No kick down

[Savakis]

Hello,

After carefully reading this forum's topics about kick down problems and after consulting my mechanic, I must confess that the problem presented below looks like a nightmare:

- All the cables were double checked so as to conform to the wiring diagram attached here.
- The gearbox pressure is correct.
- The car upshifts / downshifts incredibly well (in D or manual positions).
- The three-position solenoid was tested while the car was running and also while the engine was off -all 3 positions work fine (ignition on: the rod moves back / slight pedal pressure: middle position / kickdown: the rod moves forward).

Despite that all the settings seem to be correct, the car can't downshift when the pedal is fully depressed while driving with the selector in D...

Manual downshifting works fine, downshifting/upshifting also work fine in D positiion.

We also unplugged all the 6 cables that attach to the terminal block (at the left side of the gearbox) and used an external battery to test the operation of the three-position solenoid: the unit works fine.

Am I missing something here?

Would this relate to an internal hydraulic gearbox problem since it seems that this does not relate to an electric problem?
 

[Cees Klumper]

It's possible that the kickdown switch located on the floor, underneath the accellerator pedal, just isn't getting mechanically pressed down far enough (or perhaps the switch is broken). Look to see whether, when the accellerator is fully depressed, the switch is actually activated. Also, you could try, with the engine running and the transmission in 'D' while standing still, foot firmly on the brake (so the transmission should be in '2') just manually press the kickdown switch to see whether it actually shifts up into first. That last test is just hypothetical, I have no idea if it would work even with a properly functioning kickdown.

[BobH]

Hello, why not unplug the kickdown switch and link it through, there's a connector just the other side of the bulkhead, to see if the double acting solenoid activates when the ignition is on.  If it does it will prove the switch is faulty, or as Cees suggests it's not being activated by the pedal

[Savakis]

Hello, why not unplug the kickdown switch and link it through, there's a connector just the other side of the bulkhead, to see if the double acting solenoid activates when the ignition is on.  If it does it will prove the switch is faulty, or as Cees suggests it's not being activated by the pedal

Hello and thanks for your answer. The kickdown switch is operating while the vehicle is stationary with the engine switched off, it actually moves the solenoid forward, we've tested it. The same happens when I drive the car, my mechanic was driving and I was sitting in the passenger seat with the carpet removed and the tunnel window open so as to check the operation of the solenoid. The rod is moving forward when the car is moving with the accelerator pedal fully pressed -to no avail, the gears don't change...

[Savakis]

It's possible that the kickdown switch located on the floor, underneath the accellerator pedal, just isn't getting mechanically pressed down far enough (or perhaps the switch is broken). Look to see whether, when the accellerator is fully depressed, the switch is actually activated. Also, you could try, with the engine running and the transmission in 'D' while standing still, foot firmly on the brake (so the transmission should be in '2') just manually press the kickdown switch to see whether it actually shifts up into first. That last test is just hypothetical, I have no idea if it would work even with a properly functioning kickdown.

Hello, I read your answer, thanks for the interest. The accelerator pedal is fully pressed, the switch is good, it's working, no downshifts though...

[BobH]

You may have read this, if so perhaps a call to these people will help

https://mercedesdismantlers.com/16BoltInstallationInstructions.html

Also have a search for "3 position solenoid" lots of similar problems on there, they talk about checking that the modulator pressure is correct

https://www.sl113.org/forums/index.php?topic=15737.msg108247#msg108247