I apologize for the long post, but I wanted to provide some background.....
I am the second owner of a very nice 2010 C350 with about 190,000 miles. I bought the vehicle about 9 months ago, and I didnt have any problems with it. I did update the audio system to include this and added some kicker 12" subs, and a backup camera about 6 months ago. So far it was a great car, I was really enjoying. The vehicle was high mileage vehicle but the original owner drove from north of San Antonio to south of San Antonio for work and racked up 175,000 before I bought it. They kept the car in great condition and I previously owned a C230 that I drove to almost 300K miles. Then a strange problem started when the weather started to turn cold my battery died and I started to notice some strange intermittent electrical issues. I jumped the car and drove it home and started to notice problems. The lights restarted almost on what seemed to a 2 minute cycle turning on and off, the turn signals stopped working completely when using the turn signal (yet the hazards still work), the radiator fan runs full speed all the time, the brake lights do not come on, and the windshield wipers dont work on demand, but randomly come on and turn off. I took the car into a shop and they tested battery and it needed to be replaced. The intermittent electrical problems stopped for about a week, I thought the issue was due to the low powered battery, but on another cold evening the problem came back and the car is usually in this state. I took the car back to the shop and they said I needed to take it into the dealership. I did that and they replaced the pre-fuse box for $852, basically no change in functionality and they wanted another $500 for 3 hours of work to search around for the root cause. I told the dealership no to searching around to find the problem since the cost was so high and they couldnt guarantee a fix. I expected them to have the tools to diagnose the problem. I picked the car up from the dealership and drove it home. Its been sitting in my garage ever since. I backed the car out of the garage over the weekend and parked it in the driveway and the headlights wouldnt shut off for most of the day and the battery died. I used my trickle charger to charge the battery up enough to start the car so I could move the car back in and when I did so everything was working again for about 5 mins. I took the car off the trickle charger and then all of a sudden the fan kicked in at full speed and the all the electrical issues returned. After googling lots of symptoms it seems that several people have had similar issues, but I havent seen anything posted about root cause. I am hoping some folks on this forum can help me troubleshoot. It seems like it should be a fuse or something, but the dealership says I have to replace the whole fuse box if a fuse is blown, I laughed when they told me that. The dealer is blaming the aftermarket audio equipment or someone that jumped the car backwards. Neither of which I think is the real problem. Also the MB Go system is not working anymore, the push button start/stop was the first indicator of a problem and the car wouldnt stop running unless I used the key.

 

I am going to suggest the ignition system is stuck on, thus draining the battery

that's a 100% guess

 

It was water damage. The windshield was leaking. The insurance totaled the vehicle, but I took a risk and bought it back. I was hoping drying it out and replacing some boards would fix the issue, but no luck so far. Does anyone have advice on next steps?

 

i am having the exact same symptoms as you on my 2009 c300! I’m wondering how you got your insurance to cover it?

 

how did you end up finding out it was water damage and the windshield leaking where? Because I have the same codes and same exact problems, also I can’t even read the obd2

 

[QUOTE=gmabrito;7641115]I apologize for the long post, but I wanted to provide some background.....
I am the second owner of a very nice 2010 C350 with about 190,000 miles. I bought the vehicle about 9 months ago, and I didnt have any problems with it. I did update the audio system to include this and added some kicker 12" subs, and a backup camera about 6 months ago. So far it was a great car, I was really enjoying. The vehicle was high mileage vehicle but the original owner drove from north of San Antonio to south of San Antonio for work and racked up 175,000 before I bought it. They kept the car in great condition and I previously owned a C230 that I drove to almost 300K miles. Then a strange problem started when the weather started to turn cold my battery died and I started to notice some strange intermittent electrical issues. I jumped the car and drove it home and started to notice problems. The lights restarted almost on what seemed to a 2 minute cycle turning on and off, the turn signals stopped working completely when using the turn signal (yet the hazards still work), the radiator fan runs full speed all the time, the brake lights do not come on, and the windshield wipers dont work on demand, but randomly come on and turn off. I took the car into a shop and they tested battery and it needed to be replaced. The intermittent electrical problems stopped for about a week, I thought the issue was due to the low powered battery, but on another cold evening the problem came back and the car is usually in this state. I took the car back to the shop and they said I needed to take it into the dealership. I did that and they replaced the pre-fuse box for $852, basically no change in functionality and they wanted another $500 for 3 hours of work to search around for the root cause. I told the dealership no to searching around to find the problem since the cost was so high and they couldnt guarantee a fix. I expected them to have the tools to diagnose the problem. I picked the car up from the dealership and drove it home. Its been sitting in my garage ever since. I backed the car out of the garage over the weekend and parked it in the driveway and the headlights wouldnt shut off for most of the day and the battery died. I used my trickle charger to charge the battery up enough to start the car so I could move the car back in and when I did so everything was working again for about 5 mins. I took the car off the trickle charger and then all of a sudden the fan kicked in at full speed and the all the electrical issues returned. After googling lots of symptoms it seems that several people have had similar issues, but I havent seen anything posted about root cause. I am hoping some folks on this forum can help me troubleshoot. It seems like it should be a fuse or something, but the dealership says I have to replace the whole fuse box if a fuse is blown, I laughed when they told me that. The dealer is blaming the aftermarket audio equipment or someone that jumped the car backwards. Neither of which I think is the real problem. Also the MB Go system is not working anymore, the push button start/stop was the first indicator of a problem and the car wouldnt stop running unless I used the key.

I’m also facing that issue. Have you been able to solve it?