# quick electrical question about diodes?



## stephenscity (Oct 26, 2011)

I have completed the rewiring of my super c and all is working great however I seem to be having a drain on the battery when it sets.The battery is old but still takes charge. If I disconnect it while setting it seems to hold O.K. The alternator is a delco single wire. Have checked everything and have no shorts and the starter was just rebuilt. I thought about a kill switch or diode but if I go diode am not sure what type or how it would work. There is nothing on the electical except ignition. nolights or accessories. Any Ideas?


----------



## cyrush (Apr 20, 2010)

Silly Question??

If you disconnect the alternator, do y ou still have a drain ?? If so it could be a faulty rectifier diode in the alternator, Alternator generates A Cvoltage in a 3 phase configuration and the diode rectifier converts this to DC 12 -14 volts. whilst the diodes can be considered as a one way valve to electrical flow, they can occasionally fail open circuit which will drain a battery as you are experiencing.


----------



## Mickey (Aug 14, 2010)

Slight disagreement. An open diode doesn't pass current in either direction. A diode that fails shorted can pass current in both directions. Being a little loose in saying shorted as it could be a med-low resistance but not totally shorted.

Can test as cyrush suggested but also put a multimeter across the output terminal to ground and check for resistance. Should be fairly low in one direction and high (multiple k ohms in the other direction.


----------



## Miaugi (May 29, 2011)

I had a similar problem with my IH 484 and decided the easiest way to solve it was to install a battery cut-off switch. This totally isolates the battery when not in use and serves (somewhat) as a theft deterrent as an added bonus. If you are interested I think I have another cut-off switch lying around that I could sell at a reasonable cost.


----------

