A/C doesn't cool until car starts moving? Hmmmm
 

Need a data point of comparison (aka - how does this work in YOUR car?).

The car is my 84 300SD (W126).

When I start the car with A/C "on" and I let the climate control do it's thing - the A/C really doesn't do anything but blow air as the car idles in the garage. The air temp stays ambient (warm) as I sit and idle after start up. As soon as I get a little forward motion, down the alley even, air temp starts to drop like the A/C just got a wake up call.

So.... does the compressor need to build pressure in the system, or is engine RPM / speed needed to get the climate control going or is this just a symptom of needing a charge? Or is this normal?

Once I'm cruising down the road the car cools great, icy cold on the freeway. Temp guage never gets too hot etc. A/C at a light might not cool as effective (fan speed will have to kick up for example if I'm idling in traffic), but I figured that was because no air was going across the condensor. My main question is should the A/C kick-in quickly (within say 30 sec) of start up?

One, you need higher rpms to spin the compressor faster, and two maybie your condensor or aux fan isnt coming on. if you dont cool the condensor you wont get any cool air inside.

aux fans are working
 

You can hear those fans kick in! zooom!

I do wonder how RPMs play into this.... I would think idling would be enough (you need A/C sitting at a light in Texas - right?).

My 126 did that. It turned out to be that the auxiliary fan was not turning on when the A/C was turned on. With car running and parked, and hood opened, with A/C on, check to see if your auxiliary fan is on like it should be. Mine turned out to be the fuse for the fan which passes air through the A/C condenser, in front of the radiator. The only reason it seems to work better when the car is moving is because air is being forced through the condenser, and also forcing the fan to free wheel as the air passes through it....Luck to you.
Nick

My 124 does that a bit. It cools marginally when first starting the AC while stopped at idle. The aux fans cycle on and off by the temp sensor on the receiver/dryer. Start moving with RPM's over about 1500 and it starts cooling nicely after a while.

It was last recharged with dyed R12 just before I got the car in 2005, and I think it might have lost a little since then. The MB dealer that did it said it was low when they serviced the system, so there may be a very slow leak in there for it to still be working acceptably two and a half years later. We shall see how it fares next summer :rolleyes:...sure hope it's not the evaporator :eek: