A short in my fuse box



1998 ford ranger

the battery keeps dieing and i have been trouble shotting it for a few months…

i figured out that on the fuse box under the hood is pulling 35 volts

so i unhook the positive turminal to the fuse box and the battery don’t die… what is my problem…

thinks for the help…


Pardon my shocked look, but how does a fuse box pull 35V, when the only power source with the engine not running has a maximum potential of 12V? If this is a true reading, then there MUST be another power source attached to the truck. Track down that 35V+ source, and you’ll find the problem.


it is readding 25 ac volts
sorry… i hooked tthe tester ine to the battery possitve and then one to the possitve wire that was diconnected from the battery… and it read 25 ac volts… then i cut the two wires running to the positve terminal and tested both… and the one to the starter was pulling 0
and the one to the fuse box is pulling 25ac volts…


One of the big problems with many Rangers is the dome light not going off, or coming back on, when the door is shut. Try pulling the bulb in the dome light and see if your battery has the same problem.


it is out…

but still that should not pull 25 volts…
my battery goes dead withen 2 hours… and after new battery #3
it still is doing it…


OK, that is just one of those things that is fairly common. So, what is NOT stock on your truck?


Battery power is 12V DC. Alternator should be regulated to a max 14.5V DC. The fuse box will always read battery power with the engine off and alternator voltage with the engine running. What you need to find is which fused circuit is drawing power, or AMPS. An old school trick is, with the engine off and key in the off position, disconnect the negative cable and use a single filament bulb, like a back-up light bulb, between the negative cable and the negative power terminal. The bulb will light up as bright as the power draw. If everything is OK, the bulb will be extremely dim to not glowing at all. If it is semi-brite to brite, there is too much key-off current draw. The next trick is to pull fuses, one at a time, and re-test until the bulb goes to extremely dim or off. The last fuse pulled is the circuit the draw is in. This should help narrow down the power draw.


It can’t be pulling 25 volts, their isn’t 25 volts there to draw on unless you have dual batteries. Plus you say 25 volts AC, auto electrical systems are all DC with the exception of the pre-rectified alternator stage.

To test battery drain, remove negative battery cable, set your multi-meter to amps and connect it between the negative battery terminal and the disconnected battery cable. If you get a reading, start pulling the fuses until the reading drops, whichever fuse you pulled that eliminated the reading is feeding the equipment that is draining your battery.


You can read an AC voltage at the battery with the engine running if the diodes in the alternator are defective. And if that’s the case, this will draw the battery down.



i did this with a volt tester

there are 3, 45’s and one 50
fuse… there really big fuses… there not regular size
and if you pull one or two of them it still killes the battery
you have to pull them all or it will drain…


OMHS,law! find a book at the library. 35volts on a 12v sys.even if you are reading amps.that thing would be dead in a mere milliseconds.if you did have a short ? you would have a blown fuse, try a tech ! sorry but you are way gone.

hope that helps


well buddy i am just tellin you what i found out… i am not tryin to piss anyone off… i am trin to get my truck fixed just like many people on here… my tester might be off or not reading right but any how it don’t matter i figured out where the draw is comin from, so what does volts have anything to do with it… i might be reading 25 watt’s or amp.s idk…


HUGE DIFFERENCE! buddy! and you are not telling me anything,A/C voltage,and D/C voltage are not even in the same realm.

think OHMS LAW! you know E.I.R (in a pie form makes a big difference…BUDDY!


well i don’t know shit about electrcal…

i can fix just about anthing on a car but i don’t like messing with electrcal shit…

and if i knew anything about it, i would not be askin you questions right now


Hey, don’t get snippy. You came to the board asking questions and without being there with you and your truck we have to get some things straight. I would think that figuring a little bit about your voltmeter would be a good thing if you have been trying to find the cause for the battery drains for a few months.


Maybe you’re reading 25 amps ? you stated the draw kills the battery in 2 hours which 25 amps will just about do it as most car batteries are rated around 50 to 60 amp hours. Now what can be drawing 25 amps ? thats a lot of current. Could you have a bad diode pack in your alternator ? If one or 2 diodes short in the alt it will kill a battery fast. Had a bad diode in my 89 Stang GT and she was pulling about 10 amps…but it would still charge the battery through the remaining good diodes at reduced capacity.

A diode only allows current to pass in one direction, when they go bad ( Short ) the battery will discharge
through the alternator windings.

Try disconnecting the heavy wire that goes from the alt output to the battery and see what you read.


now we’re getting somewhere. reread the above posts they are not playing with you,you need to read them again ,and understand what they are telling you,since you do not know electric, just a hint read the post on the test light procedure(very simple and quick test) no OHMS LAW NEEDED.


ok thinks i will try that… that seems like a more resoanable problem… if i do not get this fixed what will happen to my truck?


You will probably need to see a professional mechanic. I’ve never used the AC function to test the circuits on my car, because it is designed for DC. So, I was reluctant to try to tell you that if everything were fine, you should not read anything on AC. The only AC-possible power source is the alternator, but it uses diodes to convert AC to DC to charge the battery. I’m also leaning to an alternator problem, now.


The alternator should not have an ac output. Replace the alternator. Then, you can chase power drains. AC is bad for electronic equipment.