How to Reset your Hentronix Mechanism (for all units with a Long Screw and Arm)
First, disconnect the battery and put the split pin back to connect the door to the arm. Then, using a 13mm or adjustable spanner, turn the brass connector at the motor end of the thread until the door is about half open (mid position). It's a bit slow and tedious doing this but it allows everything to reset.
Then, reconnect the battery. The blue LED should light for 1 second, then there is a short pause, then it will either open or close depending on where it left off previously. If it is daytime it should either open and stay open until dusk, or it will close and then open after one minute.
If there are two nuts with a split washer in the middle on your unit, moving them towards the compressed spring (loosening, moving, tightening back up again) will help prevent this in the future! This applies to Original Hentronix units, and also the large MK1 Eglu Cube units (full opening/closing capacity). If it is a Compact Horizontal unit, please consider putting in a hard 'back stop', such as a baton of wood so that the door is stopped hard in its path before the spring compresses too much.
The reason this happens is that we need to program the unit to allow for an 'average' weight of door. Over-compressing can happen when the door is lighter than expected - but the measures above will absolutely solve the problem. Please get in touch with us if you have any other questions about this!