R230 strange electrical fault.....help needed

[Gbrowncls55]

My wife's R 230 350 SL has a strange intermittent ,but becoming more frequent, electrical fault.
When you start it sometimes the dash SRS light and the roll bar light don't go off followed very closely by the command unit cutting off the audio and saying system unavailable. Usually but not always after 5 mins of driving the light go off and the command starts playing and everything is normal. when the dash lights are on and the comand system is down there is a strange clicking noise from somewhere around the passenger side by the roll over bar.
I know all sorts of things can happen when the voltage drops to a critical level so we replaced the quite old service battery in the boot. All was well for about a week then it all started happening again.
At fist I thought the clicking might be to do with the roll over bar motor but i'm now inclined to think its a relay switching erratically. The roll over bar raises and lowers as normal manually with the switch.
Anybody had anything like this or is an electrical whizz and can point me in a right direction. Thanks

 

[Gbrowncls55]

Nobody ??

 

[Gbrowncls55]

So code has been read and says "no voltage or open circuit at terminal 15" Just in case anyones interested. Problem is its so intermittent that as soon as we start checking the voltage at different places it starts working again and so there's nothing to check. Seriously maddening. If it just went wrong and stayed wrong we could find it pretty quickly. We have eliminated the fuse board and the front SAM. next stop ignition switch ....when it does it again.

 

[grober]

With voltage supply problems I always recommend checking the main voltage supply return paths ----main battery earth strap / engine earth strap/ alternator return path [to engine usually] but with a terminal 15 fault it might be a ignition switch related .

 

[c63chris]

Mine is not happy if not used regularly. If left on a charger it’s fine but on it’s own after a week there are all sorts of random things that stop after a while driving. Yours sounds a bit more than that though.

 

[imkaz]

I'd say check the batteries, especially the auxillary one. My ABS light used to flash when starting the car after a few days sitting (low aux battery). I bought a brand new battery for aux and the light no longer flashes after the car sits for a few days. If you're batteries are more than 4-5 years old, I'd say replace them.

Also check for water leaks front the bonnet vent on the passenger side of the car, I had all kinds of intermittent electrical problems from the wiring looom under the driving seat being submerssed in water.

 

[Gbrowncls55]

As I said we have replaced the service battery in the boot, and the car is bone dry inside. Had it back for a few days and its been fine, but it will start up again in due course I expect. When it goes again we'll check the ignition switch.

 

[imkaz]

Have you checked the carpets under the passenger seat. For me it felt dry on the outside, but only after lifting up completely to see the foam did I notice the water. Hope that helps!

 

[AndrewOl]

Had same sort of weirdness. Was down to water in the footwell. No wet carpets as it was coming through via a chassis rail from the scuttle area.

 

[imkaz]

Gbrowncls55 I also have a MB scan tool that should pick up any faults recorded in the car, that might help pin point the source of the problem. Even if the problem is intermittent old faults will be stored in the memory to be read.

I'm based near the A13 flyover.