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12.48v on battery causes gauge failures, CELs and needs to be replaced.
Just an FYI (And I know there is a Sticky on faults from removing battery, and STF did not yield my experience exactly...)
Read out went from a perfect 13.8/14.2v when running under load to CELs and dead gauges and 12.9/13.0v running. Literally overnight.
Battery was OEM from 2004, so I can not complain, it didn't even really slow down when cranking...
This is an FYI to other forum users.
The information below I was able to gather from various places, and compile here for you after my experience;
#1.) Battery should be around 12.5v before starting. It shouldn't drop below 11v during start and should be around 14v after start.
#2.) Battery should be close to 12.8v when not running. While under load it should be in the area of 14.4v running.
#3.) 100%=12.68v 50%=12.24v 25%=12.06v
#4.) After an overnight sit the battery should read with a multimeter close to 12.6v, 12.5 is boarder line and 12.4 is too low. Running you should see 13.8v+
You can test with your volt/multimeter, with the IP by key in second position showing mileage and pressing dimmer 3X, the Climatronic digital display by holding [REST] for 10 seconds and then go to line 24, or...use a plug in meter with you 12v outlet/cigarette lighter.
Last edited by BF_JC230; Aug 30, 2020 at 10:50 AM.
Hi,
The lower image shows that the fuel gauge responded - Looking at this again, out of context I can understand your excellent question.
This was taken after fuel up and re-start. In BOTH images I am at a dead stop.
My speedometer with this failed/bad battery would not respond, "bounce up" to the speed I was at, and then get stuck around 40MPH only to fall down and then "bounce up" again.
Here is is stuck (again car not moving with the engine running) at 30MPH.
Thanks for asking!
Again, just trying to share my experience (and first CELs) for others if they experience similar gauge cluster warning lights and dead/faulty gauges.
That is exactly why I am sharing...this freaked me out...
I only operated the vehicle one "full" day like this, as I needed it.
Upon seeing the battery was at ~12.5v I thought (that's okay...) my mind then raced from EIS (had no TPMS either under this condition) to SAMs to CANBUS to Voltage Regulator...I searched forums and the web that night.
(Closest thing I found was another w203 that had a bad sunroof switch sending corrupt CAN signals constantly and caused similar dash freak out...he changed the UCP and everything went back...)
EIS did not make the normal "nnvvvroom" sound after removing key - it happened a few seconds after..but all keys worked, handshake went through and key turned/engine cranked...
SAMs...I knew they all were operational, no light flickers, no other oddities and rear SAM ensured fuel gauge...
CANBUS, from what I could tell was okay by "feel" as everything else was fully functional - and FiberLoop was good - everything on the ring worked...
Voltage Regulator was doing it's job as it fluctuated with load...
Started simply and changed battery (especially knowing its age) and all is good. Local dealer scanned/cleared codes, (of which only LOW VOLTAGE was showing but I never received a warning...a message or any communication other than these lights and faulty gauges) "vehicle operating as designed" is what was reported after change.
Now the EIS goes "nnnvvrooom" upon removal of the key and everything is as it should be.
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