The lock on the hatchback will not unlock when the weather gets very hot and the car is parked for about a half hour the other locks pop up but the back wont budge the car is a 2000 MERCURY SABLE WAGON

call tow service ask weather they have lock out service and tell them to bring lock pick tools.

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Read manual. It should direct you to location where you can manualy unlock hatch. Look for little trap door. It should be located very near lock.
Hope this would help

does this help? look in owners manual for how to turn "on or off" the auto lock feature.


Automatic Door Lock/Unlock
The automatic door unlock function is a vehicle personalization feature with the following 3?programmable modes of operation:
1. All: All of the doors will automatically unlock. 2. Driver: The driver's door will automatically unlock. 3. None: The doors will need to be unlocked by a door switch command or by pressing the the lock button on the RKE transmitter. The All or Driver modes may also be programmed as to when the automatic door unlocking will occur.
1. Key Off: The door(s) will unlock when the key is turned off. 2. Shift to Park: The door(s) will unlock when the vehicle is shifted into P (Park). The delay lock function may be enabled or disabled. When the function has been disabled, the doors will only lock by a door switch command or by pressing the the lock button on the RKE transmitter. When enabled, the doors will not lock until five seconds after the last door is closed.

Hi
Most likley the lock is sticking, once you get it open get some grease spray or WD40 spray inside the lock mechanism while using the remote to lock and unlock. do this many times as you are spraying the WD40 make sure you really get into the mechanism, you should get a small straw with the WD40 attach this and get inside the lock as much as possible. this is very common and often occurs wheen the weather goes from hot to cold or vice versa.

Also spray the lock hook part, this is the part the mechanism attachs to once shut. if this does not fix the problem the lock hook, may need to be adjusted, they often have 2 screws or bolts you simply half loosen them and re - align them. If you need more info on this please let me know
Regards
Dan

check engine coolant temp sensor, its detect engine overheats that command the computer to engine shutdown for protection, try to replace a good one

Sounds like a dodgy central locking motor, I would first though
get some wd40 and spray all the locks and inside the mechanisims, they sometimes get stiff in cold weather and when they lock they dont go all the way to the lock position leaving them half way either way, hence the doors lock and unlock. It may be the motor itself but try this first as it will save you a few quid.

let me know if you need instructions on how to remove the central locking motors.

Regards
Dan

Unsurprisingly, it is the cold. Sit a blow heater on low ( less than 1kW) pointing at the boot lock area for half an hour or so. Then it works - for a while. I think the lock motor gets weaker with age, and then the freezing cold makes the various joints that are greased just 'wax up'.

The combination is what does it. Also, sticks the boot lock in the open position, even worse. SOLUTION: NEW LOCK. Mine lasted 4 years, until now. Or wait til warmer weather. Or remove interior panel and wd40 all linkages, motor spindle etc. This will probably fix it, but for the sake of a £15 unit, I dunno.

It sounds like your lock actuator is dying, or something is jamming up.
If your car is a 2008, then this should be covered under warranty to fix.

If you do want to fix it yourself, you can. On the inside trim, you can remove screws that are by the door handle, arm rest, under door and side of door and then gently pull back on the panel as there will also be retaining clips attached and you don't want to break them. You'll need to lift the door panel upwards in order to get it off the window ledge. Then you'll need to manipulate the panel and disconnect the door handle linkage from the door handle and disconnect the wiring for your controls. Pull back the weather seal and you can access the inside of the door

It may be runnig to hot, try to change the thermostat for a colder one and try it.

The park lights staying on indicates the switch is deteriorating.
I would replace it.
The door locks is probably a voltage issue. With the cold weather, the locks need more voltage to unlock. They get that voltage when the engine is running. If you really want the locks to work without the engine, you might try accessing the locks and cleaning them. Then use a lightweight grease, like lithium grease, to help them open with less power.