I own an old Daihatsu Charade and my hatch strut (or door stay to others) is malfunctioning as it no longer hold the weight of the hatch as it drops down as soon as you take your hands after lifting the hatch. As a result, I always placed my steering wheel lock to hold the hatch in place.
The solution? A piece of PVC. I first measured the shaft after its fully stretched, then cut a PVC with the same measurement minus an inch. Then saw the middle of the PVC for at least 2.5mm to snug fit it to the shaft of the strut.
Just place the pvc between ends of the shaft to hold its weight, and slide the pvc to the strut when your closing the hatch.
With this cheap and hassle-free fix, I can now enjoy lifting my car’s hatch and no more worries that it would drop on my head anytime haha!