Quote:
Originally Posted by scottmcphee
Odds are good the window control switch on the rear door needs attention. The center console switches for window control rely on good contact in the door switches themselves because power is routed through them while resting in their neutral position in order for central switches to have an effect driving the window motor.
If you disconnect / unplug the window switch in the door, the center console switch cannot drive the window up or down. That's just how things are wired.
Trivia: anybody know what will happen (without trying first) if the driver and passenger have a tug-o-war over the passenger's window by using switches in opposite directions? Keep in mind this is an old German car.
Is it:
A) the driver command always wins and overrides the passenger every time
B) the passenger overrules the driver's command every time
C) the driver command causes the passenger command to pause (halt) the window, then the first to let go is the loser, whoever holds longer eventually wins the window going in their direction
D) if the driver started the action the passenger's attempt is thwarted and driver's chosen direction keeps on truckin' and vise versa for the passenger if they started first
E) so long as either switch is in the down position the window keeps rolling down
F) sparks fly or a fuse blows if you're lucky, you just put 25Amps through two switches and created a dead short
G) the motor conjigulates as it tries to satisfy both commands simultaneously, and depending on the state of lube of the window regulator the window may slowly creep up, or down at a fraction of the normal speed
H) all doors unlock if they were locked, but the trunk and fuel door remain locked, and interior lighting goes on
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it is answer C
The switches have a clever slip contact arrangement on their two contacts.
In the driver switch, the slip contacts have 12 V applied.
One slip contact is made in the "up" and "rest" position to the moving contact, and in the "down" position the moving contact touches a grounded contact point.
The other slip contact works the opposite way, the moving contact has 12 V on it at "rest" or "down" and is grounded for "up".
Hard to explain without looking at a diagram but here goes. If you have a diagram it is easy to follow the paths.
Switch at rest, both contacts pass 12 V to the motor, since both sides of the motor have 12 V applied, the motor does not run,
Switch in "up" position, one contact applies 12 V and the other contact applies ground. The motor runs since there is now potential across it.
Switch in "down" position, one contact applies ground and the other applies 12 V so the motor runs in the opposite direction.
The rear switch has the moving contact lines from the driver switch applied to its slip contacts. The moving contacts of the rear switch connect to the motor. The rear switch does not see 12 V directly, only the switched lines from the driver switch. The ground points on the rear switch are brought back to the console, but are interrupted by the child lockout switch, so if the child switch is open, the rear switch lost its ground, but the front switches still have a ground. So the parent can operate the window but the child can not.
The passenger switches are arranged so that if they are at rest, the voltages from the driver switch pass straight through the two slip contacts on to the motor. If the passenger switch is moved, one of the motor leads gets grounded and the other has 12 V.
If both switches are at rest, both legs of the motor have 12 V on them. Nothing happens.
Both switches moved in the same direction, motor runs in intended direction since the slip contacts apply ground (locally) and the 12 V from the driver switch to the motor.
Both switches moved in opposite directions, both ends of the motor winding have ground applied - no motion. No sparks, no drama, no blown fuses.
Wikkid Smott as they say up in New England.
This is true for 123, 124, and both generations of the 126.
Once you get to the 140/210 it is all on CAN bus and the door control module logic prevents this sort of conflict.