AC is working on Max AC only

[davidwatson833]

I have a 2010 ranger with 2.3L motor. My AC recently started working on the Max AC option only. For Max AC the console and windshield fan is working and the air is cool.
If I set to normal AC there is no console fan. The windshield fan is working and air is cool.

I took the cover off the fan in the engine compartment. That fan is working in Max AC and regular AC.
Also checked the screen and filter at that area. The screen is clear. I vacuumed the cabin foam filter, but it wasn't that dirty.

I opened the glove box to check the actuator and see if that opens. Not sure that applies in this situation. I don't see or hear the blend door actuator.
And the blend door with the foam cabin filter never opens. Not sure when it should.

Did notice the AC hoses have more condensation than what I expected. But since it so hot here, not sure if that applies.

The compressor, dryer and most of the AC was replaced last July. Not sure if the actuator was replaced.

 

[franklin2]

Here's a old post from Ron D.



The TEMP control **** runs the Blend Door, sends air from the fan thru heater core(HOT) or around it(COLD)

The Vent controls/doors are Vacuum operated, Defrost is the Default, no vacuum needed
Panel or floor require vacuum at the back of the climate control panel
Good news is that its a common issue with a common place to look for the problem

The engine is, of course, the source of the Vacuum for the cab vents
But it has a Vacuum reservoir that holds vacuum at a stable level, much like Power Brakes have the large vacuum reservoir, called the booster, that holds vacuum even after engine is off

So the Cab's Vacuum reservoir is a black plastic ball on passenger side at the front of the vehicle down low, its in front of passenger wheel in front of the wheel well
You need to know where it is to find its TWO black vacuum hoses
These are the hard plastic vacuum lines so "look like" wires
One hose comes from the engine of course, its possible but not likely this hose is bad, but you would have a high idle, which you don't mention

The other hose is the one you want to check, it runs along the top of passenger side frame to the firewall in engine bay
It often gets melted by hot exhaust manifold or pipe, or gets brittle from the heat and breaks, easy to repair with rubber vacuum hose of the right size, just splice it, no clamps needed its a vacuum line

Easiest way to find it is to look at the heater hoses and find the Heater Bypass Valve on the heater hoses, bypass valve will have a GREY vacuum hose
Follow that grey hose down to the firewall, it goes in next to/with the black hose and into the cab
Once you found that end of the black hose follow it in the engine bay to the reservoir "ball" and look for the break
95% of the time its this black hose that's damaged
4% would be a cracked Reservoir, especially if this vehicle was ever in a front end collision
1% would be disconnected engine vacuum hose, or vacuum issue inside the cab


HVAC Mode Door Actuator would be the actual Climate control **** on the panel, very unlikely for this to be the issue unless it has been physically damaged, i.e. hit with a hammer

 

[rubydist]

So it sounds like you either have an issue with the controls not sending the right signals to the various actuators, or you have a vacuum leak to the controls, or the actuator that determines whether the air goes to the defroster or vents or floor is bad. I would start by looking to see if there is vacuum to the heater controls or not.

 

[davidwatson833]

Thanks for the feedback. Couldn't determine the issue. Scheduled a time at the garage. I'll see what they find.

 

[davidwatson833]

So I took the truck to a garage. Went over everything, but wasn't sure what it is the cause. No leak in the hoses/vacuum etc.
Nothing else they checked indicated the issue. But it could be a bad ac control module.
Couldn't find a new one and they don't install used parts.

I found one on ebay and installed it. Same issue. So it isn't the control module.
Not sure how to say this. The knob that controls AC, Max AC, Off, etc. When it is set to regular AC what is on the other end of selection from the control module? Does it control a vent or other part.
If I wanted to replace the next likely thing it would be, any suggestions on where to start?

 

[franklin2]

I have never worked on a 2010. But as a general rule, A/C max opens a door to the interior, and the fan sucks inside air into the system to cool. In regular A/C mode, the door flips the other way and sucks outside air from around the wipers into the system to cool.

I re-read your original post, and there is no windshield fan or console fan. One fan, but the air is directed to these different places by the air doors. It should only blow air out of the defrost or windshield vents if "defrost" is selected, or you suddenly lose vacuum and it defaults to the defrost position.

This is a curious problem, but not life or death correct? You would run the A/C in max almost always on a hot day in Florida correct?

 

[davidwatson833]

I can just use Max AC, but generally don't. I'm concerned that whatever the issue will eventually select Max AC and I won't have any fan. Which door are you referring to. I want to view it in each mode so I can if it is working as expected.

 

[franklin2]

This is what we know already.


Air Distribution and Filtering
NOTE: The air distribution system of this vehicle cannot be equipped with a cabin air filter.

There are 2 sources of air available to the air distribution system:

• Outside air
• Recirculated air

Recirculated air is only used during MAX A/C (if equipped) and OFF modes.

Air distribution within the vehicle is determined by the function selector switch position. Airflow control doors are used to direct airflow within the plenum chamber. Vacuum control motors are used to position these airflow control doors. Refer to Climate Control System — General Information and Diagnostics for a description and operation of each of the system functions.

The air distribution system is designed to provide airflow from the defrost nozzle when no vacuum is applied to any of the vacuum control motors. This is done to prevent a situation where defrost cannot be obtained due to a system vacuum leak.

Air enters the passenger compartment from the:

• instrument panel A/C register.
• floor duct.
• windshield defroster nozzle.
• side window demisters.

Passenger compartment air is exhausted from the vehicle through open windows or cab air vents located on the rear panel of the cab.

 

[franklin2]

More information. Still do not know where the door is exactly. I would think you might be able to go from regular A/C to Max while looking under the hood and under the dash and you might see something. On the older large trucks this actuator was over near the pass side door hinge under the hood. I see it's called the "air inlet door".


System Airflow Description — Manual Climate Control

MAX A/C

When MAX A/C is selected:

• • The air inlet door vacuum control motor is at full vacuum, closing off outside air and admitting only recirculated air.
  • The panel/defrost door vacuum control motor is at full vacuum and the panel/floor door vacuum control motor is at no vacuum, directing airflow to the instrument panel A/C registers. A small amount of airflow from the side window demisters will be present.
  • The heater control valve is at full vacuum, preventing the flow of hot coolant to the heater core. Blended air temperature is not available.
  • The A/C compressor will operate if the outside temperature is above approximately 6°C (43°F).
  • The blower motor is ON.

A/C

When A/C is selected:

• • The air inlet door vacuum control motor is at no vacuum, admitting only outside air into the passenger compartment.
  • The panel/defrost door vacuum control motor is at full vacuum and the panel/floor door vacuum control motor is at no vacuum, directing airflow to the instrument panel A/C registers. A small amount of airflow from the side window demisters will be present.
  • The heater control valve is at no vacuum, allowing the flow of hot coolant to the heater core. Blended air temperature is available.
  • The A/C compressor will operate if the outside temperature is above approximately 6°C (43°F).
  • The blower motor is ON.

PANEL

When PANEL is selected:

• • The air inlet door vacuum control motor is at no vacuum, admitting only outside air into the passenger compartment.
  • The panel/defrost door vacuum control motor is at full vacuum and the panel/floor door vacuum control motor is at no vacuum, directing airflow to the instrument panel A/C registers. A small amount of airflow from the side window demisters will be present.
  • The heater control valve is at no vacuum, allowing the flow of hot coolant to the heater core. Blended air temperature is available.
  • The temperature can be adjusted to heat the air, but the air cannot be cooled below the outside temperature.
  • The blower motor is ON.
  • The A/C compressor will not operate.

OFF

When OFF is selected:

• • The air inlet door vacuum control motor is at full vacuum, closing off outside air from entering the passenger compartment.
  • The panel/floor door vacuum control motor is at full vacuum and the panel/defrost door vacuum control motor is at no vacuum, closing off airflow to the defrost duct, side window demisters, the floor duct and the instrument panel A/C registers. A small amount of airflow from the side window demisters will be present.
  • The heater control valve is at full vacuum, preventing the flow of hot coolant to the heater core.
  • The A/C compressor will not operate.
  • The blower motor is OFF.

PANEL/FLOOR

When PANEL/FLOOR is selected:

• • The air inlet door vacuum control motor is at no vacuum, admitting only outside air into the passenger compartment.
  • The panel/defrost door vacuum control motor is at full vacuum and the panel/floor door vacuum control motor is at partial vacuum, directing airflow to the floor duct and the instrument panel A/C registers. A small amount of airflow from the side window demisters will be present.
  • The heater control valve is at no vacuum, allowing the flow of hot coolant to the heater core. Blended air temperature is available.
  • The A/C compressor will operate if the outside temperature is above approximately 6°C (43°F).
  • The blower motor is ON.

FLOOR

When FLOOR is selected:

• • The air inlet door vacuum control motor is at no vacuum, admitting only outside air into the passenger compartment.
  • The panel/floor door vacuum control motor is at full vacuum and the panel/defrost door vacuum control motor is at no vacuum, directing airflow to the floor duct. A small amount of airflow from the side window demisters will be present.
  • The heater control valve is at no vacuum, allowing the flow of hot coolant to the heater core. Blended air temperature is available.
  • The temperature can be adjusted to heat the air, but the air cannot be cooled below the outside temperature.
  • The A/C compressor will not operate.
  • The blower motor is ON.

FLOOR/DEFROST

When FLOOR/DEFROST is selected:

• • The air inlet door vacuum control motor is at no vacuum, admitting only outside air into the passenger compartment.
  • The panel/floor door vacuum control motor is at partial vacuum and the panel/defrost door vacuum control motor is at no vacuum, directing airflow to the floor duct, the defroster duct and the side window demisters. A small amount of airflow from the side window demisters will be present.
  • The heater control valve is at no vacuum allowing the flow of hot coolant to the heater core. Blended air temperature is available.
  • The temperature can be adjusted to heat or cool the air below the outside temperature.
  • The A/C compressor will operate if the outside temperature is above approximately 6°C (43°F).
  • The blower motor is ON.

DEFROST

When DEFROST is selected:

• • The air inlet door vacuum control motor is at no vacuum, admitting only outside air into the passenger compartment.
  • The panel/floor door and panel/defrost door vacuum control motors are at no vacuum, directing airflow to the defroster duct and the side window demisters. A small amount of airflow from the side window demisters will be present.
  • The heater control valve is at no vacuum allowing the flow of hot coolant to the heater core. Blended air temperature is available.
  • The temperature can be adjusted to heat or cool the air below the outside temperature.
  • The A/C compressor will operate if the outside temperature is above approximately 6°C (43°F).
  • The blower motor is ON.

 

[franklin2]

Found it. It's behind the glove box door.

Vacuum Control Motor — Air Inlet Door
Removal and Installation

1. Release the stops and lower the glove compartment door.

• 

1. Remove the screws and disconnect the vacuum hose.

• 

1. NOTICE: Do not attempt to bend any part of the lever. It is brittle and will break.
   Rotate the vacuum control motor, disengage the lever and remove the vacuum control motor.

• 

1. To install, reverse the removal procedure.

 

[MaicoDoug]

its the blend door acautor located behind the glove compartment. The heater door is staying open & not closing @ the full cold setpoint. Acting like you set the temp to full hot in the AC mode. Its a good task to attempt for sure. Buy yourself a steak dinner when completed, you deserved it!!

 

[RedDragon777]

I am having a similar problem. When I turn on my AC in the morning it takes a while for the AC to switch from defrost to center vents. But only on MAX AC. If I change it to normal AC it will then switch back to defrost and no center vents. My truck is a 1998 2.5L Auto 2WD. I traced all of the vacuum lines in the engine bay and everything looks fine.

 

[franklin2]

Most of the door control vacuum lines are behind the dash. When it does finally switch do you hear a thump? I have had this happen to several cars and trucks. They use a foam on the doors to help them seal and make them quiet when they move. Much like the headliner foam, this foam on the doors gets old and sticky and can cause the doors to stick. When the actuator finally overcomes the stickiness it will move suddenly with a thump.

 

[RedDragon777]

Ok so I went under the dash and found the vacuum actuator for the floor and the dash vents. I watched them carefully and the dash vent actuator only pulls back on MAX. Then when I switch to AC it slowly creeps closed. So it is slowly losing vacuum. I also took a look at the floor vent and found that it does not work at all. No hissing or sound of lost vacuum. It just does not move. I tried to move it by hand and it is not seized so I figure it might be something behind the switch panel or the switch panel itself.

Or I could be completely wrong and the system just does not have enough vacuum and it is something under the hood. I am just confused because it holds vacuum on MAX, just nothing else.

 

[MaicoDoug]

Check the vacuum reservoir, pump it down and watch the blendor door open & watch the gauge for a "leak down" test. If that's ok see my prior post.