alternators
 

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I have a 1973 Press. 337 that when descending from alt.{airspeed a little higher{} the front alternator out light comes on. However when I turn off the rear alt. the light for the front goes off. conclussion; even now when I am in level flight the front alt. out light comes on intermittenly, if I shut of the rear alt. the light for the fromt alt. goes out, or if I load up the elect. system, for example turn on all elect. including landing lights,then front and rear light stays off. this is a two regulator system, I checked the front alt. by trying to turn it using cooling fan, cant do it . any ideas, thanks ;
thanks for the clue on the gas gauge, there was corrosion in the plug at the wing root. this is an awesome information center.
Rod Donner

It sounds to me like your regulators need to be adjusted. S/N 1399 and on are different from the older models in that instead of one regulator running 2 alt. each alt. uses one regulator. Check the voltage output from each alt. separately. It should be 27.5 +/- .2 volts. with landing light on. If they are out of adjustment, one will kick the other offline.

This was a common problem with some of the C402's I used to work on.

Had the exact situation you describe some time ago. Usually in cruise an alt. (Front I believe) would drop off and stay off till voltage dropped some then would come back on and stay on for a good while till it repeated the process mabey on the next flite. Anyway its a 73 G model like yours and we finally adjusted the alt like was mentioned in the previous post and the problem hasnt come back. I wouldnt ignore this as I believe it caused an alt faliure for me.I believe that the alt is cycling under full power and that cant be good.