I was told by mechanic that I should
never jump start my 190E (1988 model) when
the battery is flat.
According to him, this could demage the
computer system. Any comment ?
Thanks

Whenever you jump start any car, the cables should be connected positive cable first, then wait at least 30 seconds. Waiting for a short period of time will allow the car with the weak battery to adjust to the newfound power. Mercedes was smart enough to realize that even their batteries can go dead & installed a voltage control device called overvoltage relay to protect the computers!!

If you do mess up you will usually blow the 10Amp fuse in the Overvoltage protection relay. It is the standard Red Blade Type fuse. It is located behind the black plastic cover behind the battery.

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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
LEAD TECHNICIAN FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

Hey Guys,
I know this is slightly off topic but what is the protocol or procedure for jumping a W124 V8? If a 400 or 500E needed a jump is there anything special to consider when dealing with the trunk mounted battery? What about using the 400 or 500E to jump another vehicle?

Just curious...Lee

Thanks guys, My car was jump started and
it caused the overvoltage relay to demage. That's why the ABS warning lights was on and the engine was running above 1000 RPM. Both
problem disappear once the relay got
replaced. Just wonder what others component will fail if the overvoltage relay demage ?

Thanks you.

LEE,
Always use caution when Jump starting any car, a few extra seconds spent making sure on good & proper connections always save in the long run! Also remember that the trunk has carpet, so extra caution isn't a bad idea.
When replacing any trunk mounted battery make sure that the replacement is vented under the car.