It could very well be a bad voltage regulator. The gen light will be full bright with the key on,motor off. As in no alternator output,compared to battery. The dim light could indicate a problem in the volt reg. Many parts stores have alternator rebuild kits which include bearings brushes and a regulator. Compare the price of the kit to a rebuilt alternator and you will be paying yourself for your labor at a rate of about $,29 per decade and the rebuilt will have a warranty ,your personally installed kit won't! If you in fact are dealing with a bad diode the kit will NOT fix your problem! You CAN buy the diodes and replace them yourself your labor compensation is now about $.13 per century and you STILL don't have a warranty! If you pull the plug that goes into the alternator or the Batt lead on the alternator(one at a time) and your 1.8 mil draw goes away you have located the draw and maybe located your problem? I would think ANY draw on the Batt lead would be a problem but a small draw on the regulator might be normal,not sure about that. Good Luck!
Ron

 

Be aware that most of the rebuilts, even those w/ lifetime warranties, are junk, some from overseas (read Red China). I replace three "lifetime" alternators in six months. Finally bit the bullet and bought an AC/Delco new and it lasted at least 'til I sold the car which was several years.

 

Unhook the positive cable and then hook a DVOM between the cable and the positive battery post to read the current draw with the engine off.

 

Thanks guys for all the information. I have the problem fixed now thanks to the info I recieved on the forum. It turned out to be the bridge rectifier in the alternator. I replaced the alternator instead of rebuilding it and the Gen light now goes off as it should. You guys on the forum are awesome. I am sure I will be back with another situation soon. Good luck to all and have a merry christmas.

Hop

 

Great! That was kind of a tough one! Apparently one or more of the diodes was shorted,usually bad diodes are open.
Ron

 

This was an interesting topic. I always wondered why the car was equiped w/ a light and a gauge, and had no idea that the two interacted. It's a topic to copy and put in the reference folder f/ sure. Thanks.

 

Usually, it's just the alternator rectifier bridge diodes that go out and I just pull the rectifier out and use an ohm meter to check the diodes if the car's voltmeter indicates the voltage under 13V.

Connecting the ohm meter leads in one way will be show an open circuit and the opposite connection should be a short.
If both connections are open or short, the diode is bad and calls for a replacement of the rectifier bridge. It takes only one bad diode to cause the voltage drop.
Replacing the rectifier bridge is a lot cheaper than replacing the entire alternator.

Usually the battery red light will be very dim when idling and with A/C and/or headlights on, but the light goes out when RPM is above idle speed which is when the alternator starts charging the battery.

When car sits with the ignition off, there is a slight power bleed from the ECM.
If car sits in storage longer than a week, disconnect the battery.

 

Vette82,
thanks for the info. As a matter of fact I have the car in the garage right now with the interior out of it. I unhooked the battery last night.