I replaced the engine on my 2005 CLK500 and now i have a coolant check level light on and as well as the battery visit workshop light. All the auxiliaries are original from the older engine. Coolant is full and sensor is good, same with windshield washer fluid and sensor, and temperature sensor. Fan and fan control module are good too. Any ideas on what could be causing these lights? Any help would be highly appreciated.

Check voltage - you need 12.6v at rest, no less than 11v during cranking, and 14v at idle. If you don't have this, start by diagnosing the battery and/or alternator.

Yes I have at least 12.7 when the car is off, 14.2+ when the car is running

Looks like no one has experienced this issue before?

So I figured out the coolant level issue, bad coolant tank, the magnet in the tank was missing. New tank and light is gone. Only problem now is the intermittent battery visit workshop light. Battery is at 14.2 volts when running and about 13.2 when the car is turned off so I really don't know what is causing it. It only comes on once in a while and if I turn the car off and on again it's gone. Any advise would be appreciated.
Thanks

How were you able to troubleshoot the coolant tank to know a magnet was missing? Did you just completely comb thru the entire cooling system and take every part off? Did you do it or a shop diagnosis caught it?