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'95 500SL R-129 - '96 500SL R-129 - '98 ML320 - '98 CLK320
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Discussion Starter #1
I am trying to figure out why the car will not kickdown. I took a look at the control module and all looked fine including the fuses in the back....

I did want to confuse this issue with airbag replacement..

http://www.benzworld.org/forums/r129-sl-class/1325741-1995-500sl-passenger-airbag-replacement.html

Fuse number 6 and the "B" fuse are also ok in the fuse box.

Transmission fluid was just changed and the filter.

I noticed this wire(see pic) has nothing connected to it-is this normal and what does it do?



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Your transmission has no overdrive.

The kickdown solenoid is activated by one of two parallel cicruits. One is via the "B" switch on the transmission which causes a downshift from 2nd to 1st gear at rest. The other is the kickdown switch behind the gas pedal. The "B" switch receives power from fuse #6 in the main fusebox; the kickdowns switch receives power from the Base Module located in the module compartment within the engine compartment. The Base Module has several fuses mounted in its top side which you may want to check.
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2003 SL500, 2003 SL55, and four R129s
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I noticed this wire(see pic) has nothing connected to it-is this normal and what does it do?
I don't recognize that connector, but I'm sure it has nothing to do with the kickdown circuit.

I would remove the connector to the kickdown control solenoid valve and check if it is receiving power (picture). For this the key should be ON and the gear selector should be in the "B" position.
 

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'95 500SL R-129 - '96 500SL R-129 - '98 ML320 - '98 CLK320
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Discussion Starter #3 (Edited)
Your car has an old-fashioned hydraulically-controlled transmission with no electronic intelligence, and so it communicates with no other systems. The once possible exception, if this qualifies as "communication", would be the overload switch that is wired from the transmission to the ignition control module.
thanks, i will check the solenoid valve connector and see
 

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92 600 SL (LPG), 94 Subaru Impreza,02 Maserati 4200GT,97 Suzuki TL1000Sv, 02 Yamaha Fazer 1000
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We had to replace the kickdown solenoid on Jeff's car to get his kickdown to work. The solenoid comes in two parts, it's the external "coil" part that goes and needs replacing. It is dead easy to replace, a single bolt goes through the solenoid, disconnect the wire, undo the bolt, replace the solenoid, do the bolt up and reconnect the wire. If you can do it with the back of the car raised higher than the front you "may" stop the automatic transmission fluid leaking. Otherwise be prepared to swap the old and new solenoids quickly and the loss of fluid will be minimal.
 

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'95 500SL R-129 - '96 500SL R-129 - '98 ML320 - '98 CLK320
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148 Posts
Discussion Starter #5 (Edited)
I am getting 5 v power when ignition on and shifter in "b" position at the this connector(see pic)...so i guess it is the solenoid?

I have checked 3, it seems to work fine and also 2b on the shifter..

If you have a more detailed explanation of changing the external solenoid, I would greatly appreciate it...

I am also noticing the the gear slip for a second when the car is cold as it shifts from 1 to 2, then this goes away and shifts normally. Passed by Stealer and they said that they use dextron 3 quaker state in all pre '97 cars with dipstick, when i wanted to purchase the mb atf fluid.
 

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92 600 SL (LPG), 94 Subaru Impreza,02 Maserati 4200GT,97 Suzuki TL1000Sv, 02 Yamaha Fazer 1000
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You can't really do any more detailed instructions than those above! The solenoid is where you detached the cable at Y3 in the picture above. Disconnect the wire, look at the solenoid it attached to and you will see a bolt head sticking out of the end. Can't remember what size it was, 13, 14 or 17mm possibly. Undo the bolt. When you take the bolt out and remove the solenoid housing transmission fluid will leak out of the hole, but if you can jack the rear of the car higher than the front this will be minimised. Either way have the new solenoid housing ready to go straight back in, put the old bolt through the centre and tighten. Re-attach the cable, let down the jacks, all done in ten minutes. We went down to a local garage and borrowed his ramps on a Saturday afternoon that made life a lot easier. Gave the owner (who I know) a few quid for the lend :).
 

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That looks a different location to the one shown at Y3 above. The kickdown solenoid is accessed from the rear of the gearbox, the bolt is above the cross member shown in the picture to the left of "Y3"
 

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Discussion Starter #9 (Edited)
I am receiving power at the "y3"connector. I removed the plastic connector having checked in "B" & "2". "D" had no current. I am also noticing the slip between 2nd and 3rd getting more apparent before car gets warm, but it still goes away...
I guess I will order the external solenoid-or do you think these two issues are related and I should have MB check it out?
 

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1998 Pano SL500; 1993 SL500; 2005 ML270cdi
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Before buying a new solenoid have you disconnected the cable and tried applying 12 volts directly to the solenoid to verify that it is faulty?
 

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Discussion Starter #11
not so sure...having applied the gears..."b" seems to work, "2B" also works, only the "kickdown" is not working....how does one apply 12v to check in normal operation?
 

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1998 Pano SL500; 1993 SL500; 2005 ML270cdi
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Discussion Starter #13 (Edited)
Replaced Solenoid...It worked!

I replaced the solenoid. From rest the car is more responsive to the first gear start when in D and gas button is pressed...but there was still no downshift during cruising at the time of replacement...

However, the following morning when i tested the car-by some miracle, all kickdown functions were working at any speed. woohoo!

On a separate note, i noticed atf fluid on the floor...could i have overfilled it and is there an atf overflow?
 

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'95 500SL R-129 - '96 500SL R-129 - '98 ML320 - '98 CLK320
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Discussion Starter #14
Car is back to Normal

the gasket was changed at the dealer-and all is back to normal.:)
I guess when they changed the filter and fluid they must have put a bad gasket at the Bavarian motorsport in kennet square, PA. Will take that up with them.

Thank you all for your help
 

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1998 Pano SL500; 1993 SL500; 2005 ML270cdi
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Glad to hear that all is well again.

Illegitimi non carborundum :D
 

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1994 SL500
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to expand on this:
I have had similar problems with my car. The transmission was rebuilt recently, and the kickdown solenoid is getting power in 2 and B. If I downshift to B at a stop, I can tell it starts out in first but quickly shifts through all the gears and has bad acceleration. I replaced the kickdown switch, but flooring the gas pedal does not make the car kick down. Is the kickdown sitch wired to something in the center console? I will open everything up and check for loose wires. Is there anything else that I can check that would cause these symptoms?
 
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