1993-1998 Jeep Grand Cherokee (ZJ) HeaterTreater - Heat and AC Blend Door Replacement Parts
Check
our other listing for the re-circ door fix also. Both fail modes
are common on the GC, and you need to check the operation of both
systems to fully understand problems.
This is a kit to do a
complete repair on the blend door malfunction that is common to 93-98
Jeep Grand Cherokees. It will work equally well on a RHD or LHD
GC.
Chrysler used a
variety of HVAC solutions on the ZJ, so you need to check the
application information below carefully to make sure you get the right
product. There were two main systems used for the GC.
The earlier system has the blend door actuator motor on the bottom of the HVAC plenum(heater box). The motor is located under the passenger side dash, above the transmission tunnel. Open the passenger door and kneel to look under the dash. You will most likely have to pull back the carpeting on the left side to see the motor. It will be attached to the bottom of the box. A picture from a box that was removed from a GC is shown for reference.
Some XJ's, particularly the dual control systems used the later design which was continued through 2004. This system has the actuator motor on the front of the box behind the glove box opening. You will need to empty and fully open the glove box to see the motor. On the right side of the box there may be a dampening assembly. Remove this by pulling the attachment up and out. (This is a miki-mauze assembly and was eliminated on later models. Our recommendation is to pull this out and throw it away. Consider this as an upgrade to the older system.) With the box half open, you will see two black rubber stops inserted into the dash frame. Pull these straight down to remove. Watch carefully how they come out since they have to go back the same way. You can re-insert the stops with the glove box fully open and the glove box will slide past the stops fit properly. The actuator motor is in the upper left hand corner behind the glove box. A picture of the motor is included for reference.
This kit is for the earlier (#1) above system. If you have the second type of system, check our 98-04 Grand Cherokee listing for the correct fix.
DIAGNOSIS
The ZJ blend door pivots on a vertical axis and can swing back and forth like a closet door when the axle connection breaks. It will swing to one of two positions...full heat or no heat. Sometimes
you can jostle the door by accelerating, hitting the brakes, turning
sharply, etc. and it will stay in one position as long as there is a
strong air flow holding it in place. However, you lose fine control over temperature and it's a hit and miss affair to get the temperature you want.
Those are the symptoms of the problem. You can do a complete diagnosis by removing the actuator motor and examining the axle interposer. You will have to pull back and hold the carpet to access the motor. It is held on with two Phillips screws and you will need an angle Phillips driver to access the screws. The motor pulls straight down to remove. You will now see a black interposer that fits between the motor connector and the bottom of the blend door axle. Sometimes you can pull this down and off with your fingers, but use a pair of pliers if it doesn't come easily. The
blend door on the ZJ is metal and it is usually this black plastic
piece that spans between the motor and the blend door axle that breaks
or cracks. Examine the interposer carefully for signs of cracking. You should be able to manually switch between heat and AC by turning the blend door axle with your fingers.
The actuator motor used on this system has an internal variable resistance position detection system. The motor is capable of turning 360 degrees with no internal stops built into the casing. When
the door connection breaks, the motor can turn past the point where the
electronics can detect the motor position and the motor will shut down
in a state of confusion. You may or may not be able to observe the motor turning when you change temperature. Generally the dealer will recommend replacing the motor when it fails to turn.
With the
HeaterTreater, we provide a stainless steel interposer to replace the
cheap plastic and full instructions and pictures on how to snap the
actuator motor open and re-index the gears to bring the motor back to
life. The repair is very simple and effective.
Note: Another common failure on this model is with the mode door. The symptoms are air flowing out of the defrost and floor vents only with no ability to change to dash vent air. The mode door is vacuum actuated and failure is usually related to the vacuum system. There is a vacuum junction connector under the passenger side dash on the left side. It is common for one of the kids to kick this junction, pulling the vacuum line off of the mode door actuator motor. The fix is very easy, just put the vacuum line back on and secure it with a zip tie. The
problem is that the vacuum actuator motor is located behind the heater
box and you have to remove the entire dash to get to the bad
connection, 6hrs to get to the actuator motor and 30sec to fix it. The HeaterTreater will not address this fail mode.
HeaterTreater is a reliable product
designed by degreed professional engineers with significant experience
in control theory and materials science. We don't claim
perfection, but have over-engineered this and multiple other solutions
to exceed functional requirements. The HeaterTreater is the
original and best product and we will bend over backwards to make sure
that the system works in your GC, and fully stand behind our products.
100% Made in
