I know they often spark inside.. just electricity in and around the brushes; but why would they spark outside the aramture? ANd is this dangerous with ehaust fumes in the engine bay?

Diesel fumes aren't particularly explosive, unlike gasoline fumes... but it's probably still something that shouldn't be happening.

One of the electricians will know why.

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http://www.appstate.edu/~salleyms

"What could possibly go wrong?"

~Michael S.~ -
1986 M-B 300SDL, retired due to rust and electrical problems. Donated engine to:
1987 M-B 300SDL, odo dead. New project.
1982 M-B 240D, odo stopped at 308,000
1982 M-B 300SD, 175,000
1989 Dodge Ramcharger, 87,000 - 4wd, 318

Check your brushes and armature. If the copper braid is contacting other things, you can see sparks in other places.

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

06 VW Jetta TDI 133K miles-replaced the other '06 that quit after 300k miles. (did not catch the bad cam in time)

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 195K

90 Dodge D250 5.9 Cummins/5 speed. 400K

There was a nut in the rear section bouncing around !!

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My SEC's alternator had the inner bearing cage of the rear bearing wandering around the rear of the alternator.

No undue noise from the bearings, and the only indication I had that something was wrong was when it turned on all the dash warning lights, as well as the fuel tank empty light for one minute, before going back to normal operation. Pulling the brush holder to check the brush condition, I found the bearing cage leaning against the commutator rings.

When I split the case to figure out what was going on, all the little balls fell out on the workbench!

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-Josh
Testing the cheap Mercedes axiom, one bolt at a time...