

Hi, just for some data:

82 240d, new R4 compressor, Klima cross flow condensor, with about 28 oz of R134a.

Under good conditions I get around 40f at the vents with fan on med.

MBeige · #15 05-11-2014, 02:30 AM

Cool! Nice mod Rich.

Do you have the stock aux fan? Or did you get the larger unit from a V8 W126?