DaveT.D.

I have received the "Battery not being charged" error message on my 2017 GLS 550 display twice in the last couple of weeks, never before. (Picture of a battery with + & - and the message "See Operator's Manual"). The error message goes away when I restart the car.

I am seeing the following from the vehicle data menu:

Engine off: UB: 11.9 V and IB: -16.6A.

Engine off

Engine on: UB: Climbs to 14.6 - 14.7 V and holds steady, IB: 20 amps initially, dropping to below 7 amps within a minute of engine starting even though headlamps on, rear defroster on. Very little if any variation when I bring the revs up from idle to 2,000. .

Immediately after start

Steady state (1 minute + after start)

(Sorry for the large pictures - need to figure out how to shrink them...)

Does not appear to be a weak battery as the car cranks quickly, and starts immediately, even in cold weather (33 degrees F here tonight). The battery is the original, 6 year old battery.

What are other people seeing for amps out of the alternator on the vehicle data menu after they start their GLS?

Is my alternator dying?

I'd appreciate any suggestions as to what I should do to diagnose further or other helpful responses.

Thanks,

Dave

DaveT.D.

How to access the Vehicle Data menu, if you don't know already:
1. Sitting in drivers seat with key, doors closed.
2. Foot OFF brake pedal
3. Center display shows total vehicle mileage and trip odometer
4. Press start button (or insert key and rotate to first position). Car should not start because your foot is NOT on the brake pedal.
5. Press and hold phone button on right hand side of steering wheel
6. Within 1 second of 4. above, press and hold the OK button on the left hand side of the steering wheel
7. Hold both buttons until menu comes up on center display, then release both buttons.
8. Click OK on left side of steering wheel to select "Vehicle Data"
9, Screen will now show battery voltage (UB) and current (IB). Negative current is discharging, positive is charging.
At this point you can start the car by pressing the start button (or rotating the key to the second, start position). The screen will continue to display voltage and current.

John CC

OP's indications look pretty normal. Your "steady state" shows normal voltage and 6.8 (?) amps charging current. The first voltage reading is a little low. I'd have the battery tested and, maybe replaced.