Roll Bar Control Module for '91 300 SL
 

Hi, I'm new to this forum. I found an older thread on the soft top and roll bar control modules for a 500 sl, and I have a similar question. I am trying to figure out how the roll bar control module works on a '91 300 sl. I was hoping someone might be able to post a wiring diagram and/or a list detailing what the inputs and outputs at each pin on the module are. As I understand it, this module takes input from switches located on the rear suspension and contains angle sensors and accelerometers internally and deploys the roll bar when the required sensor outputs are produced. What other inputs does the roll bar module receive and what other modules does it interact with? I believe it also locks the seat belt retractors when the angle sensor produces a certain output, is this correct? If so, how does it lock the retractors and does it lock them directly or through another control module?

Thanks. I would really appreciate any input/advice you could offer.

Chris Clarke

I also own a 91 300SL. Unfortunately, I don't have a schematic diagram of the roll bar controller. I've never had a problem with mine that couldn't be fixed by clearing out the error codes. There is much in the forum archives on how to do that. BobTerry may be able to help you if you seek help directly ( via PM ). What problem are you having with the roll bar?

tecqboy,

Thanks for the reply. I'm actually working with just the roll bar control module and I don't have the rest of the car. I am trying to set up a demonstration to show the retractor locking when the control module(angle sensor) is tipped past the threshold. In order to do this I need to provide all the inputs the control module normally receives.

Thanks,

Chris Clarke

roll bar deployment on a 91 300 sl
 

My roll bar deployed today on my 300 sl hit a bump and it deployed.
Now it won't deploy back down. What does it take to get it to go back down and how much should I pay to have someone fix this???

:o

This is a pretty simple DIY ( Do It Yourself ) fix if you are not intimidated by the process. You need to build a "tool" from a switch, and an LED with a resistor. There are detailed instructions previously posted on this forum and others with Radio Shack part numbers. You can use the forum search tool. ( Roll Bar ) Then......

Roll Bar Codes and Reset Procedure.

Locate the diagnostic connector: Under the plastic cover near the hood-up switch on the passenger side of vehicle near the strut mount.

Connect LED + to pin 16 (+12V) Connect LED – to ground ( Pin 1 ). Use an LED with resistor.

To read error code: Use a push button switch to short pin 7 to ground (Pin 1) hold 2 to 4 Seconds. Watch the LED flashes.

To Erase an error code: Close switch 6 to 8 seconds.

Code 1 = No faults in system.
Code 2 = Roll Bar Control Unit
Code 3 = Voltage Supply
Code 4 = Driver Seat Belt Lock Relay (K18/2) open or short circuit to terminal 30 and/or 31
Code 5 = Passenger Seat Belt Lock Relay (K18/3) open or short circuit to terminal 30 and/or 31
Code 6 = Roll Bar Deployment Solenoid (Y57/1) open or short circuit to terminal 30 and/or 31
Code 7 = Left and/or right rear axle switch open or short circuit to terminal 30 and/or 31
Code 8 = Roll Bar Warning Lamp
Code 9 = Roll Bar Warning Lamp and/or impulse counter held too long to erase malfunctions
Code 10 = SRS Control Unit

Some codes may required several read / clear cycles to totally clear.

I am having this problem, so I need to make the tools to diagnos.


LED with resistor ?????
Can you provide a little more detail, I am very handy, just want to make sure I get it right.


Thanks.

Buy 276-270 LED at Radio Shack. It has a built in resistor and operates directly from 12V. LED's are polarity sensitive, so be sure to watch the plus and minus leads when you build your tool.

+12v<________+LED-______________>|<_______ \_________>Ground

Pin 16 ------------------------------Pin 7-------switch----------Pin 1

( can't draw with a text editor )

LED 276-270 works. So does 276-209. The difference is one has hardware for mounting in a hole and the other does not. To facilitate connections I use banana plugs (picture).

You don't need the LED to read codes for the roll bar or soft top controller on a '90-'93 SL. After shorting the appropriate diagnostic socket watch the light in the top switch for soft top codes or the malfunction lamp in the instrument cluster for roll bar codes.

Thankyou very much.

Appreciate the info that the 90 reads out via the roll bar switch.

I have a feeling it's just any electrical gremlin, I had a short last year that really messed things up. Had to clear codes etc to get the soft top to work, a few months later this occurred. (I's a garage queen right now, so I don't drive it much, just too busy.

Gonna read the codes, then try clearing it.



Thanks again.

Well, it didn't work.

The light on the Rollbar switch just flashes like a heartbeat, and the dash lite is on solid.

Is there a special procedure with the key?
I seem to remember that to read the top codes I had to cycle the key a certain way along with shorting the pins.

I did check the fuses under the hood, would the roll bar have any in the trunk ??

Roll bar works fine manually, while I really like the looks with the bar up, the windscreen works really nice and it requires the roll bar to be down.


Thanks

Fuse #4 in the trunk is for the roll bar controller. I am unaware of any special key sequience. The codes do not flash via the roll bar switch lamp in my car ( 1991 300SL). I use the LED "tool". I believe bob terry is refering to a lamp in the VDO.

Thanks Tecqboy, I'll hit Radio Shack tomorrow or Monday.

I should have just checked the trunk fuses.

One note, if it helps, the lights in the roll bar switch STOP flashing when the bar is up, but the dash light stays on solid all the time.

Don't forget to check the roll over sensor switches on the rear axle.

OK, I'll play stupid here. It does comes naturally, but.


How can I test them, what should I look for ???

Are they repairable or do u just replace them ?


Note I used to be a dam good weekend mechanic, although long before all these fancy electronics (other than brakes and A/C, I fixed it, rebuilt it or installed it).

So I am asking to try and save some grief once I get under the car.


Thanks

Well, the reason the roll bar is there is to pop up in case the cars rolls over. This condition is detected by a pair of switches mounted on the rear axle. They are easy to spot if you look under there. The roll bar will pop in just a few tenths of a second if one of these switches is tripped; unlike when you use the console switch to raise or lower it slowly. If you've never experienced a roll bar emergency deployment, you will be quite surprised if it does happen ( like when going over a big bump or hitting a bad pothole.) Inspect the switches for freedom of movement and any obvious damage. If your trouble shooting leads to a suspected switch problem, you can check them with a continueity meter.