2005 Merc Mountaineer manual third row seat won't release to raise from down position. What can I do to raise the seat?

If the motor is turning but the seat is not raising you have gear of shaft, issue.
https://www.explorerforum.com/forums/index.php?threads/3rd-row-electric-seat-back-wont-elevate.266947/
https://www.cargurus.com/Cars/Discussion-t7785_ds754401

copied this from ford forum , quite a lot of work, do your seats fold down into the floo ? if so follow this guidance
Removal and Installation

CAUTION: To prevent possible damage to the third row seat or the safety belts, make sure that the safety belts are not fastened when moving the seat to the load floor position.

CAUTION: Make sure that no objects such as books, purses or briefcases on the floor in front of the third row seats or on the seat cushion before lowering the backrest(s).

NOTE: The third row seat backrests need to be in the raised position for removal of the third row seats.

All seats


Remove the load floor panel.
Remove the jack assembly.
Remove the load floor panel latch striker bolts and the latch striker.
Remove the 3 pin-type retainers and the jack storage compartment liner.
Remove the 2 bolts in mid-floor panel support, lift on the front of mid-floor panel support to release the 3 retainer clips and remove the panel support.

Your missing something's G-404 has nothing to do with it !
Seats - Third Row
The third row seat:

• is three-passenger seat.
• a 60/40 bench seat.
• folds down for more cargo area.
• has optional power fold down seats.

Third Row Power-Fold Seat
CAUTION: To prevent possible damage to the third row seat or the safety belts, make sure that the safety belts are not fastened when moving the seat to the load floor position.
CAUTION: Make sure that no objects such as books, purses or briefcases are on the floor in front of the third row seats or on the seat cushion before lowering the backrest(s).
The third row power-fold seat consists of the following electrical components:

• right third row seat relay.
• left third row seat relay.
• right power-fold seat motor.
• left power-fold seat motor.
• right front third row seat switch (if equipped).
• left front third row seat switch (if equipped).
• right rear third row seat switch.
• left rear third row seat switch.

For the third row power-fold seat to operate, a shared ground is supplied by the body security module (BSM) to both of the power-fold seat relays, enabling the seats to then be moved by pressing one of the third row power-fold seat switches. The third row power-fold seat operates only when the vehicle is in PARK and the liftgate glass, liftgate door or any entry door must be open.
The third row power-fold seat motors transfer movement to a drive gear assembly to raise and lower the seat backrest. The power-fold seat motors rotate a short drive cable which is connected to the drive gear assembly.
The relay's are located in Aux. relay box #2

There is a cable that connects the handle to the latch, the cables like to break/stretch, sometimes if you look close at the rear of the seat where it attaches to the floor you can see the latch and manually release it with a long screw driver or similar tool.
Cables are avaiable from GM dealer if thats the problem.

mechanism lower seat driven by electric motor is broken.

Power 3RD Row Seat Problems and Tranny Shutter - Ford Truck ...

www.ford-trucks.com > ... > Expedition & Navigator

Mar 27, 2014 - Expedition & Navigator 1997 - 2002 and 2003 - 2006 Ford Expedition andLincoln Navigator SPONSORED BY: ... First the 3RD row seats won't fold down, noclicking, no sounds, nothing. I the fuses are good and there is power at the fuse box, but no power at the motors or switches. Based on continuity ...

3rd row powerfold seat stuck down - Ford Truck Enthusiasts Forums

www.ford-trucks.com > ... > 2007 - 2014 Expedition & Navigator

Mar 14, 2010 - 3rd row powerfold seat stuck down 2007 - 2014 Expedition ... 2010, 2011, 2012, 2013 and 2014 Ford Expedition and Lincoln Navigator ... I also tried lifting the seat while my wife was pushing the button to raise it, to no effect. There is defnitelypower going to the motor but it just isn't ... Join Date: Feb 2005.

No power to third row seat on 2005 lincoln navigator - Fixya

www.fixya.com/cars/t12295627-no_power_third_row_seat_2005_lincoln

Apr 4, 2012 - no power to third row seat on 2005 lincoln navigator third row seat is ... U will have to replace the entire power seat transmission, there is no ...

Lincoln Navigator Review - Edmunds.com

my third seat is stuck in the down position . press switch to raise i hear the motor but nothing happens. 2006 ford explorer

the middle seats come out easily. There are 2 handles you have to lift up on each of the bucket seats, they are in the front of the seat down by the seat tracks. After you lift them, tilt the seat upward in the front and rotate them backward. Then lift out of the hooks. Each seat is held down by 4 hoks.

The 3rd row seat is not designed to come out xcept by a technician. It does slide forward all the way up to the front seat. It has a sliding seat track.
First, lift the T handle under the seat cushion on the left front side of the seat. This will allow you to lift the seat bottom up all the way to lcok in the full up position.
Then, lift the lever on the same side of the seat and slide the seat forward. It will stop in 4 places.
Rear -Rear
6 inches forward of that.
another two ft to the second row seating position
full frward against the front seats.

Pleae rate as fixya if this helps.

Seat —Third Row Bench Removal
CAUTION: Removal of the third row bench seat requires more than one technician.

1. Remove the second row seats. For additional information, refer to Seat—Second Row .

1. Remove the floor mats.

1. Lock the seat cushion in the upright position.
   1. Lift the handle to release the cushion.
   1. Lock the seat cushion in the upright position.

1. Move the third row bench seat to the second row position.
   • Lift the seat track release handle.

1. Remove the two bolt covers.

1. Remove the two seat track front bolts.

1. Remove the four seat track rear bolts.
   1. Position the rear seat cushion floor cover aside.
   1. Remove the four seat track rear bolts.

1. Remove the third row bench seat.

check for seat belt stuck in crack between seats back and cushion.

remove seat cusion to see if soemthing is stuck. see owner manual for directions. here's explorer

Rear Seat Backrest —Third Row Removal and Installation

1. Release the two seat levers located at the lower outboard edges of the seat cushion. Lift out the seat cushion.

Its pretty tough...the headrest comes as a cassette type and a release cable that runs down the back rest of the 3rd row seat.