|
Just a few mA over spec' will draw off enough to get you a denied start condition.
Anything under 10.5vdc whilst cranking will render all the convenience features into default....like windows express down etc. On some this condition also sets a Low Batt+ code.
In many towed here after battery depletion, many codes need cleared and features reset. Low battery condition causes multiple electronic upsets.
To check for draw you really need a Low Amp Probe that clips around a wire and capable of ranging down to 10mA .
Normal draw should be close to 20mA and drop to this after 90 seconds to 2 minutes as all the modules go to sleep...any draw over 50mA is considered a problem.
My rating of module 'failures to go to sleep' in my experience is as follows :
Seat Controllers left and right.
Rear SAM.
Convenience or Comfort Module.
Front SAM.
Battery Condition Monitor...found under truck latch usually.
Instrument Cluster. ..condensation damage in the multi-plug area.
Alternator ..both low charge rate and/or feed back to ground.
Heat and Air Controller.
Amp for entertainment system.
This list is a compilation of items I have replaced over the years on many different MB chassis.
If you sit in and close the door, the LED cluster mileage readout should go blank in a couple of minutes. If not, something on the CAN is staying awake.
If cluster blanks then check battery load condition for internal leak and level of charge with motor running. You could also leave battery unhooked for 24 hours and monitor battery voltage.
Pulling fuses will not isolate the fault, and most times cause more problems. Don't check for draw like this.
Personal choice ? On any CAN equipped MBZ vehicle is a OE Mercedes battery, especially those with dual battery.
regards
dk
.
|