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Discussion Starter #1 (Edited)
How to find a parasitic drain
You might ask... what's killing my battery?
Using this proceedure should get you started in the right direction.

Disconnect the positive battery cable and put a test light between it and the positive post. IF you have a drain, the light will light.
Now start pulling fuses until the light goes out. TAKE A PICTURE OF YOUR FUSE BOX FIRST! you will want to put the fuses back in their correct positions (different colors are different amperages)
Then start putting fuses back in. If the light comes on, keep that fuse out and continue installing the rest of the fuses.
AT this point you may have one or more fuses out of the box, you will need a wiring diagram to see what components are on those fuses. Then you can start disconencting the components to take them out of the circuit, and then other connectors in the circuit, until you can narrow down where the short is. Be aware that there are some circuits that will be hot all the time, and create a little draw, such as the clock radio, and keep alive memory for the PCM, perhaps others.
Note: Using this method justaguy found a stuck relay. He said, "So I used your advice and used the test light. I went though all of the fuses and the relays again. I climbed up and took the wires off of the glow plug relay and then the air heater relay, thats when the light dimmed. I replaced the relay... so far so good!"

Here is a great tip from our friend BogHog
When you disconnect the battery you may break a parasitic connection. How I do it is connect one lead of the test light or meter to the cable being removed and the other end of the test light or meter to the center of the post of the battery.Then I slide the cable off the post and I never interrupt the connection.You will find far more draws this way when you don't break the circuit.
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Make your own short tester/locator

Tech Make your own short tester/locator
 
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I Have one fuse that keeps blowing on 1997 ford expedition it goes to my tail lights license plate lights and cluster lights how do i find short
 

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Discussion Starter #5
Follow the link in post number one of this thread
 

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Discussion Starter #6
I had a drain in my Bronco. I mentioned it to my mechanic, who said "check the alternator." He was right. I disconnected it and the drain dropped significantly.
They have diodes, (I think three) and sometimes they go bad.
 

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i drive a 76 ford granada yesterday i drove to work car started fine, during my lunch it was dead, i jumped it and car started fine. i then left from work jumped it agan it started fine i got about a mile from home as i was sitting at a red light the light turned green before i could even give it gas my car was dead. i tested the alternator it tested good. so my question is whats is wrong with my car?
 

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Hi! I have a 1966 Fairlane 500XL, with a 289.

Everything was running great, then the battery died. So-

1) Replaced the battery
2) Replaced the solenoid

Got the car running, drove for a few miles, shut the motor off, filled the tank, started back up no problem, drove home, parked it in the garage, and 2 days later, the same gremlins came back.

1) All internal lights are working when I open the door.
2) Turn to key to "start", and everything dies. No internal lights, no starter turnover, nothing. Everything goes black.
3) Jump start the car, using my other car battery. OK start.
4) Drive around, park it overnight, go out to start it, and same cycle starts over, from step 1.
5) I just went out to try it a week later- same thing, except this time, the starter grinds, and the internal lights are dim when I back out of start, to "On".

I'm thinking grounding/ voltage regulator/ starter problems- ? Can someone please help me with some fault isolation? Thanks!
 

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Taking the steps in post one will find out if something is on when it should be off.

Then post your results.

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Maybe I'm missing something... but if you connect the test light to the post and the cable, aren't you still helping to complete the circuit...so of course the light would come on..?

I'm thinking the alternator on my F150 is bad, was installed a few years ago before I bought the truck (reman, I bet). Was driving truck and coming home the battery light was on. Now the battery is dead since it's been sitting.
 

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Maybe I'm missing something... but if you connect the test light to the post and the cable, aren't you still helping to complete the circuit...so of course the light would come on..?
This is correct. However with the ignition key removed, in theory, there is NO circuit operating. By design, this is absolutely true for vehicles pre-electronics. Removing either battery cable (just one) and connecting a test light in series with the cable end and battery terminal the test light should NOT come on. (Pos batt terminal and Pos batt cable end)

In the world of electronics with the key off there is current flowing. However that amount of current is so small that the vehicle should be able to sit for at least a week and the battery is not drained.

The typical spec for parasitic drain is 30 mA. (Miliamps or .030 amps) Most vehicles with electronic engine controls will have less than 10. And know that when the vehicle is shut down there are some electronics that are going through a shut down procedure. That may take a few minutes to accomplish. So a measurement for drain should be done after 30 to 60 minutes to get an accurate reading. That is why the fist post shows an awkward way of connecting the test light. Totally disconnecting the positive battery terminal and then reconnecting with a test light creates a turn on cycle for some items. This cycle takes some minutes to complete and draws more current than an at rest state.

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Had a drain. Found out that the positive on the back of alternator over time and vibration caused the wire to rub and expose wire which was touching post. Repaired it and paracidic drain is fixed . Good luck y’all
 
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