Question about 1990 Mercedes-Benz 190
Where is it located in the engine and how difficult is it to change?
It should be either just above the air conditioning compressor, or on the opposite side. It will have two wires coming out - a red wire ( 12 volt plus) and a black ground wire. The a/c compressor has metal fittings and rubber hoses as well as a clutch. No need to touch the a/c compressor. I changed alternators on my 300D models and 300 SD. They are very much the same. You will need to loosen the adjustment slider and physically slide the alternator to loosen the belt. Remove the wires from the alternator - probably a plug at the rear. If the car has a single serpentine belt the problem is more complex because so many units run off the same belt, including the water pump, fan and a/c compressor. Restoring proper tension is critical. The alternator swings in a vertical arc on a long bolt on the bottom or side that runs from front to rear. Replacement is not difficult - hold the new unit in place while you insert and tighten the long bolt, then reposition the tension slider and tighten that bolt. The tension needs to be correct or else the belt will slip and squeal and your battery will not charge properly. You may need a crowbar the achieve the right tension while you tighten the tension slide. Instead of replacing the alternator altogether, why not just replace the brush on a round plate at the rear. Most alternator failures involve worn brushes. The rebuilders simply replace them and sell a "rebuilt" unit. Make sure you can get brushes and/or a brush assembly before you start.. Loosen the tension but do not remove the alternator. Remove the two small nuts that hold the brush assembly at the rear and slide it off. Replace with the new one. Be sure you retract the brushes so they will slip back over the armature, and align with the retaining screws. Tighten them. Re-tension the belt and you're home free. I have done this on the road when necessary. Easier and cheaper than changing the entire alternator.
Posted on Dec 20, 2008
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Posted on Jan 02, 2017
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