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Old 03-05-2018, 10:42 PM
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Default Alternator - bad diodes? 2004 Odyssey

Having removed the large black alternator output wire from the main under hood fuse block I turned the key to ignition on but not started, Between the output wire and its connection on the fuse block my meeter reads 10.98 VDC on the 20 VDC scale and 3.29 Amps on the DC Amps 10 amp scale. Do these readings indicate bad diodes in the alternator?

The Alternator does produce 14.38 Volts DC at 750 RPM and 14.42 Volts at 1500 to 3500 RPM after the car is first started and is warming up.

The problem is that the car's battery drains rapidly (in about 2 minutes) when the ignition switch is on but the key is not yet turned to activate the starter.

There is no significant Key Off parasitic current loss as key off current load is only 0.14 DC Amps. (0.10 to 0.50 being the acceptable range)

When the ignition switch is on but not yet started the most significant DC Voltage Drop circuits are:
4.7 V - ECU (PCM), Cruise Control
4.2 V - Back Up Lights, Instrument Panel Lights
5.5 V - Clock, Back Up

I have ordered a battery, starting and charging system tester but it has not arrived yet.

Last edited by Wylin; 03-05-2018 at 10:44 PM. Reason: clairity
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alternator, diodes, key on battery drain, odyssey2004

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