Now that it is hot again in the east, I have been using my AC in my SDL the last few days. The good news is that IT BLOWS COLD still! YEA!!!! One thing I find strange. When first starting the car and it is hot, the majority of the air at the center comes up through the defroster vents. Then after about 5 or 10 minutes, it shifts to the center vents above the console. Is this normal.

Also, my "recirculation" button does not light up and seems to have no affect. Everything else works fine, so I am not too concerned, but does anyone have any ideas as to a simple test of what it might be?

__________________
Alan Hamm
'87 300SDL 277K Miles
'89 560 SL 68K Miles

I'm not sure how the SDL A/C works, but I'm thinking that if the vents are vacuum operated, like in my 300D, a leak somewhere could possibly cause those symptoms. E.g.- turn the A/C on but it blows out the "default" defroster vents, until enough vacuum is applied to the center vent's actuator to open it.

Not sure about the recirculation.

According to the manual for my 87 the system automatically selects the lower vents when it senses warm air, and as the air cools it adjusts to the upper vents. Also, if the fan is set to auto, and the temp set to cool, the fan will not start till the evaporator cools. With a proper charge the AC should be blowing cold from the upper vents within the first minute. It could be delayed if you are not moving since airflow across the condenser is important for cooling. One way to check the charge is by looking at the sight glass after cleaning it with a rag and a small screwdriver. A few bubbles are ok but streaks or foam indicate air in the system.
You can also feel the line as it leaves the evaporator, it should be cool. I charge till the evap inlet and outlet are the same temp.

__________________
Brian
87 300Dturbo 180K #14 head still running R-12 SOLD 12/2017
02 F350 Powerstroke 180K
05 Chevy Express 1 ton w/Royal Utility box 120K
08 Infiniti FX-35 40K
15 Golf Sportwagen TDI 35K
10 Sprinter 3500 chassis with a Class A Winnebago on it. 56K