The last time my alternator (regulator) went south on my 300E, the battery was venting sulphuric acid gas (you could smell and see the cloud emanating from the hood!!!). Voltage readings were 17+ volts as you have confirmed with yours.

Time for a new regulator as others have posted...

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car

Thanks everyone for all the help. I am going to bite the bullet and get one from the dealership for $96.00.

*************** has voltage regulator for like $25 USD, not sure about shipping to Canada. Check it out.

If you are in Vancouver, check out BMV in Richmond. They specialize in Mercedes and BMW, at a fraction of dealer prices. They call themselves wholesale, but that just means that their focus is on supplying the non-dealer Mercedes specialists. They will sell to you. I can't remember exactly the cost of a regulator, but I think it was $30 or $35.

If not, any alternator and starter rebuilder (the one in Kamloops, for example) has Bosch or Hella stuff at reasonable prices. Both Bosch and Hella make a regulator for your alternator (same one as on my '89 190e, I believe). No difference in quality from the dealer item, except that you don't get the blue box with the Mercedes logo.

The small private parts suppliers can supply most consumable stuff at decent prices. It makes running a Mercedes very economical. Even stuff in a Mercedes box is sometimes cheaper than dealer price. The dealer markup is huge.

I changed my voltage regulator yesturday and I took the car for a drive today and the car runs great. I tested the voltage while driving and the voltage is between 13.62 - 13.91

Thanks to everyone who helped with my problem.

Fab