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240z which fuse box circuits should see 12v when key is off?


adivin

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My ignition switch will only go in the on and start position.  Of course this led to a new dead battery.  I was wondering which fuse box circuits should see power ONLY when they key is in the on position?

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That's a loaded question.

Let me phrase it another way. What circuits can only be powered when the ignition switch is on?

The fuses with red only are powered with the key in ON.

The fuses in green use the combo switch (headlight/parking light switch). The common fuse is for the cigarette lighter. The clock is on the same fuse as the dome lamp and map light. (I think the wiper park function is on that fuse, too.)

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So what could drain the battery?

  1. Bad voltage regulator
  2. Bad alternator
  3. Clock (even if it's not running)
  4. Dome light, map light, and glove box light (door not closed all of the way - Note: This only applies to the 240Z. The parking lights have to be on for the 260Z or 280Z glove box light to come on.)
  5. Aftermarket stereo
  6. Aftermarket alarm
  7. Aftermarket accessory like remote locks (The previous owner had that on my 260Z. I removed the remote lock and fixed the door lock properly.)
  8. Unknown cross-connection
  9. Short in the starting motor (unlikely but here for completeness)

To help you with the diagnosis

  1. When did it start?
  2. How long does it take to drain the battery?
  3. Do you know how to use a voltmeter and ammeter?
  4. Do you own a test light?
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Steve thank you for this info!  My ignition switch will not move in the off position.  Using a voltmeter, I verified that I am indeed getting power to all of the circuits you circled in green.  The car starts no problem.  I got it started for the first time in 16 years last week.  I didn't realize the situation with the ignition switch until today when my one week old battery was dead.

 

 

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Ok, for the circuits in green, does the key have to be in the ON position AND the combo switch on?  Will they power with the key in the off position and the combo switch on?

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I think I was misreading the ignition switch and it is functioning correctly.  I used a voltmeter to check the fuse circuits and everything is as you described EXCEPT the third fuse from the top on the right (Park, Tail) gets 14v all the time, even with the combo switch off.  Now what lol...

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Am I correct in assuming my battery drain is due to that circuit seeing power all the time?  I don't suppose the problem could be in the combo switch since the other two circuits are unaffected?  

Looking at your list:

I don't have a voltage regulator.  It is internal to my new alternator.

I don't have a stereo or radio.

I don't have any aftermarket accessories. 

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22 minutes ago, adivin said:

Am I correct in assuming my battery drain is due to that circuit seeing power all the time?  I don't suppose the problem could be in the combo switch since the other two circuits are unaffected?  

Looking at your list:

I don't have a voltage regulator.  It is internal to my new alternator.

I don't have a stereo or radio.

I don't have any aftermarket accessories. 

No. If there isn't a load, such as a light on, a hot fuse won't cause a drain.

An internal voltage regulator is still a voltage regulator. A failure of that component could cause a battery drain.

1 hour ago, adivin said:

Ok, for the circuits in green, does the key have to be in the ON position AND the combo switch on?  Will they power with the key in the off position and the combo switch on?

For some reason I missed your question. ONLY the circuits in red require the key to be in the ON position to be energized. You can turn on the headlights and parking lights with the key any position.

So, going back to my original questions, do you know how to use an ammeter? If not, do you have a test light? One or the other is likely to be necessary to find a cause for draining the battery.

Have you checked all of the other items I listed for potential drains? Again, how long does it take the battery to drain? 

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2 hours ago, SteveJ said:

No. If there isn't a load, such as a light on, a hot fuse won't cause a drain.

An internal voltage regulator is still a voltage regulator. A failure of that component could cause a battery drain.

For some reason I missed your question. ONLY the circuits in red require the key to be in the ON position to be energized. You can turn on the headlights and parking lights with the key any position.

So, going back to my original questions, do you know how to use an ammeter? If not, do you have a test light? One or the other is likely to be necessary to find a cause for draining the battery.

Have you checked all of the other items I listed for potential drains? Again, how long does it take the battery to drain? 

I can say how long exactly it took for the battery to drain.  I do know it drained over the course of a week. 

I do understand the basic concept of how to use an ammeter, voltmeter, test light etc and I do have a multimeter, although I don't have much experience.  

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Is the horn relay still connected? If the wiring is stock, the only way for there to be a complete circuit is for the green/black wire in the steering column to be connected to ground. When you press the horn button, the button connects the tab on the horn wire to the steering column. You may want to take the cover off the steering column and make sure the combo switch wasn't installed too close to the steering wheel. Is it a stock or aftermarket steering wheel?

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Mystery is solved.  I thought for sure it was the horn relay, but it wasn't.  The problem was the connection for the horn in the steering wheel.  Many moons ago when the car was being prepped for an ITS track car, I put a Sparco steering wheel on and apparently left the horn connection just dangling inside.  Sure enough this was the cause of the drain.  Steve, thank you so much for your help.  You were a big help, especially when you kept asking me if I knew how to use an ammeter lol.  

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