Electrical (Charging) Problems
 

I've got a 93 W350 that started giving me charging problems a few weeks ago. I checked the alternator first, and it puts out 16V. Next checked the crank sensor. It looks ok, including wiring. The gap was at .030" and I set it to the spec at .050". I figured it was probably the ECU, so I got a new one from the dealer. By then, my battery was toast too, so I put a new one in. I also cleaned all the contacts for the grid heater and the solenoids wwhere the connect to on the driver's side fender. My grid heater also does not appear to be working or cycling like it should. I'm still only getting about 12V charging into the battery and my gauge doesn't show the 16V like it used to. Also, my speedo and odometer quit working about the same time. Any help on what to check next? I'm about at the end of my chain with this thing! Thanks

Mike

If your alternator voltage is 16V but the battery shows 12V then you have an open circuit between the alternator and the battery. Normally the alternator is connected to the battery at all times. The diodes in the alternator keep the current from going backwards when the engine is off.

I don't know if there is a fuse link in the circuit but I would get a sharp point on my voltmeter plus lead and poke it through the insulation of the fat wire which goes from the alternator and follow it until the voltage goes away or down to 12V then you have the open place in the circuit.

BTW, the battery at full charge should read 12.6V. You need about 14 volts to charge well. The 16V is simply where the alt is running unloaded.

Edwin

not sure if his applies to your vehicle..but similar problem iv'e had on a bus....the alternator 'live' goes to the starter motor..the battery 'live' also to the starter....could be a built up of crud or loose connection there....i'd be tempted to check the + connections more than the earth connections on the chassis/fender...gotta be worth a look...hope this helps.....