Mercedes-Benz Forum banner

1 - 20 of 103 Posts

·
Registered
Joined
·
57 Posts
Discussion Starter #1
Soft top and roll bar both are not working and I can't read codes from RST module via OBD1. I have 1990 R129 500SL with 16 port OBD1 diagnostic socket. I recently bought R129 from US for restoration project. When ignition on, position 2 (engine not running) the soft top alarm is on (sound), no light on soft top power button S84, pushing the soft top power button nothing happens, the same for roll bar button, however both windows work fine. So there is some juice in RST module. Fuses seams to be ok. Previous owner said he sent RST module to be repaired 1,5-2 years ago and paid 500 dollars and got it back fixed, but the soft top did not worked anyway.

I built code reader myself. It works, I was able to read codes from all the sockets except 10 which is for the RST module. When I push the code reader button, then code reader light lit up for 2-3 seconds as it should (also S84 button lit up) but after that nothing happens no flashing lights, nothing, so I can't diagnose RST module.

I checked the power coming to RST: power on X12 and Z11 on both was 11,5V and ground on X10 which had solid ground contact.

RB module is responsive and have 5 errors: codes 4, 5, 6, 7 and 8.

I have read many threads for days and can't find solution to my problem, therefore I'm starting new thread in hopes someone can help. Please help!
 

·
Outstanding Contributor
'03 SL500, '03 SL55, '97 SL320, (2) '91 300SL, (2) '91 500SL, '00 S500 -- all for sale
Joined
·
4,173 Posts
I'd begin by investigating this:
When ignition on, position 2 (engine not running) the soft top alarm is on (sound)...
The software in the controller is reading that the vehicle is in motion, but of course it is not. To discern whether the problem is internal to the controller or is with the speed signal, I'd see what speed the climate control unit is reading from the signal. For that use "Test Mode A" as explained in the diagnostic manual.
 

·
Registered
Joined
·
57 Posts
Discussion Starter #3
I'd begin by investigating this:
The software in the controller is reading that the vehicle is in motion, but of course it is not. To discern whether the problem is internal to the controller or is with the speed signal, I'd see what speed the climate control unit is reading from the signal. For that use "Test Mode A" as explained in the diagnostic manual.
Thank you for your guidance. I tried step by step, but climate control does not go into Test mode A. Ignition ON (engine not running), then I press "rest" and within 1 second press blower speed button 4. Climate control temperature display still shows temperature. I tried to enter into B and C test modes, but climate control does not go into these modes also. What would you do next?
 

·
Registered
Joined
·
57 Posts
Discussion Starter #4
I'd begin by investigating this:
The software in the controller is reading that the vehicle is in motion, but of course it is not. To discern whether the problem is internal to the controller or is with the speed signal, I'd see what speed the climate control unit is reading from the signal. For that use "Test Mode A" as explained in the diagnostic manual.
I'm starting to think that may be REST button on climate control is not working. Any other button i push on climate control red light lit up (for the button), but for REST it doesn't. From which module climate control is getting data to show for Test A, B and C?
 

·
Outstanding Contributor
'03 SL500, '03 SL55, '97 SL320, (2) '91 300SL, (2) '91 500SL, '00 S500 -- all for sale
Joined
·
4,173 Posts
Some very early controllers may have no diagnostics.

If your instrument cluster can be removed with no fuss, then remove its two round electrical connectors and see if that kills the alarm. If you can't remove the cluster, you'll have to do a voltage measurement of the speed signal. I'd have to check what you should expect.
 

·
Registered
Joined
·
57 Posts
Discussion Starter #6
Some very early controllers may have no diagnostics.

If your instrument cluster can be removed with no fuss, then remove its two round electrical connectors and see if that kills the alarm. If you can't remove the cluster, you'll have to do a voltage measurement of the speed signal. I'd have to check what you should expect.
I think I can remove instrument cluster, since I'm doing restoration of the car, I'm taking it step by step apart anyway. I would be happy to do also voltage test on the speed signal. I read or saw somewhere that speed signal is in hertz?

Also I wanted to ask should soft top be working if both seats and seat control modules under the seats are taken out? Soft top and roll bar was not operational when I had the seats in the car, but now I have taken them out and also all of the interior trim. Just wondering would that be a problem for testing and getting soft top and roll bar operational?
 

·
Outstanding Contributor
'03 SL500, '03 SL55, '97 SL320, (2) '91 300SL, (2) '91 500SL, '00 S500 -- all for sale
Joined
·
4,173 Posts
When the vehicle is moving the speed signal is a DC pulse train with a frequency more or less proportional to the speed.

If you remove the connectors to the cluster, try both operating the roof and reading codes from the controller.

If the seats are removed the roll bar and roof operation should be unaffected, though there will be faults set in the roll bar controller.
 

·
Registered
Joined
·
57 Posts
Discussion Starter #8
When the vehicle is moving the speed signal is a DC pulse train with a frequency more or less proportional to the speed.

If you remove the connectors to the cluster, try both operating the roof and reading codes from the controller.

If the seats are removed the roll bar and roof operation should be unaffected, though there will be faults set in the roll bar controller.
I removed the instrument cluster, removed two round connectors to it, the rest of the connectors I left connected. Alarm from dome is still on. Soft top power switch (S84) did not lit up when turned ignition on. Roof with s84 not operational, nothing. Tried to read codes from 11X/4 socket 10, no feedback, no flashes. The only feedback, is the S84 switch lit up when code reader's button is pushed, after release of code reader button nothing.

I read voltage for vehicle speed signal input on Y connector to RST (without lifting the car and turning the wheel). On Y9 I got 0,05V and on Y35 I had 7,05V (both round connectors to instrument cluster was unplugged).

Any ideas? Does that voltage seems ok?
 

·
Outstanding Contributor
'03 SL500, '03 SL55, '97 SL320, (2) '91 300SL, (2) '91 500SL, '00 S500 -- all for sale
Joined
·
4,173 Posts
On Y9 I got 0,05V and on Y35 I had 7,05V (both round connectors to instrument cluster was unplugged).
I would have expected something different on Y35, but it could be correct.

If you plug the connectors back into the cluster, read those voltages again, and report back, I can compare to what my car measures.
 

·
Registered
Joined
·
57 Posts
Discussion Starter #10
Thank you Mr. BobTerry, you have been real help on this and other threads! I will do that and get back to you. Meanwhile I have been trying to to go through circuits of the RST. I read your recommendations on other thread for those who want to try to repair RST himself there are two common things power, including zener diode and the 3 capacitors around it. I checked them out and they are fine. The other thing to check and actually due to the fact that is difficult to check, better to replace both SA5090D chips. I'm not sure that change of SA5090D chips will help my case, I read that they are responsible for providing analog switch input into microcontroller. And at the moment I'm not having problem with part of the roof operation, but it is not working at all. It seams that chips are not getting power and I'm thinking of replacing ZTX 751 transistors. What do you think of that? May be some other things I could check, replace on RST?
 

·
Outstanding Contributor
'03 SL500, '03 SL55, '97 SL320, (2) '91 300SL, (2) '91 500SL, '00 S500 -- all for sale
Joined
·
4,173 Posts
...on Y35 I had 7,05V...
On my car I get 10.5 volts DC with the instrument cluster plugged in.

The other thing to check and actually due to the fact that is difficult to check, better to replace both SA5090D chips.
Those chips are relay drivers which interface the microcontroller to the assorted relays. They aren't difficult to test. A binary code applied to 3 pins selects an output to energize.

It seams that chips are not getting power...
All of the chips should have around 5 volts powering them. That is the next thing I would check.

Since the alarm sounds, presumably the controller isn't recognizing that the top is locked down. I'd check the limit switch inputs to determine if the top is not locked or if you have a problem with the controller reading the switch inputs. A procedure for checking the switches is here: https://www.benzworld.org/threads/soft-top-gets-stuck-going-down.2665913/#post14684122

I would not be inclined to replace any transistors at the moment.
 

·
Registered
Joined
·
57 Posts
Discussion Starter #12
On my car I get 10.5 volts DC with the instrument cluster plugged in.

Those chips are relay drivers which interface the microcontroller to the assorted relays. They aren't difficult to test. A binary code applied to 3 pins selects an output to energize.

All of the chips should have around 5 volts powering them. That is the next thing I would check.

Since the alarm sounds, presumably the controller isn't recognizing that the top is locked down. I'd check the limit switch inputs to determine if the top is not locked or if you have a problem with the controller reading the switch inputs. A procedure for checking the switches is here: https://www.benzworld.org/threads/soft-top-gets-stuck-going-down.2665913/#post14684122

I would not be inclined to replace any transistors at the moment.
Hello Mr. BobTerry99,

I measured voltage with both round connectors connected to instrument cluster and surprisingly I got on Y35 0,09V on Y9 the same 0,05V. I unplugged both round connectors and got 7,05V on Y35 again, so there is not error in measuring. The readings are very different from what you had. Does that mean anything to you?

I made some progress in other front. I soldered new ZTX 751 and roof part of RST module got responsive. The roof is not operational yet, but it is big step forward. So this is what RST module is giving me now. There is no alarm (sound) any more, RB switch lit shortly up when I turned ignition on, as it should be and roof power switch (S84) now is constantly lit up when ignition is turned on (engine not running). When roof power switch is pushed back, then both windows start to go down and when they are down then process stops, I could get windows up with the same roof power switch, I did the small cycle couple of times, tried to hold switch for 10 seconds or more in down and up position and then only passenger windows was rising or lowering with roof power switch. Driver side window froze in upper position and it does not move even with regular window power switch, I can hear relay clicking in RST though, when switch is pushed up or down.

Roll bar was and still is in up position and I can't get it down. Roll bar is not lowering when RB switch is pushed and I can't hear any of relays clicking in RST module. Tried to hold RB switch up for 10 seconds and then lowering RB, but nothing. I know that I will not be able to operate roof until RB is down.

I had many error codes in RB module 3, 5, 6, 7, 8. I finally I was able to read codes from RST module I got only one 23, which is RB module, tried to erase it for 3 times, but nothing. Then erased RB module errors, could clear all but 4, 5 and 8. 4 and 5 I guess are ok, because both seats has been taken out and all wires disconnected, but for error 8 I'm not sure. After that error 23 on RST module cleared. But still could not lower RB and roof is not operational, just one window moves now with roof power switch.

My apologizes for such a long message, but I wanted to put out all details for anyone who will have similar issues in the future.

I'm new to the forum, so I don't know should I continue this tread or add messages to some of the existing threads, since I'm not sure has the issues with RST module has been resolved or not.

The goal of course is to get RB and roof operational. Any ideas what should be the next steps?
 

·
Outstanding Contributor
'03 SL500, '03 SL55, '97 SL320, (2) '91 300SL, (2) '91 500SL, '00 S500 -- all for sale
Joined
·
4,173 Posts
I measured voltage with both round connectors connected to instrument cluster and surprisingly I got on Y35 0,09V on Y9 the same 0,05V.
This is different from my car, but it may be of no consequence.

The light in the roof control switch is illuminated continuously because the top is not recognized by the controller as being secure. I'd solve that issue as explained in post #11.
 

·
Registered
Joined
·
57 Posts
Discussion Starter #14
This is different from my car, but it may be of no consequence.

The light in the roof control switch is illuminated continuously because the top is not recognized by the controller as being secure. I'd solve that issue as explained in post #11.
You are right! It turns out that roof front limit switches were not closed. I fixed this issue and now roof power switch S84 in not constantly lit. With this fix I got RB operational with switch as well. With s84 switch both windows roll up or down, but roof is still not operational and now I have new error from RST module, error 6 Limit switch, left locked, soft top fabric bow.

Roof is manually up and closed. I disconnected Y connector to RST module and checked switches by measuring Y pin input to ground, so 16, 17, 18, 19, 20, 21, 23, 24, 25, 26, 28, 31 were closed and 27, 30 open.
 

·
Registered
Joined
·
57 Posts
Discussion Starter #15
I manually lowered soft top and with soft top down I have such errors 6,7,20, 23. As for 20 if it somehow connected to Y57/1, then during process of lowering roof, pins got disconnected from Y57/1, there is no normal connector, just the pins connected. I will fix that of course.

Limit switch, left locked, soft top fabric bow and Limit switch, right locked, soft top fabric bow are the most rear accessible from trunk? In order to test and fix them, should they be removed from car?
 

·
Registered
Joined
·
57 Posts
Discussion Starter #16
I read full thread you referred me on post # 11 and then some other. I don't have "X11/12" connector located behind the passenger-side footrest. Could it be the 90' 500SL didn't have it? Today I cleared RST module codes, then manually lowered, locked and then rised, locked soft top, taking new error reading from 11/4 and measured short to ground on Y connecter pins.

Soft top up I have such readings short to ground: 16,17,18,19,20,21,23,24,25,26,27,28 and open-circuit: 10,22,29,30,31.

Soft top down I have such readings short to ground: 20,21,25,28,29 and open-circuit: 10,16,17,18,19,22,23,24,26,27,30,31.

On RST only errors which came back are 20, 23.
 

·
Outstanding Contributor
'03 SL500, '03 SL55, '97 SL320, (2) '91 300SL, (2) '91 500SL, '00 S500 -- all for sale
Joined
·
4,173 Posts
I don't have "X11/12" connector located behind the passenger-side footrest.
I believe you should have it, but since you are adept at measuring at the connector it doesn't matter.

On RST only errors which came back are 20, 23.
The top will not operate with fault 23 present. If you can not clear it, then you will have to get a replacement roll bar controller or bypass it's status signal to the roof controller.

Code 20 indicates the roof controller detects the hard top is installed. This is occurring because input 28 (top closed switch) is open when it should be closed. This switch is located by the left side mount for the soft top.

Another issue is input 31 for the roll bar lowered. It should be closed.
 

·
Registered
Joined
·
57 Posts
Discussion Starter #18
I believe you should have it, but since you are adept at measuring at the connector it doesn't matter.

The top will not operate with fault 23 present. If you can not clear it, then you will have to get a replacement roll bar controller or bypass it's status signal to the roof controller.

Code 20 indicates the roof controller detects the hard top is installed. This is occurring because input 28 (top closed switch) is open when it should be closed. This switch is located by the left side mount for the soft top.

Another issue is input 31 for the roll bar lowered. It should be closed.
I tried so many things, but at the moment I can't erase error 23 in RST. How can I bypass it's status signal to the roof controller? It is not for usage, but just for diagnostic purpose!
 

·
Registered
2000 SL500
Joined
·
277 Posts
I tried so many things, but at the moment I can't erase error 23 in RST. How can I bypass it's status signal to the roof controller? It is not for usage, but just for diagnostic purpose!
Can't help with error 23 but I did look at your limit switches measurements, see the attached PDF. Take a looks and see what you think. I think the differences I've pointed out are correct but I always want to hear what Bob has to say.
 

Attachments

·
Outstanding Contributor
'03 SL500, '03 SL55, '97 SL320, (2) '91 300SL, (2) '91 500SL, '00 S500 -- all for sale
Joined
·
4,173 Posts
Input 28 is closed and in the correct state contrary to what I posted.

I agree with Swany that 27 should be open, and it is the cause of the hardtop being detected. This is the white, adjustable "plunger" switch withing the top storage compartment.

How can I bypass it's status signal to the roof controller?
At the roll bar connector you can see a green/red and a green/pink wire. The other end of those wires go to the roof controller to report status. If you cut those wires and connect them with the red/blue wire (12 volts DC), then I think the roll bar controller is bypassed and code 23 can be cleared.
 
1 - 20 of 103 Posts
Top