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2008 Dodge Ram HeaterTreater - Heat and AC Blend Door Replacement Parts


  This is a product developed by the HeaterTreater Engineers for the common HVAC modulation door problems on the Dodge RAM pickup trucks.  Please check our feedback to get an idea of the product line integrity and customer reaction to our products. We are committed to customer satisfaction and successful repairs of HVAC door problems. 

This listing describes the various doors susceptible to failure on the RAM.  From the descriptions you can determine which door(s) need repair on your truck.  The BUY section lists all the various combination of doors for the RAM.   We price the first door at $119.92 and any additional doors at $45.  This lower price for subsequent doors will be honored at a later date if you have additional doors go bad later. 

The HeaterTreater replaces any of the plastic doors in the system with steel. Replacing the existing door with another plastic door is at best a stop-gap solution. The failure is a result of excessive forces generated by the DC servo motor in the operation of the door. 

(If your RAM is dual control(separate control for passenger and driver’s sides) the HeaterTreater will connect the blend doors together and convert the system from dual control to single control from the driver’s side knob.  The back motor that controls the passenger side blend door is only accessible if the plenum box is removed. For a dual control RAM, this is a compromise between repair difficulty/cost and functionality.  For the single control, the system will operate exactly as it did when new.)

The HeaterTreater attacks the root cause of the failure by constructing hardware that is designed to meet the rigors of normal operation of the HVAC system, and last for the life of the automobile.  The kit includes detailed instructions and all hardware required to complete the fix, including dremel bits and metal tape to seal the cut

2002 was a changeover year for Dodge and there are 02’s with both the older and newer plenum boxes.   Check our other listing  for the older RAM product.   Pictures on both listings will help you determine which fix is right for your 02.  Note that relatively few of the 02’s used the older design.

Our primary business focus is replacing blend doors in late model automobiles.  The RAM is different from most automobiles in this age range in that the control of all doors is strictly electronic with no vacuum controls.  Most automobiles use a vacuum control mechanism for the “easy” doors with electronic controls only for the blend door.  Dodge chose to use DC servo controls for all the various doors and all of them are susceptible to failure.  This makes it a little more difficult to diagnose exactly what is wrong with the system.  We give a complete list of the various doors and failure symptoms below.  There are five(four separate, one follower) different doors in the system, all of which can fail.  We realize that most customers will want to replace only the bad door(s) and keep an eye on the others.  We are pricing the product with a set price for the first door and a much lower price for an additional RAM door or doors purchased in the future.  Our goal is to provide a complete solution over the life of your RAM without gouging every time something new goes wrong.

 

The standard Dodge fix for the door failure is to remove the plenum box and replace which ever door is failing.  Removal of the box requires removing the dash panel, removing steering wheel and steering column, evacuating and disconnecting the AC compressor, draining and disconnecting the heater hoses. Fixing the door is relatively easy, but the labor(and cost) of getting to the door makes this a time consuming and expensive job. The HeaterTreater avoids the hard work by providing a kit that allows the repair to be done with superior components without having to disassemble the automobile. 1-2hrs work vs 8-14 hours of work, and no specialized mechanical skills or tools required.

 

  
The Problem:

-  The RAM is built with multiple doors to control intake source, air flow through the heater core, and delivery to defrost/vent/floor.  The doors are controlled by DC  servo motors. The issue with the design is that the system has to calibrate itself and find the end points of movement before the computer can understand the two closed positions and regulate the position of each of the doors.  The motor is geared to move the doors slowly and with a good amount of force. The door has a limit pin which will break over time and the force is then transferred to the doors and axle.  Like bending a coat hanger back and forth, the doors will eventually break.   The calibration process is started automatically at a set interval by the computer and cannot be avoided.  It is the forces generated during calibration that lead to system failure. 

Do you have the problem?

The Dodge Ram Pickup truck has multiple doors that are DC motor controlled and all of them are susceptible to failure.  As mentioned above, the system is designed with a limit pin to control door movement.  The photo shows a good limit pin and broken limit pin.  If you observe a broken pin on any of the various doors, complete failure is not far behind.  Before ordering product, we suggest that you go through the different doors and fail modes to determine the problem(s) and make sure that we provide the right product. 

 

1.        Re-circ door.

a.       This door regulates between external air and internal air being pulled into the system.  It works by blocking the external intake vent, forcing air to be pulled from the internal intake vent, OR  blocking the internal intake vent, forcing air to be pulled from the outside.  There is no in between.  You can easily check the function by turning the fan on full blast and checking the air flow into the external vent between the hood and windshield.  With re-circ off, you should feel a strong air flow into the vent and it should stop when re-circ is on.  When the door fails, it hangs in the center and both the external vent and internal vents are open and air will flow into the external vent and out of the internal vent…like having a window rolled down all the time.  If you feel air coming in under the passenger side dash, this is most likely the problem.

b.      The photo shows the location of the re-circ door behind the glove box opening.  The door is covered by a grate and is in the upper right hand corner.  You can easily see/feel the door move when you have the system on and switch re-circ on and off.  If the door doesn’t  move or is missing, add this one to the list.

2.     Blend door.

a.       The blend door’s function is to divert some, or all, of the air flow through the heater core.  The RAM uses an odd, complex method with two blend doors.  The heater core is on a horizontal plane and two doors are sandwiched on the top and bottom of the core.  In full AC, both doors close against the core(top down, bottom up) and block any air flowing through the core.  In full heat, air is diverted through the core with the top door and the bottom door away from the core.   This blocks normal air flow in the bottom of the box, forcing more air through the top and down through the heater core.  The doors blend the air by partially opening and forcing some air through the core with some bypassing the core through the bottom door.  The two doors are linked together and operate in unison to control temperature.

b.      The symptoms of blend door failure are an inability to control the temperature of the air flowing through the system.  A broken door will generally fall into the down position, blocking the core and having no heat in the system.  The box is designed for either single or dual control of temperature on the passenger and driver’s sides.  If there is a difference between passenger and driver’s side temperatures, the problem is with the blend door on either a single or dual control system.  Of course this test assumes that the heater core is hot.  You want to make sure that the radiator is full(radiator, not overflow tank) which you can check by opening the radiator cap on a cold engine.  The radiator should be full, air in the system will greatly diminish heater operation and engine cooling.  You can also check the heater hoses from a cold startup.  The two hoses going into the firewall should warm up at about the same rate and get uncomfortably hot.  This is a good indication that coolant is flowing through the heater core.

c.    The RAM plenum box is built with dual air flow chambers so that the system can be configured for either single or dual control.  On the single control, the blend doors are just connected together and operate as a single unit, but there are still two separate air flow chambers.  The single control has a single actuator motor to control both sides of the HVAC system while the dual control has separate motors for either side.  Air flows through the AC evaporator core before getting to the dual chambers and if there is a temperature differential across the core, it can show up as a difference in temperature on the two sides.  Most auto makers constructed the core with refrigerant flowing from top to bottom on dual systems.  With this setup both sides would be the same and a lack of efficiency in the core would be equally spread across both sides.  Chrysler moves the refrigerant from right to left, so if there is a  temperature gradient across the core, the passenger side is at the back of the core and will see less efficient AC. Charging the system may solve the problem and at least it should be checked.  If the charge is too high or too low, it can cause a gradient across the core and it will show symptoms of warmer air on the passenger side.  This is a design flaw in the system and there is little margin for less than perfect operation of the AC compressor system.  You may have to “tune” the refrigerant charge, monitoring temperature on both sides, to get it perfect.   If the refrigerant charge is OK, the next suspect is the blend doors.  Dodge has a strange clam shell door arrangement for the doors in the RAM.  There are two doors, an upper and lower that move in unison and cover the top and bottom of the heater core which is on a horizontal plane.  On a single control system there are four different flaps(two sides/two sets of doors) that have to operate correctly.  The plastic components are susceptible to breakage and it is an expensive repair to remove and repair the plenum box when this inevitably happens.  The back door can break off exposing the top or bottom of the heater core to the air flow.  The system will still operate, but the added radiant heat from the core can significantly affect passenger side cooling.  The only way to really diagnose this problem is to cut into the box and observe the operation of the doors.  Once you have the box open, you can also check the temperature of both sides of the AC evaporator core to make sure that it is cooling both sides efficiently.  It takes a little work to get to the doors and check the operation, but once you understand the root cause of the problem, it can be restored to fully efficient operation. 

 

3.     Mode Door 1.

a.       This door regulates air flow to either the dash vents or defrost/floor.  If you have air flowing only through the vents with no defrost or floor, this door is failing.  From our experience, this door is usually the first domino to fail.  Not sure why, just is.

4.     Mode Door 2.

a.       When mode door 1 is set to divert air away from the vents and into the second stage of the system, door #2 chooses whether air goes to the defrost vents to the windshield or out through the floor vents in the passenger and driver’s side footwells.  Failure is indicated by an inability to choose between defrost and floor. 

b.      This door turns out to be the most difficult to replace.  In order to replace the door, the dash panel has to be removed.  It’s still better than the dealer fix because you don’t  have to evacuate the AC system, drain the radiator, and remove the plenum box.  But it is more work than the other fixes.  When this door breaks, it falls in the down position, blocking the floor vents and diverting all air through the defrost vents.  From a safety standpoint, this is good since you’d most likely rather have a clear windshield than warm feet.  We suspect that a large percentage of customers will just leave this door unrepaired.  You will have heat through the dash vents and to the windshield, just nothing to the floor.  It’s inconvenient, but you’ll have to make the determination if warm feet are  worth the extra work to fix the door.  An extra pair of socks is easier.

 

 

These are the symptoms of failure, you can also get definitive information by reading the HVAC DRBIII codes.  All of the actuator motors have a feedback to the computer system and a failure of any of the doors will show up in the fail codes.  The codes should line up with the symptoms, and when they do this is a complete diagnosis of the problem.  Note that the system will start throwing codes before the doors fail completely.  A code without symptoms means that the door is in the process of failing, but may have up to another year of life before it has to be replaced.  It will fail eventually, so keep an eye on it.

 

You can fairly easily remove the bottom cover of the dash and observe the operation of any of the doors and check for broken limit pins.  Check the TECH section for diagrams and the procedure for removing the bottom dash skirt.  A picture of the dash with the panel removed is listed below.  Note the metal stamped framework behind the dash cover.  The edges of the stamped metal are sharp, and we strongly suggest that you use duct tape to cover the exposed edges to keep your hands from look like you tried to pet the neighbor’s cat.

 

MOTOR FAILURE

Identical motors are used by Dodge to control the various doors.  It is a simple two wire DC motor that turns one direction when power and ground are applied and reverses direction when the power sources is switched.  It holds a steady position when both wires are positive or both negative.  All motor control is generated from the computer system.  The computer will overdrive the motor to a stall point at both extents of movement to determine the end points.  It is then capable of counting commutator clicks(motor revolutions) between these two points and can position the door anywhere between the stop points.  Note that the mode doors and re-circ door are either opened or closed, nothing in between (this is why most companies use a cheaper vacuum control on these doors).  When the computer detects a fault in movement of the motor, it shuts the motor down until the next calibration cycle to see if it “fixed itself”.  Of course, once the door has broken the motor will continue to send fail signals.  It is a mistake to assume that the motor is bad if it doesn’t appear to respond to signals from the control panel.  In actuality these motors are quite robust and failure is rare.  The problem is that the computer has shut the motor down, not a bad motor. 

 


The HeaterTreaterTM Solution:

This kit replaces the plastic doors and axle with steel components.  All work is done under the dash and through the glove box opening, and no removal of the dash or evacuation of the AC system is required.  Tools required are a screw driver, socket set, and a Dremel tool(if you don't already have one, this is a good excuse and the tool has many uses. The area under the dash is confined and you will need either a stubby Dremel tool(~6” long), or a flexible extension for a larger industrial rotary tool. Target has a new rotary cutter product from Durabuilt for ~$30 that includes a flexible extension, variable speed motor, and every grinding bit known to modern Chinese technology--except the one you really need which is included in the HeaterTreater kit).   
We prefer to use a dremel tool to make the cuts into the plenum box to replace the doors, but you can also use a hot knive or even an exacto knife if you don’t value your fingers.  We had one customer that used a steak knife and a cigarette lighter to heat it!!!  We recommend the Dremel, but it’s your RAM and you can do it any way you like.


The repair will take 1-2hrs, and once you have experience you can do the next door in about 45min.  No extensive mechanical skills are required.  The picture shows the metal replacement Blend Door kit.  The same construction techniques are used on the other doors and there are differences in axle length and door size, but they all look basically the same.  All functionality is duplicated in metal in the HeaterTreater kit and the system will maintain full functionality (only better with unbreakable components).  The plastic door is accessed by using the Dremel tool and bit to cut into the plastic heater housing from the front through the glove box and center console control panel(after removing it).  It's a relatively simple process.  The broken plastic door is removed and replaced with the
HeaterTreaterTM

The instructions are written with multiple pictures and dual level instructions.  You can read the bold print only for experienced mechanics or read the bold and standard for full "instructions for Dummies".  The instructions are almost insultingly simplistic for those who care to read the entire document without admitting that they did it.  The fix is not difficult and MUCH preferable to disassembly of the entire dash and engine cooling systems.   

We have designed fixes for multiple automobiles and this one is medium difficulty to install.  The factory fix requires complete disassembly of the dash and HVAC system, so this is a shortcut process that will save big bucks over taking the RAM back to the dealer.

We provide support via email (or phone if needed). Our goal is to make sure that every installation is successful. To date we have achieved that goal and have no intention of letting up. This will solve the problems with any or all of the doors and is over-engineered to outlast the RAM.  All our products are designed by degreed professional engineers and manufactured to exacting specifications.    This listing is fairly detailed and complex.  If your eyes haven’t glazed over yet, there is more on our web site with additional pictures.  We have successfully developed control door fixes for multiple automobiles and if for any reason the hardware ever fails it will be replaced at no cost.   Our solutions are tested for ease of installation and reliability and we WILL make sure that your repair is successful. 

 

 

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Patent Pending