Where is the vacuum blend door actuator location and replacement instructions?

Hi,

The blend air door isn't the problem. If you can change from heat to A/C, the blend door is good. If you can't change the airflow direction, the mode door actuator is the likely cause.

The airflow direction actuators (mode doors) are vacuum actuated. I was only able to find one pic from the manual which I attached below.

I circled the vacuum hose (number 1) in the pic.

Before you replace it, make sure there are no vacuum leaks which can cause the system to default to defrost. There should be a vacuum supply from the intake manifold of the vehicle which will route through the firewall into the controller.

If you can't locate it, disconnect the mode actuator vacuum, request air flow to change to the floor and see if there is vacuum to it. If there isn't, there is a leak before that point and the actuator is likely okay. If there is vacuum and it doesn't respond, the actuator is likely bad.

Let me know what you find or if you have other questions.

Take care,
Joe

If it will blow air and you can control the temperature but cannot get it to select the floor or dash that is the function/mode door actuator, not the blend door. Blend door controls temperature, function doors control air direction. Now in this case there are actually 4 different vacuum motors that control where the air goes. As the image says the default for them if the system loses vacuum is to switch to defrost and stay there. So I doubt the issue is the actuators but instead a vacuum leak that is causing the controls not to work. The main vacuum line for the controls comes off of the engine and over to the vacuum reservoir, then through a black line to a check valve and then through the firewall and to the back of the control head. It is a common thing for the lines to crack or the fittings to rot off and then the system stops working as it should. I would start at the intake manifold and check the vacuum lines from there to the vacuum canister. Then from it to the firewall. A quick test that might help you is to start the engine and shut off everything around you, then listen right next to the control head for a hiss indicating a vacuum leak. If you don't hear anything you can use a can of carb cleaner to spray a short burst towards the various vacuum lines and connectors under the hood wit the engine running. A sudden change in the engines rpm means you have a vacuum leak in that area. I suspect you will find the issue under the hood, if not then you will need to remove the heater control head to get to the back of it to test for vacuum there. For that you remove the center dash trim then the 4 screws that hold the control head in place. Once it is free locate the black vacuum line, it should have a good vacuum on it with the engine running at an idle.

Almost has to be a leak, if it was one of the vacuum motors you would only lose that function, so you might have the floor vents, dash and outside air, or dash defrost and vent. But to lose everything and have only defrost it has to be a loss of vacuum. Inside the vacuum motors is just a diaphragm and a couple springs. Apply vacuum to one side and it moves that way, apply it to the other and it moves that way, or in this case with the loss of vacuum the defrost opens because the springs in the units move them to that position as the failure mode, that lets you still drive the vehicle and still get some heat but tells you that something is wrong. I actually like the vacuum systems better than the electronics as they are generally a lot easier to diagnose. You pull the control head and use a vacuum pump to test the actuator and listen for the hiss of a leak. The only drawback is that it can become a mess of spaghetti if you have one of the fancy dual control systems.

A leak large enough to cause a code would likely be the same one causing the loss of the heater controls because the engine is getting air into a spot it normally doesn't. Something like a broken vacuum hose would easily do that. To find the leak is somewhat easy. Take a can of carburetor cleaner and spray it at the various vacuum lines under the hood with the engine running. The engine will rev up when it sucks the cleaner through the leak. Then just look in that area for the problem.
This will show you how it's done but not on your exact engine:
https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

It is under the dash attached to the heater core case. There will be three of them in the same area. One opens the dash vents, one the floor and one the defrost. The one you want is the farthest back toward the seats on top. Circled in the image.

Hi,

If you are referring to the actuator, it is basically behind the glove box and to the left. It will be mounted on the HVAC box. Is that what you are referring to?

Joe

The three you are looking for are on the left side of the case behind the dash, If you use a light and look up under the dash from the foot well you should see the actuators. You should be able to get to them without removing anything unless yours has the trim cover under the dash.

Hi,

For some reason, I don't have it listed under a Mazda. However, here are the directions for a Ford Escape, which I believe is basically the same vehicle. I hope it helps.

___________________________________

2002 Ford Truck Escape 2WD V6-182 3.0L VIN 1 SFI
Panel Vent Vacuum Control Motor
Vehicle Heating and Air Conditioning Air Door Actuator / Motor Service and Repair Procedures Panel Vent Vacuum Control Motor
PANEL VENT VACUUM CONTROL MOTOR
REMOVAL

pic 1

1. Remove the vacuum control motor.
1 Disconnect the vacuum line.
2 Remove the two screws.
3 Disconnect the vacuum control motor from the door lever.

INSTALLATION
1. To install, reverse the removal procedure.

___________________________________

I hope this helps.

Joe

Hi,

What part number did you find? The idea they sent the wrong part is a concern. I tried to look up a part number but nothing was available.

Let me know if you have the part number, send it to me. I'll try to help.

Take a look at the attached pic and let me know if that looks like the correct part. If it does, here is where I found it.

https://www.carparts.com/details/Mazda/Tribute/Motorcraft/HVAC_Defrost_Mode_Door_Actuator/2002/ES/6_Cyl_3-dot-0L/MIYH1525.html

Take care,
Joe

If you apply a vacuum to the hose port does your old part move or does air just flow through it? Just want to verify the problem before you get lost trying to hunt down the part.
The one they sent you looks like the one for the defrost and floor vents. In looking at the parts book I don't see the other one listed but Ford or Mazda should be able to get it, the Escape is virtually the same vehicle with the same HVAC system.