12 ' Mercedes-Benz Gl350
Long time listener first time caller. Had this 12' GL350 come in on a flatbed last week for no start, started with a boost. Charged battery over night, tested with impedance tester and carbon pile battery testing good. Aux battery is showing good on scan tool. Tested for parasitic draw well below the 80 mA. Alternator is charging on a test drive with scan tool attached. We had it here for a few days being driven in and out of the shop for a few other odds and ends (service and some rear air bags) no issues when starting, this evening customer comes to pick up slow crank then nothing battery dead again. I have been reading about SAM modules acting up but you would think that a parasitic draw test would show a draw. Bit of a head scratchaaa, any insight would be appreciated.
we have seen batteries test good after a charge, then do the same thing - test it again. Then test it again. and do not use a carbon pile tester -
If you have a factory level tool, there are logs saved with the last battery cycles. They also will log which module was keeping the Bus awake if that was the case. What tool are you using?
Using a Autel maxisys elite, so probably won't be able to see logs..
Customer had the battery replaced recently? Is the battery fitted adapted to the car if the adaption is available?
Then with your draw being okay on shut down the battery is fo-barred!
Load test battery and verify age. Any battery older then 4-5 years is on borrowd time in a Euro. However I would put a meter on it and record amperage draw overnight to verify CAN is not waking up at times.
Is this a Keyless Go vehicle? We have a car here right now that was going to be towed in because of a "no start" condition. door locks would not respond to the remote too. Removed the push to start button and used the Key to turn the ignition, and fired right up. car sat over the weekend, and the battery was at 6+- V Connected a charger and the remote started working, along with the Start…