99 Buick Century AC Problems

[steelman]

I have a 99 Buick Century Custom. The A/C works fine, and the control module can change from heat to cool, and from bi-level, defrost, max, etc. When the A/C is on, especially in the early morning, it is blows a small amount of cold air through the vents as it shoulds, however, cold air is going thru the defrost vents to the windshield and creates condensation on the outside of the windshield. I either have to put the heat/defrost on to clear it or run the wipers. In just a few minutes, it will do the same thing again. It also looks like a small amount of cold air is coming thru the floor vents as well. It cycles and cools well, but when the A/C is on, whether on Normal or Max, a small amount is also going thru the defrost vent causing my windshield to hold condensation. I dont know whether this is a vacuum problem, actuator or blend problem, or what. I do not have digital air, normal 3 knob control head with the driver/passenger temp slide on the bottom. Before I take it to a dealer and pay a ton, thought I would join this Forum and see if anyone could help. I would appreciate it.

 

[dcraig1000]

are you running the a/c with or without the recirc selected?

 

[steelman]

It does not have a recirculation button on the AC control module. It does it whether the selection is Max or Normal. The car is equipped with Max, Norm, blend, defrost, etc. It has the base model AC Control module. (Cold-Hot). It has a slider on the bottom that controls the temp for driver or passenger. It appears to work fine. When the AC is on, it is cold on both sides when selected. It just allows a very small amount of AC cold air to go thru the defrost vent which causes the condensation on the windshield. I am assuming that Max is recirculated air, and Normal is pulling fresh air from outside the car. It creates the condensation whether on Max or Normal. I hope this information helps. I really appreciate your assistance on this problem.

 

[Aldaron]

I'd be looking at a vacuum leak, start from the intake penum to under the dash.If its the 3.1 its near the firewall on the pass side of the plenum where it hooks up.

 

[dcraig1000]

try to locate the blend door actuator and see if its moving all the way closed or stopping just short. there are adjustments and recalibration procedures, but make sure it needs it first

 

[steelman]

Is the blend door actuator under the steering column? I see a lot of posts that discuss this as a common problem. Looking at the drawing, it looks like the actuator may be way up in the dash. It allows just enough cold air to the windshield to create a problem. Also, there is a little cold air coming from the floor as well when in the AC Mode. I appreciate the help, just trying to figure out what might be the most likely problem without having to shoot in the dark and start parts changing. A friend of mine suggested that the defrost door seal my be bad and not completely sealing off. But he said that would be a major job and the entire dash would have to come out. He said that it would be very costly at a dealer. As it is allowing air to the defrost and the floor, it almost seems like airflow is escaping through one of the doors. What would be the more likely cause? Blend door actuator, AC Control module, vacuum leak, etc. I just need some direction on where to start. Can you see from under the dash if the blend door is opening and closing properly? Thanks for all the help. I really appreciate it.