I know there are several threads in regards to convenience function shutdown, visit workshop message, but I have an unusual problem that maybe you guys could help me with,
Problem first reared its head 3 days ago when I turned the AC on max, visit workshop light, AC fan speed slowed, and convenience functions were disabled
Once I returned back to work I read a couple of threads and tested the following with these results
Key not in the ignition:
Main Battery 12.5Volts
Aux. Battery 12.67 Volts
Key in turned on to power glow plugs:
Main Battery 12.5
Aux. Battery 12.6
Car started and running message alarm on dash:
Main battery 14.5
Aux Battery 14.4
Check engine light and glow plug light are both on now,
Thinking this was unusual and may be software related I decided to take the car to the local mercedes dealer. I agreed to $105 diagnostic fee, 1 hour later the service writer called and said that i had several problems (check engine light, glow plug) and it would be $105 for each issue, I informed him that all the lights came on at the same time, he did not back down, so I asked him to find out why the convenience features were shutting down. Two hours later I get a call and they tell me both the alternator and aux battery are bad and need to be replaced TOTAL around $1400. So I told them I would be by to pick the car up and asked that they explain how they came to the conclusion that both of the items were defective. The mercedes program told them, volt meter on the battery? No - Load test the battery? No, Test the alternator? No Wow $105 and I am no closer to any resolution,
Is there a relay or an amplifier that may be defective between the battery and computer, Any help would be great?

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Camper
83 300D
87 300 SDL
96 E300

Considering the year of the vehicle, I wouldn't be surprised if one or both batteries were on their way out, meaning their output amperage is decreased. But I am just taking a stab in the dark. I would see if you could get the aux battery tested.... Do you know how much an aux battery costs to replace? May be worth just to replace it due to age.....

Any idea on the amp output of the alternator?

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#dieselFLEET
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'97 E300
'99 E300