Regularly occurring electrical drain when running

[Zoro]

Since day 1 when I purchased my 84 there has been a cyclic electrical drain while running that occurs at regular intervals(usually a few minutes) and triggers the battery light to come on about half way. Alternator has been replaced several times as have the battery and cables, belts are good. Never used to bug me but I now have throttle body fuel injection and the system is quite sensitive to this.

Anybody have any idea what could be shorting out that would draw down power for a few seconds at a time at regular intervals? It's baffled me and my mechanics for 6 years.

[eaglefreek]

Try replacing the solenoid if you haven't already. I had a bad parasitic drain when parked that would drain the battery in less than 2 weeks. Since I have the 4.0L starter with the built in solenoid, I removed the factory solenoid and replaced it with a relay and can now leave the car sit for several weeks and it will still have enough power to start it. Maybe there is a bad wire somewhere in the charging system. While running, have someone sit in the car while you wiggle the wiring harness in different places and see if you can make the light come on. Intermittent electrical issues are the most frustrating to track down.

[mo.eagles]

You say this occurs at regular intervals . Like a relay or switch turning on and off ? Maybe like A/C cycling ? Not saying that's it just trying to get an idea .

[carnuck]

Or rear defogger shorted.

[mo.eagles]

What do the rest of the lights , gauges do ? Does the temp gauge operate properly when the alt light is on ?

[Zoro]

When this happens and the batt light is half illuminated the rest of the lights will dim(dash, headlights, stereo) heater slows, wipers slow or stall completely and engine RPM drops.

Coolant and fuel gauge stay where they are.

[carnuck]

If it's not a missing ground wire from the battery negative to the body (sometimes they break inside so I add extras) then the alt may be messing up. A bump on the alt with a rubber mallet will tell you if it's bad or brushes need replacing. If you have the stupid double belt system for the alt, the slack between them both can stop the alternator from turning!

[Zoro]

Thinking I'll check the 2 prong plug & wiring from the side of the alt. One is a sensing wire and the other gets an on signal from the ignition switch that travels thru a 10ohm resistance light.

From the factory on the sensing wire does the voltage travel into the interior of the car (from the alt) then back to the solenoid or does it go right there?

I'm going to try running a new sensing wire off my alt over to the solenoid to see if that helps.

If it's not a missing ground wire from the battery negative to the body (sometimes they break inside so I add extras) then the alt may be messing up. A bump on the alt with a rubber mallet will tell you if it's bad or brushes need replacing. If you have the stupid double belt system for the alt, the slack between them both can stop the alternator from turning!

Alt and belts are brand spanking new and tension-ed as tight as can be. Single alt belt driven from AC compressor on this car.

This is alt #3 on this car and 4th or 5th set of belts so I'm ruling those out.

[mo.eagles]

Check to be sure you have a good ground from the engine block and the chassis . I had to trouble shoot an '82 thunderbird that when you opened the door the starter motor would engage and crank the engine over because the ground connection was removed from the rear of the engine block . Electricity does crazy stuff . Do you have an electric fuel pump ?  The alt wire should go to solenoid unless some has changed /added stuff. The more I think about this the more I agree with eaglefreek . Try another solenoid .

[Zoro]

I'll try the solenoid.

Running an electric pump now that I have fuel injection.

[eaglefreek]

I was sitting in a pizza a place and I had a flashback of having a similar issue a few years ago. One of the wires going into the connector had a break in it and once and a while the alternator light would come on as you described.

[carnuck]

That was going to be my next question. If the white wire is getting power but the red doesn't have full power (it goes direct to battery) or the fusible link between the battery and alternator is corroded or one of the battery cables are corroded/loose then the Delco alt will self destruct..

Echlin number VRC148

[Zoro]

Picked up the plug today, not installed yet because it got dark.

It appears that somebody put the red wire directly to the charge post on the alternator, when I replace the plug it will run direct to the battery.

I still need to install a new engine to chassis ground wire.

Here is what I did do:

Replace starter solenoid and solenoid to starter cable(both battery cables are new along with the battery as of last few months)

Connected ground wire from back of alternator to the solenoid.

Fired it up, went for a drive and now for the first time ever the coolant gauge spikes all the way to the top of the gauge at random times.

Thank you for the help guys