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· Banned
Y2K SL500 Silver
8,710 Posts
Discussion Starter · #1 · (Edited)
The posts below are organized by the year of the car.

First Group>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Function Description of Roadster Soft Top and RST Troubleshooting PDF's

The soft top control system is surprisingly simple. The controller executes a step-by-step sequence of motions as illustrated by the document

96 SL and later cars require a M-B STAR Diagnostic System scan tool in order to check for DTC's and reset controller

99 SL codes were reset for $40.00 at the Dealer because Soft top was stuck down and roll bar stuck up!

***Remote Soft Top controller p/n's and repair/rebuild facilities UK rebuilds your control module for $375 plus SH and they give you a warranty.

R129 remanufactured soft top control modules for $375-$715+tax+ship vs. $1360.00 at the Dealer

All Power Top Control Modules are $595 and come with a two year warranty.

Attached is a picture of the circuits from an early version of the control module

SL soft top control unit location

00 SL soft top control unit location

To remove the hard top you have to operate the switch within 10 seconds of turning the key on and the windows have to be down

00 SL soft top stuck in compartment

00 SL check the state of all of the limit switch inputs to the controller, controller holds information up to one hour

97 SL windows won't synchronize due to a defect either in both window motor units or the soft top controller


97 SL soft top controller probably is not getting the signal from the left door switch

97 SL discharging when the car is off

97 SL red button stays flashing

97 SL Central Locking not working

1997 S84/4, "reed magnetic contact switch" sits in the windshield top cover

*97 SL battery lost charge>then recharge>now red soft top and rollbar light permantely>means diagnostic codes need to be reset by Indy or Dealer

1996 Fixing the bow extension micro switch

*96 SL and later with a fault in your soft top controller which can only be reset with and advanced diagnostic tool

*96 SL and newer cars need a scan tool to reset codes, go to Indy or Dealer and ask how much to reset the soft top codes

*96 SL go to the dealer or a mechanic who has the proper tool and have them read and clear codes in the soft top controller

*96 SL soft top controller controls the roll bar on '96 and newer cars

How to reset the roll bar after it has been deployed.

How to adjust and/or reinstall the roll bar sensors

MY 93 and newer picture of 38 pin plug under the hood/bonnet of a RHD car

Second Group>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

95 SL windows must also be "synchronized", as explained in the owners manual

95 SL controller is not receiving the proper inputs telling it that the top is completely closed/open

94-95 SL There are just 10 diagnostic codes instead of 29

*R129 diagnostics through model-year 1995 and codes

*90-11/94 SL how to read diagnostic codes by Bob Terry

*SL Soft Top Controller Reset and Roll Bar Codes and Reset Procedure

94 SL soft top will not complete an opening or closing operation unless both windows are lowered

?? SL roof stuck under the bonnet!

?? SL diagnostic socket in the passenger footwell. You only use this to put the top controller in a special diagnostic mode which evaluates the limit switches

94 SL top closing operation stops because the passenger window has not lowered

Third Group>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

93 SL soft top won't open/retract

93 SL Convertible top cannot complete its cycle

93 SL has a problem when opening soft top

92 SL Convertible top

You don't synch the windows on an early SL

92 SL roll bar and soft top stopped while going down

92 SL and I don't know what is wrong with the soft top

92 SL limit switch located in the bottom of the door

92 SL ASR light always on and the Rollbar is coming up by it self when im driving i cannot release my hardtop automaticly

*91 SL method of clearing and reading the soft top codes

91 SL I wouldn't do anything without reading codes for the top controller first.

91 SL are you activating the release switch within 10 seconds of switching the ignition to ON

91 SL indicator lamp will not stop blinking along with the audible warning

91 SL how to verify that all inputs from the various limit switches are working properly

91 SL cleared ALL codes AGAIN, disconnected the controller and cleaned all pins and sockets with electrical spray

*91 SL Reading codes is simple and all you need is a wire or a paper clip to use as a jumper

90-91 SL soft top problem

90 SL Front top latches don't close

90 SL everything is latched properly but the switch is still lit, then one of the microswitches isn't signaling the controller

90 SL soft top problems

R129 soft top 'Hydraulic System' ultimate thread

· Administrator
1998 Pano SL500; 1993 SL500; 2005 ML270cdi
9,660 Posts
Just for reference this is the hydraulic pump that supplies the fluid to the operating cylinders.
It is located in the trunk under the plastic covering that the spare wheel fits on to.
There are Max and Min fluid marker lines which are about 2.54cms/1" apart.
The reservoir in the photo is filled to the Maximum level.
Note: entire system holds 1.25 Liters of fluid

1993 SL pump (top pic) and 2000 SL pump (bottom pic)


· Registered
129 sl 1999
1 Posts
soft top probs 99 320 sl 129

Can anybody help up to the pass window regulater going faulty the roof worked fine Replaced regulater now the rear plastic window section does not close ALL WORKS FINE WHEN OPENING. if you push it down it does lock into place but the red light stays on and you get a bong for ten secs when driving. . the windows do not work in the closed positon

· Administrator
1998 Pano SL500; 1993 SL500; 2005 ML270cdi
9,660 Posts
morriswu said:
Hi RedLiner,
How do you think the color of the hydraulic fluid? isn't it dirty?
I'm not sure what the brand or grade of hydraulic fluid is, however (touching every piece of wood in sight) it stays up to level and none of the cylinders leak.
It's probably just the colour of that brand of liquid because I can't see how dirt could get into the system.

I got a full service history when I bought the car with every service record and all receipts for work carried out. I'll browse through it all and see if there is any record of the soft top hydraulics just out of interest.

· Outstanding Contributor
2005 SL600, (2) 2003 SL500
4,604 Posts
maxwellgolf said: the rear plastic window section does not close ALL WORKS FINE WHEN OPENING. if you push it down it does lock into place but the red light stays on and you get a bong for ten secs when driving.
I would guess that the soft top compartment cover is not closing completely; or if it is, the top controller is not being signaled. The signal comes from a switch on the right-side latch (picture) that is wired to the #7 socket of the large electrical connector on the top controller. It should short to ground when the cover is closed. You can check that with a basic multimeter, an LED, or test light, etc.


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