anc4

happy fathers day!
my wife's 2003 r230 w/ 70k miles, is having electrical issues. the coolant level and washer fluid level warning lights are constantly on. the red battery light is always on and the convenience offline is on for approximately 10 minutes then goes out. the interesting thing w/ the convenience offline light is that if i turn the car off after the light goes out and restart the car, it takes another 10 minutes for the convenience offline light to go out. anyone have this happen and/or recommendations? thank you

bobterry99

When the key is turned on the battery control module checks the voltage on the rear battery. If it is below c. 11.5 VDC (?), then the electrical "offline" mode is on. It will unconditionally exist this mode after a period of time which in your case seems to be 10 minutes. Since upon restart you consumers are still offline, then your battery is not charging either because it or the voltage regulator/alternator are faulty. To discern which is the case, measure the voltage at the rear battery with the engine idling.

The red light can indicate a faulty alternator or, according to M-B, a particular stored diagnostic trouble code.

Did you check the level of the washer and coolant reservoirs?

matk

Do you have a trickle charger on your Convenience Battery? I had a load of seemingly unrelated warnings when my convenience battery became very worn. When I fixed that I had a total of 54 stored fault codes and a permanently on battery warning light.

Now that the battery is back to normal and codes cleared down, not a single one has reoccurred and the red light has gone.

anc4

my ctek died 2 yrs ago and i didnt replace it until recently, but i've put a trickle charger on it for the last 2 months or so getting it back to charge. when i charge it, i still have the same symptoms, i have topped off the coolant and washer fluid. did you have to clear the codes w/ STAR? i have a std obd11 and it doesn't show any codes.

matk

Yes to that, I had to clear all the codes down, STAR would be good but I used a Foxwell. I’d bet money you have stored codes.

bobterry99

I'd check both switches. First verify that each is plugged in. Next measure the resistance across each switch. You should read 5 ohms or less.

You don't need a wiring diagram, but if interested you can download them here and locate drawing 54.21-U-2122KA to see the circuit with the level sensors.

anc4

what about the convenience battery situation? taking 10 minutes to be able to use those functions (ie top, heated seats etc) each time the car is started.
which foxwell model would work?

matk

I used a Foxwell NT510

If your Convenience battery is fully charged you shouldn't be getting the reduced function for 10 mins. If however its run down you will, and even if you run the car and it restores, the moment you switch off it might do it again. Mine did exactly the same until I got the Convenience battery restored. It took over a week on a low power trickle charger to get there.

anc4

the convenience battery is showing 12.6 after i turn off the car and its still taking 10 min for the convenience offline to go away, is this due to stored codes that need to be cleared?
the voltage at the convenience battery w/ the engine at idle is approx 14v.

Austinsec

You have a battery drain I have the same issue, it could be anything . I had many give advice to no avail.

bobterry99

No.

Just before the next time you start the engine, measure the voltage across the battery cables of the trunk battery. If it is below a threshold (refer to my 1st post), then your battery is suspect, or you have a current drain; if above, then your battery control module is suspect and should be checked with Star Diagnosis or similar.

Austinsec

I tested mine I have a 2 amp draw with car off.

anc4

i have a norco tender connected so the voltage is always around 12.6.
can a foxwell nt510 tell me the issues or do i have to use STAR?
thanks for you help

bobterry99

So, if this is the voltage on the rear battery cables when you insert the key with no battery tender connected, then it seems to me the battery control module is falsely reading a lower voltage and erroneously taking consumers offline. A NT610 could certainly communicate with the battery control module and report the voltage it reads.

anc4

my bad, the 12.60 is w/ the tender attached, w/o the voltage drops into the mid 11's

bobterry99

Obviously you have a bad battery.