I've got a strange problem that I have been unable to diagnose for years now, but have been able to find workarounds until now.

The car is a 2000 CLK430 convertible, 130k miles.

The situation: When the starting the car, the normal sequence of events includes the dashboard lighting up and showing all the warning lights and making a couple different beeps and chimes. My CLK starts as normal and the dash lights up EXCEPT for the SRS light at the bottom right of the cluster. The car also does not make one of its chime/beep noises. When this happens the majority of the interior electronics do not work at all. This includes steering wheel buttons, windows, wipers, rear defroster, horn, power mirrors, heated seats and turn signals. The radio doesn't turn on as normal, but hitting the power button works and the stereo works 100%. The interior and exterior lights, hazard lights and HVAC work as normal . This happens irregularly and I have found no pattern or action that causes this. The car is perfectly drivable at this point as long as it's not raining. Within 15 minutes of starting the car, the SRS light eventually flashes on and back off, the chime happens and all electronics come to life. Sometimes turning the car off and back on or cycling the key from off to run without starting the car will get the chime to happen and SRS light to flash too.

More recently I stumbled upon a trick to force the SRS light to flash and chime to happen. Pulling the turn stalk for the high beam lights would somehow trigger the process right after starting the car, however this method is no longer working and the SRS light and chime never happen even on a drive as long as 30-45 minutes.

Writing this all out sparked my mind to think battery and/or alternator. A dying battery can cause all sorts of random issues but for it to only be this issue only and so consistently? I have not replaced the alternator and the battery was replaced when we bought the car 4 or 5 years ago.

Any thoughts?

 

Update:

Got 14.1v at the jump post in the engine bay with the car running and 12.0 - 12.1v at the battery with the car off. Will test again today after the car has been sitting 24 hours.

Whatever is happening, it's quickly getting worst. After a 45 minute drive yesterday, the SRS and Roof folding light were flickering/dimming in and out like it was trying to activate, but never did.

 

A battery is not expensive. As it is already several years old, I think it is a good time to change it and check its effects.

 

I came across another thread where someone was having a similar issue and they believed all the components that wouldn't work were tied to the front SAM. So I picked up a used one, confirmed the part number matched and am still having the same problems. I've also replaced the alternator, thinking the voltage regulator may be on it's way out. It was worn, but not to failure, so that was another failed attempt.



I don't know the systems of the car well enough to understand what all the non functioning parts have in common? Does anyone have any guidance?

 

Your battery voltage is very low. Should be 13.2 VDC. Low voltage is not kind to electronics.

 

I also have a 2000 CLK430 cabriolet and have the exact same issue. I found that disconnecting the battery (neg terminal) for just a few seconds fixes everything - but that a hassle. It has me baffled. I suspect one of the signal acquisition modules ("SAM") is going bad, probably corrosion from moisture