There seems to be a new problem. My rear hatch release motor is constantly running with the key in the start or car running position and a door open. It took me the better part of today to figure out that the top screw for the above mentioned plastic piece went through a bundle of hot wires.
What threw me off was the second task of adjusting the e-brake cable because of the rear hatch release electrics I had to unhook.
Hope this helps with some of your electrical problems. It could have easily been another or more wires.
The way the hatch release motor works is a little non-intuitive.
It runs for 2 quite separate reasons:
1) The initiation circuit
2) The parking circuit
The initiation circuit is fed by the interior light supply, via the hatch pull switch (es) to the motor and the motor ground is via the switched interior light switch ground.
To operate correctly the following have to be working:
The interior light fuse
The hatch pull switches
The interior light switch ground must get connected to ground
- a. the interior light door switches must trigger the (delay) relay switching
- b. The rear hatch switch (open) drives this with a direct switch drive
If any of these are not functional your hatch switch (es) will not initiate a release cycle.
The interior light "feature" ensures you can only open the hatch when a door is open - so its locked out when you are normally driving.
The motor will continue to run for as long as you pull the hatch switch - but without any other circuits operating the hatch motor will stop as soon as you let go. It may stop at a point where the hatch cannot be latched closed...
The parking circuit is rather simpler - it is designed to run whenever the motor is not in its park position - its sole purpose is to cause a motor cycle - once initiated as above - to continue all the way to the park positions (hatch unlock tab in the fully disengaged position). When it gets to this point it stops driving the motor - of course it will keep running if you are still pulling a switch.
It accomplishes this with an integrated circular track with a wiper driven by the motor and a break in the track at the park position. You can see & clean this easily if you disassemble the motor.
The parking circuit - only - is fed by the dedicated 1A fuse on the CE (fuse) Panel.
If that fuse is bad your motor will stop as soon as you let go the hatch switch, if your motor continues to run cycles after you release the switch - your circular track has likely become continuous across the gap from smearing - usually cleaning restores operation.
The switch tops spin off the body anticlockwise. Some seem to have issues with these - there is a little lock hole in the side. All mine have always come off with a sharp twist to initially break them loose... and no need to use the lock hole. I don't think you need to remove them though - focus on the interior lights.
1994 928 GTS Black/Black Manual "AZ Desert Gang"
My hatch release opens the hatch perfectly but as soon as I release the
button the motor stops, it doesn't return to the rest position. So if I don't
hold the switch the right amount of time the motor stays in the released
position and the hatch won't latch shut. So then I go back and pull the switch
for a second or two and then I can properly close it.
Is this something in the motor that can be repaired?
Check fuse #24 if 87-89, or #25 if later, assuming you already checked #26 which is main fuse for Hatch release.
The mechanism is similar to the headlights. The system is activated and starts to run by a 12v pulse which starts the electric motor. That is what you do when you pull the release switch next to the driver seat. It is a temporary 12v which is only the startup power.
Over a separate power connection another 12v is applied which fees power to a disc with a contact strip. the contact strip picks up 12v after startup and while the mechanism turns, thus feeding the motor. At some point the disc has a cut in the copper conductor, a dead zone, and the contacts then do not get 12v applied. Thus the motor stops and the system is in rest again.
What sometimes happens is that grease with copper grind residue settles in the dead zone and makes the system continue to run. Another cause is that the system runs so smoothly that the inertia of the system makes it overshoot the landing zone and starts making another round.. and another and another.
The gearbox with the copper disc can be opened and checked. Cleaning it up and adding plenty of non-acid grease will help.
ps: also check out the page called power flow for the hatch motor. That explains the wiring and fuses.
1992 928GTS midnight blue