94 C220 A/C Sensors?

My 94 C220 will not blow a/c air from the center vents initially when it is hot out. (about 80 degress and up) It will blow from the center vents on e/c mode so does that mean the flap isn't sticking? It seems as though it a sensor problem. Am I better off going the dealer, or should I try replacing one of the sensors first, which I am not sure of there location. Has anyone else had this problem? The car has a new a/c compressor, and once the car gets going (after about 5 very warm minutes) the a/c does blow from the center vents and works great. I usually run the system on e/c for a while then try a/c when it cools a bit inside. When it is really hot out, I have to repeat this process several times. Of course by this point I have melted!

I have also noticed when I get in the car on a hot day, the outside temperature reading on the dash has a really high number. Sometimes it says it's 110 degrees out, when it's more like 90 degrees. Could this be part of the problem?

Thanks!!!!

Michael

94 C220
89 300SE

[mbdoc]

The center vent is Vacuum controled & the signal comes from the pushbutton to a switchover valve assembly. I would guess that your car has a vacuum leak in the A/C system.

[jeffsr]

Are you saying that on Max A/C, the center vents only produce warm or hot air and then ultimately cools down?? If this is the case, then you may not have enough of a charge or the compressor is hitting against high pressure. If you are getting air flow on econ and air flow on max A/C, but the temp is not right, I'd take a look at that as well as what the DOC said.

I get no airflow from the center vents on the a/c mode initially only when it is hot outside. On e/c I get airflow from the center vents at all times.

The car shows no signs of vacum problems as far as air volume coming and going when accelerating.

Thanks!!!!!

Michael


94 C220
89 300SE

[jeffsr]

So the airflow slowly improves as you drive. If so, MB DOC is on target with vacuum leak diagnosis. If the actuator is slowly ever so slowly pulling in, the it's because it's suffering from inadequate vacuum. I,ll bet if you are doing 50 or 60 mph and you get off the gas and coast, the increased manifold vacuum will speed the process up.

I know you think it is vacum, but it sure seems more like it's electrical. When the air starts to come out of the center vents on a/c mode it is all of the sudden, and it doesn't matter if the car is moving or at idle the whole time. If it was vacum would it work on e/c and not on a/c? This problem has had me stumped for quite a while now.

Thanks for your advice!

I forgot to mention that before the a/c blows from the center vents, it is blowing from the top of the dash to the windshield and the side vents. When it starts blowing out the center vents, it stops blowing onto the windshield.

[jeffsr]

Well that is a horse of a different color..You are correct. If that sort of thing is going on, then the ACC is most likely at fault. It was not really clear from what you described before that was the way the criter was behaving. It sounds like the buttons are not releasing properly and your modes are getting scrambled.

I had the ACC replaced with a new MB unit. I know they had a lot of problems with them. I never use the defroster button, so it shouldn't be sticking.

Thanks!!!!