I am new to this group and I apologize if I ask something that has been answered before.
My 2001 C320, out of warranty now, needed a new battery and I thought I would save some $ and replace it myself (stupid me).
However, after replacing it, the following items are no longer operational:
1. Wipers
2. Hazards/ Turn Signals
3. Rear sunshade
4. Trunk won't open from inside switch
5. Key remotes won't unlock trunk
6. Key remotes won't unlock doors, unless key is 1 foot or less from door
handle (I checked the batteries and both remotes)
7. Alarm
8. Fuel gauge shows 0 fuel all the time
9. The message display on the dash says 'Faulty Display'.

The wipers were acting funny a day before, when I had them on intermittent.
I was also getting strange error codes on the day the battery was low.

I checked all the fuses and none are blown.

I scanned the boards and found that this is more likely because a few relays have failed. Please let me know if you think this is the case.

If it is, could someone offer some help on how to identify the defective relay?
I see those 'cubes' on the fuse boards, are those the relays? How can I find out which ones correspond to the functions I described above? Lastly, where can I buy relays? (fastlane has none for my car)

I may sound like a novice when asking these questions, but this is not the case. I have performed major mechanical repairs on my cars, just not electrical. Yet, I have fixed electrical components for TVs and applicances. Bottom line, feel free to give advise that is complex to follow. Its not that I can't do it, but I won't touch this car's electronics without getting some advise first.


Thank you in advance!

I hate to ask this but I have known it to happen, could you have hooked the battery up backwards? Sounds a lot like reverse polarity. Just a thought.

I thought it was obvious that I did, otherwise my complaint list would include 'car won't start', 'smell of blown electonics', etc.

In other words, the car is perfectly drive-able, all other electric/electronics work, including headlights, radio, A/C, ESP, locks, etc.

The problem must be isolated to one or more relays, I think, I just need someone to confirm.

Thanks

It may be prudent to attempt some furthur diagnostics. As in, replace the fuse that powers the fuse with a known good fuse.

Failing that, what power is going to the display proper? Should be a fused line terminating at the connectors feeding power to the display. If you have 12volts there, could just be a coincidence that the displayed failed at the same time as the battery (low voltage will cause a higher current in electronic equipment).

Ron

__________________
1995 E320 -171k-km
1995 S420 -333k-km

did you ever figure out what was wrong? my car has the same issue and I really would like to repair without visiting my dealer.

sounds like you need a new rear sam, don't know why it just happens sometimes(so I have heard)

What is a SAM? New cars have way too many fancy and expensive electrical parts.

basically a fuse box

I just passed on a car with the exact situation yesterday. I also assumed it was the rear sam; however, I was not ready to start shotgunning on my customers dime. It has been driving me nuts on the actual cause of the failures.