Another AC thread

[Whiskeydan]

Not the normal AC post however.

34-35f vent temp from a 'BLACK' W123 wagon.

[vstech]

um, rub it in why don't ya!
R 12 I am guessing?

[Oracle12345]

thats normal.....

[sixto]

The drop on the dash hits ant someone taking the thermometer out of an cooler full of ice, slipping it into the vent and snapping a picture as quickly as possible

Seriously, that's enviable. I have to clean my radiator and condenser because it feels like vent temp is 15* warmer at idle than at 40 mph.

Sixto
87 300D

[daw_two]

I'm going to ask the obvious. Tell us EVERYTHING you did.

1. New compressor? If not, then the age?
2. Flush?
3. Cleaned the Evaporator?
4. Cleaned the Condensor?
5. New dryer
6. New expansion (mono?) valve?
7. New O rings?
8. Which refrigerent?
9. What were your pressures at what RPM?
10. HOW fast are you driving when you measured the vent temperature?
11. WHERE were you driving when you measure the vent temperature?
12. What was the outside air temperature and humidity?

Well, you get my point.

Today, Coda center dash vent got to 59F at 45 MPH; outside air was 92, R12; have no idea what my low and high side pressures are --- no gauges. HINT, HINT, HINT.

[Whiskeydan]

Originally Posted by sixto

The drop on the dash hits ant someone taking the thermometer out of an cooler full of ice, slipping it into the vent and snapping a picture as quickly as possible

Seriously, that's enviable. I have to clean my radiator and condenser because it feels like vent temp is 15* warmer at idle than at 40 mph.

Sixto
87 300D

Hand was wet from condensate on the suction line going up to the compressor. No tricks here.

[vstech]

actually, those thermometers are KNOWN for being inaccurate! fill a glass with ice, then fill it with water, let the ice/water equalize and put the tip of the thermometer into the ice slurry. it should read exactly 32... if not, adjust the face to line up with 32.

[Whiskeydan]

Originally Posted by daw_two

I'm going to ask the obvious. Tell us EVERYTHING you did.

1. New compressor? If not, then the age?
2. Flush?
3. Cleaned the Evaporator?
4. Cleaned the Condensor?
5. New dryer
6. New expansion (mono?) valve?
7. New O rings?
8. Which refrigerent?
9. What were your pressures at what RPM?
10. HOW fast are you driving when you measured the vent temperature?
11. WHERE were you driving when you measure the vent temperature?
12. What was the outside air temperature and humidity?

Well, you get my point.

Today, Coda center dash vent got to 59F at 45 MPH; outside air was 92, R12; have no idea what my low and high side pressures are --- no gauges. HINT, HINT, HINT.

Stock 1980 300TD AC system was found to be low. I use a good vac pump and pulled it down to >30" (or would that be Confident there were no leaks I turned the pump back on and left it in the hot Texas sun running for six hours. Installed two cans of R12 and this is what I had. Still a bit undercharged but I'm happy and may add another can later.
I plan on adding a aux fan relay so it comes on with the compressor to aid in cool down time.

This pic was taken at around 5:30 pm today idling in the drive, no shade and the air in the cab was NOT cool. It must have been in the upper 90s ambient.

I still believe the evil servo must go. The vac pods are not steering the air as needed. With the evaporator this cold I want to take advantage of moving as much air as possible across it.

My plan in the future is to gut the servo and switch vacuum to each pod manually with spst switches. The AC compresor will be switched on and off with a simple op-amp circuit with a potentiometer on one input and a thermister on the other.
The blower motor speed will be regulated with a PWM circuit.
Hot coolant flow thru the heater core will be manually controlled with a vacuum valve and another spst sw.

I drew this design up a few yrs ago but sold the '79 W123 before I implemented it. Most of the parts are cheap/easily obtainable.
I'd think less than $40 for everything.

[Whiskeydan]

Originally Posted by vstech

actually, those thermometers are KNOWN for being inaccurate! fill a glass with ice, then fill it with water, let the ice/water equalize and put the tip of the thermometer into the ice slurry. it should read exactly 32... if not, adjust the face to line up with 32.

I'll do that right now. I just happen to have a glass full of iced liquid here in front of me. Water??? Will whiskey work?

[vstech]

heh... no, it's gotta be H2O, distilled would be best, but at least tap water. no alkeyhol...
no salt, no sugar... just water.
and the more ice the better, fill the cup above the rim with ice and let it melt a bit.
mix in WATER and let it sit. you are looking for equilibrium. it will be 32F/0C exactly. just ice can be colder, just water can be warmer.

[Whiskeydan]

Originally Posted by vstech

actually, those thermometers are KNOWN for being inaccurate! fill a glass with ice, then fill it with water, let the ice/water equalize and put the tip of the thermometer into the ice slurry. it should read exactly 32... if not, adjust the face to line up with 32.

You're right! It reads 30f.

Maybe I'd better boil some water and check for 212f. Oh... wait. What's my elevation???

[vstech]

ahh, only 2 cans in the system will give you very low temps... but not sustainable.
you need 2.9lbs... that's what? 3.86666666667 cans...

[vstech]

so you were off 2F... no big... get the correct amount of 12 in there and lets see what she can do!

[JimmyL]

He makes me crazy with his cold MB AC systems. {I just sent him a PM and cursed him!}
I was at his house last week and he gets out of his SD and goes around to get the baby out of the back. About 2 minutes later he grabbed my arm with his "still COLD" hand. Yea, rub it in Dan.......
He is the King of MB cold AC temps!
Was over there again yesterday and he was working on all kinds of other stuff and wasn't even focused on the wagon AC. We did ride up and down the road in it and the air was blowing out of the vents way above 90!
What a touch he has with these things......

[Whiskeydan]

Originally Posted by JimmyL

He makes me crazy with his cold MB AC systems. {I just sent him a PM and cursed him!}
I was at his house last week and he gets out of his SD and goes around to get the baby out of the back. About 2 minutes later he grabbed my arm with his "still COLD" hand. Yea, rub it in Dan.......
He is the King of MB cold AC temps!
Was over there again yesterday and he was working on all kinds of other stuff and wasn't even focused on the wagon AC. We did ride up and down the road in it and the air was blowing out of the vents way above 90!
What a touch he has with these things......

Its just another freak of MB AC systems. Like the W126 'meat locker' with R134 and its stock condensor.