Solving Power Trunk Release Problems

When it comes to modern automotive accessories the convenience and low cost of a power trunk release makes them widely available on many models regardless of age. This article explains basic operation of the system and explores how to prevent and repair problems.

Power Trunk Operation

The power trunk release on most cars is a very basic system consisting of only a few parts. These are commonly an electrical switch that activates a release solenoid. The circuit is completed by closing the contacts on the switch and allowing battery voltage to energize the solenoid in turn pulling a retractor rod that physically releases the latch allowing the trunk to open. The trunk usually lifts to the fully open position thanks to a pre-loaded torsion bar or coil spring that’s engineered to overcome the total weight of the trunk lid. These springs can be found near the hinge and the tension is often adjustable. This adjustment can stop the trunk lid from flying open violently while still having enough tension for the lid to pop up when the solenoid releases the latch. Trunk lid springs are also able to compensate for installed accessories such as rear spoilers.

Remote Trunk Release Vs Power

A remote trunk release is very different from a power one. The latch is physically released by a manually operated cable that runs from the release lever mounted inside the car often conveniently located next to the driver side seat. Although these types of releases are much more reliable they aren’t as convenient because they cannot be activated from a key fob remote control without the addition of some type of solenoid to move the cable.

And although unusual it is still possible to run into troubles with a manual trunk release. The cable can stretch, bind, break or become out of position, so it doesn’t pull on the latch properly. Problems with a manual trunk release are easily diagnosed with a partner that can operate the lever while the technician inspects the movement of the cable back at the trunk latch. Manufacturers now include an additional emergency release that can be operated from inside to prevent people from getting locked in.

Problems with Power Trunk Systems

When it comes to the evolution of the power trunk release this is surprisingly, one automotive accessory that continues to evolve and go through some changes in an attempt to improve the usability from a driver’s perspective. One of the main problems when closing a large trunk lid is the air trapped inside can prevent the lid from properly latching. This can lead to a lot of trunk slamming which greatly increases the wear and tear on the latch mechanism, power release solenoid and striker. General Motors took an interesting idea, later adopted by other manufacturers and made it a reality on their late 80s model cars. The invention was an all-inclusive power trunk release that contained a switch, solenoid, latch and a steel slide operated by a motor that provided an automatic pull down feature.

GM Trunk Pull Down Operation

The General Motors trunk pull down system solved the problem of air displacement preventing the trunk lid from closing easily. In celebration of its effectiveness the General started installing the power latches on popular models that could benefit from the technology. When the release was activated the motor ran the latch up and when the trunk lid striker was gently pressed against the reverse run switch the motor pulled it down to the fully closed position automatically. Although a fantastic idea to deal with the air resistance problem in large trunks it was wrought with problems.

One root cause of issues was the customers weren’t instructed on its proper use. They were surprised and confused by the new feature, even after it had been around for many years. As drivers continued to slam the trunk or hatch lid against the delicate motor, latch and switch combination, these parts quickly began to malfunction. Since many of these automobiles are still around complete trunk latch assemblies are still available as replacement parts.

In conclusion, sometimes people have problems with their power trunk release systems because they close them too hard. I have seen some drivers jump up and grab the trunk and pull it down like they were spinning the giant wheel on the Price is right. A slower swinging of the trunk lid will allow air the time needed to escape from the enclosed area facilitating the proper closure. Since old habits are hard to break, some manufacturers like Mercedes-Benz have gone a step further by installing power door assist. This is an automatic ventilation system that quickly vents cabin air outside making it easier to close both doors and trunks.