Mystery electrical power drain.
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Freshman User
Joined: Sep 2002
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From: Philly Area, PA
Mystery electrical power drain.
I was away for the weekend, but my brother-in-law was using my truck. I think on Saturday he went to start it, but it wouldn't turn over, so he jumped it. It started up, he ran it a while to charge the battery, tried to start it again, it wouldn't start, and then wouldn't jump. So he went, took the battery to an Autozone or something, they tested it, it was bad, he replaced the battery. Fast forward to this morning. I go to start the truck... not even a click. Just dead. Took a multimeter, tested the voltage, 8V. Way too low. Didn't have time to let the PowerShot work its magic, so I took a different car to work.
So, how to go about testing the power drain, any hints? Pull the fuses and test for current? If so, which fuses on a '91 F150 should have a power draw when the key is off?
So, how to go about testing the power drain, any hints? Pull the fuses and test for current? If so, which fuses on a '91 F150 should have a power draw when the key is off?
Senior User
Joined: Oct 2005
Posts: 446
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From: Germany
The shade tree trick we used to use was disconnect the negative battery cable and touch (clamp) your multimeter leads between the negative battery terminal and the clamp on the negative battery cable. If you've got a drain, this will show you how much of a drain you have. Pull fuzes one at a time to isolate it. Don't overlook the starter itself and/or the solenoid.
Hope that helps.
Dave
Hope that helps.
Dave
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Freshman User
Joined: Sep 2002
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From: Philly Area, PA
Ok, went through that process last night, wasn't any of the fuses, but when I pulled the connection off the top of the alternator the current dropped to zero. So I left that off, charged the battery overnight. Went out this morning, reconnected it, tried to start up, nothing. No clicking, nothing.
Starter, solenoid, or alternator?
How to test?
Starter, solenoid, or alternator?
How to test?
Senior User
Joined: Apr 2004
Posts: 207
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From: Missouri
lMy '92 has been doing the same thing since this past winter.
When I touch the pos. battery cable end to the post, it makes a big ole spark.
I have no aftermarket electronics anywhere in the truck.
I'm curious what pulls that kind of current when the key is off.
I've noticed it doing it a lot worse since winter, I have to leave the pos cable off or it'll be dead every day.
I've even tried several batteries, same result, I may do as others have mentioned, and pull all fuses one at a time, and see where the drain is...
When I touch the pos. battery cable end to the post, it makes a big ole spark.
I have no aftermarket electronics anywhere in the truck.
I'm curious what pulls that kind of current when the key is off.
I've noticed it doing it a lot worse since winter, I have to leave the pos cable off or it'll be dead every day.
I've even tried several batteries, same result, I may do as others have mentioned, and pull all fuses one at a time, and see where the drain is...
Last edited by FordTruckFreeek; May 2, 2006 at 01:45 PM. Reason: I can't spell, lo
Thread Starter
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Freshman User
Joined: Sep 2002
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From: Philly Area, PA
I actually isolated the drain to the top connection on the alternator - what is that connection? Is there any way that could prevent starting?
The lights never dimmed, there was no clicking. Just no attempt to start at all.
The lights never dimmed, there was no clicking. Just no attempt to start at all.
Senior User
Joined: Oct 2005
Posts: 446
Likes: 1
From: Germany
Sounds like you have something shorting out. Disconnect your battery (both posts to be safe). Then switch your meter to read continuity (ohms) and check between every place that the battery power goes to and a good ground. With the drain you describe, you'll probably find the short in the alternator, starter, or solenoid. Batteries have been known to short themselves out inside also so don't overlook that.
Good luck.
Dave
Good luck.
Dave
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Freshman User
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From: Philly Area, PA
Well, last night I used two screwdrivers to take the positive post to the "S" post on the starter relay... Started right up. So I think that I have a bad alternator, and a bad ignition switch. Looks like I'll have a push button starter from here on out.
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Senior User
Joined: Oct 2005
Posts: 446
Likes: 1
From: Germany
You may not be as bad off as you think. If you search for posts by me (within the last week or so), you'll see that I had a problem that someone suggested the culprit was the ignition switch actuator. I haven't taken things apart yet, but I'm pretty much convinced that that's the problem. Try to start it with the key then turn the key as far as it will go back toward you, then try again. It gets me started now, but I'll have to tear things apart sooner or later. If you're still having a power drain, that won't be your only problem. You'll usually find that it's cheaper and safer in the long run to track down a problem and fix it, instead of trying to compensate for it (push button starter switch)
Good luck,
Dave
Good luck,
Dave