For anyone whos HVAC fan slows down when accelerating
07-25-2003, 05:29 AM
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For anyone whos HVAC fan slows down when accelerating
I know we discussed this topic about 3 weeks ago but I thought some of you may want some more information. If your fan appears to slow down when you accelerate than you have a vacuum leak.
What is happening when you accelerate and the fan APPEARS to slow down is not the fan at all. The loss of vacuum makes the defrost/floor actuator to go to its neutral position which is feeding air to both defrost and floor. This door in the air duct has 3 positions. When no vacuum is present, it goes to neutral position. When vacuum is present it will go to one side or the other. The other 3 doors are either open when vac is supplied or closed when vac is removed.
With a vacuum leak, the other 3 doors close and the defrost/floor goes to neutral. The air is actually being diverted from say the mid level air vents to the defrost and the floor until the vacuum returns. Try feeling the defrost vent the next time this happens. Then the fan APPEARS to speed back up again as vacuum returns.
My problem was with the Bi-level actuator. I eventually found it and fixed it. None of the usual engine vacuum locations leaked. The check valve was fine, the line to the reserve tank was fine, the tank itself was fine.
The hose to the bi-level actuator had come loose. I didn't see how this could create a leak if I didn't select the bi-level location but apparently it was. So the bottom line is, IF YOUR FAN APPEARS TO SLOW DOWN WHEN YOU ACCELERATE THAN YOU DEFINATELY HAVE A LEAK SOMEWHERE AND IT IS NOT NORMAL FOR THIS TO OCCUR.
I can help anyone who has this problem if you need it.
What is happening when you accelerate and the fan APPEARS to slow down is not the fan at all. The loss of vacuum makes the defrost/floor actuator to go to its neutral position which is feeding air to both defrost and floor. This door in the air duct has 3 positions. When no vacuum is present, it goes to neutral position. When vacuum is present it will go to one side or the other. The other 3 doors are either open when vac is supplied or closed when vac is removed.
With a vacuum leak, the other 3 doors close and the defrost/floor goes to neutral. The air is actually being diverted from say the mid level air vents to the defrost and the floor until the vacuum returns. Try feeling the defrost vent the next time this happens. Then the fan APPEARS to speed back up again as vacuum returns.
My problem was with the Bi-level actuator. I eventually found it and fixed it. None of the usual engine vacuum locations leaked. The check valve was fine, the line to the reserve tank was fine, the tank itself was fine.
The hose to the bi-level actuator had come loose. I didn't see how this could create a leak if I didn't select the bi-level location but apparently it was. So the bottom line is, IF YOUR FAN APPEARS TO SLOW DOWN WHEN YOU ACCELERATE THAN YOU DEFINATELY HAVE A LEAK SOMEWHERE AND IT IS NOT NORMAL FOR THIS TO OCCUR.
I can help anyone who has this problem if you need it.
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