Use the trunk popper switch! If this switch does not work then use needle-nose pliers or a paper clip to momentarily touch the two pins on the switch's connector which are vertically adjacent to each other. If there is a dead or missing battery then a very long flat tip screwdriver can be used to manually turn the latching mechanism which the lock normally does.
P.S if that does not work beat the living crap out of the lock, they are very tough so expect a long fight
The lock has a clip on the inside, pull the clip off and the lock will come out, remove the lock rod and then you can use a screwdriver to open the lock.
there is open trunk switch in the glove compartment
With the lock mechanism missing, look into the hole where the lock should be. Take a flat screw driver and insert it into the slot near the back of the lock hole and twist.
Remove rear seats
The rear "trunk" (decklid) release mechanism is an option, if equipped, and is located on the right side of the dash protrusion on the dash. It will be a switch that shows an opening "trunk". If this switch is not there, then the car was not equipped with rear trunk release. If you are trying to get into a Fiero trunk that does not have a decklid release mechanism or a broken one, and you have lost the keys, then you will have to actually break into the car to open the trunk. Typically, if the outer key switch is remove, you can insert a long screwdriver into the hole and pop the trunk lock.
May have to remove rear seats and get in from there
It is manual, there is no trunk button whatsoever on the inside of the car, you need the key to get in. The lock on ours was broken, so we had to drill through the destroyed lock to open it :D
I have an buick regal custom 1992 and in my glove box there is a trunk release button. yellow. Not sure if this is a standard
how do i replace a trunk lock with another lock that has a key
Unfortunately, you are in a bad situation. I am assuming that your Fiero is equipped with the decklid release button, where you can push it and the decklid opens and you don't have a key. First, call a locksmith over and have them make a copy of the key for your doors. Expensive, but the safest. The decklid lock and your door locks SHOULD use the same key, unless someone has changed them out over the years. The second option is that you will actually have to break into the "trunk" (decklid). This can be done by removing (destroying) the outer portion of the lock and removing it. Inserting a long flat head screw driver into the hole, working it in, and turning it will pop the trunk. Unfortunately, you will have to do this everytime to open it or replace the lock. The only other option you have is that you can sometimes 'jump' the solenoid for the trunk release from under the car. I unfortunately do not remember it's exact location, but wiring diagrams are available online. If jumped from a fresh battery, you can pop it and it will open. Source: Fiero owner for ten years.
On my 1992 190E I can lock the trunk with any of the keyed locks. If you lock the doors, the trunk locks and if you lock the trunk, the doors lock. In other words all the keyed locks are electrically interconnected. In reality the locks are not electrically interconnected. There is a pump in the right side wheel well of the trunk, it uses vacuum to lock all the locks and pressure to unlock them. Although the pump is powered electrically, the locks are not.
* Remove the trunk lid latch * Detach the lock release box from the latch assembly * To detach the lock cylinder from the trunk lid pry off the retainer