Installing Power Trunk Release in the '99
By Steven Kamp
Why install the power trunk release?
The power trunk release servers two purposes. First
of all is convenience. In the '99 Miata the key lock is located very
low and using the key could scratch the paint. The second reason is security.
Installing the power trunk release allows the trunk pop in the glove box to
be disabled. The '99 Miata has a plastic lock mechanism for the glove
box and is easily defeated. The kit I used was from Duetto Motors LLC
cost is $29.95 + shipping.
The kit includes the following:
- Trunk release solenoid
- Metal mounting bracket for solenoid
- Switch for trunk release solenoid
- 20 ft. green 18 Ga. wire
- 1 ft. black 18 Ga. wire
- 1 ft. red 18 Ga. wire with fuse
- 1 metal strap (not needed for install)
- Various screws
- Remove bottom trunk carpet.
- Remove the back trunk cover by removing the seven plastic
- Disconnect the key lock rod from the key lock assembly.
- Remove the two 10 mm. bolts that hold the trunk catch mechanism
- Release the manual trunk release cable from the TCM.
- Bring the TCM to a work bench.
- Remove the other end of the key lock rod from the TCM.
- Now on to mounting the solenoid bracket. The bracket fits
perfectly under the TCM. The bracket fits between two ribs in the metal. The
best way to position the bracket is to temporally reinstall the TCM in the trunk.
Install the solenoid into the bracket. Position the bracket (with solenoid)
underneath the TCM with it barely touching the TCM. The bracket needs to be almost
touching or the back trunk cover won't fit correctly. Once the bracket is
positioned, mark the two mounting holes. Remove the bracket and remove the TCM.
- Pre-drill the two bracket holes but make sure to use a drill stop so
the drill bit will not go through the trunk.
- Mount the bracket (without solenoid) using the two sheet metal screws
in the kit.
- The next step is to connect the trunk release solenoid (TRS) to the
TCM. The best way is to remove the metal adapter that is on the TRS. This
leaves only the cable. Take the cable and form a loop. Then clamp the loop
shut with the bolt and nuts that held the metal adapter to the cable. You are
going to have to play with length of the loop so the bolt and nuts fit within the
TCM. Once the proper size loop is made connect the loop to the hook that the factory
pull cable was connected. Next push the metal stop into the location where the
factory plastic cable stop was.
- The next thing to do is test to make sure the solenoid will release
the TCM. (NOTE: The solenoid only operates when the cable is all the
way out. It works by pulling the cable back in when power is applied).
Take the TCM and the connected solenoid to the trunk of the car. Temporally connect
the black and green wires to the back of the TRS. Connect the back wire to the
ground and to test tap the green wire to the positive terminal on the battery. At
this point the TRS should open the release on the TCM. If it does not you need to
modify the loop as in step 8. If it does work, test multiple times. Remember
to completely tighten the bolt and nuts that hold the loop together. This will
prevent the loop from loosening up.
- After the testing is complete and the TRS pops the TCM opens
reliably, reconnect the factory key lock rod to the TCM.
- Mount the TRS in the bracket using the two set screws in the kit and
position the cable behind the key lock rod.
- Remount the TCM in the trunk loosely using the two
10 mm. bolts.
- Reconnect the lower rod to the trunk key lock assembly. NOTE:
Make sure this is connected and working before the next step.
- The next step is tighten the 10 mm. bolts down. You may need to
adjust the height for the trunk to close properly. Test for proper height and use
the key to regain entry to the trunk.
- Now that the physical trunk release is mounted the wiring is next.
For the wiring connect the black wire to the one of the connectors
on the solenoid. Use a small self tapping screw and connect the ground to sheet
metal near the TRS. Connect the green wire to the other connector on the TRS and
route the wire to the cockpit through the left tunnel. You will need to remove the
left side plastic bucket and the left front trunk cover. Wire tie the green cable to
the existing trunk release cable. Route the green cable through the hole by the back
of drivers seat and continue to run the wire under the driver side sill. The
wire will now be up by the driver footwell. The rest of the wiring is according
to how the trunk release will be actuated. See the two wire diagrams below
for the different options.