Tip & How-To about Ford F-150

How to tell if you have an electricl short in your vehicle

If you suspect an electircal short in your vehicle. Your battery is draining with the vehichle off not running on key in the ignition. Then you have a short currcit something that is connected to the posititve side of the battery is touching the negitive side that is not suppose to touch it If you were to take a peice of metal and touch it to the positive side of the battery and the negitive side at the same time you could see what would happen and i don't want you to try it this is for effect.But this is what is happening just on a smaller scale. Your going to need a meter like a multimeter that can read 20 VOLTS DC. Then you need to remove the negitive cable from the battery termanial and move it away so it is not touching any metal that would ground it to the main ground system. Then take your meter touch the red lead from the meter to the positive terminal on the battery and the black lead from the meter and touch it to a good engine ground like the engine block.You should not get any reading because the negtive cable is disconnected from the engine so there should be no path for current to flow. But if you do get a reading then you must have something that is hot shorting to the engine ground. It depends on how much you are reading to try to track the problem down because it could be anything electrical that is causeing the problem . The voltage is your best indacator of what to look for a low voltage .5 to 1.5 volts is going to be something that dosn't drew a lot of voltage. This is where you have to use sight and soundlook for small things that don't work or have been giveing you problems like a side mirror or an interior light thats not working correctly. You can also use the fuse box to help youby unpluging one fuse at a time to see if the problem goes away the cause will likely be on or realated to that curcuit this greatly cuts down the number of possible compounts that could be related to the problem. .will complete later

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runs fine for a wile then dies battery drained

A car battery can run down for any of several reasons:
  • You accidentally left the lights on or some other accessory that pulls power from the battery even when the ignition key is off.
  • The battery is not being recharged while the vehicle is being driven (you have a charging problem)
  • There is a key off parasitic electrical drain on the battery because a relay is sticking, a module is not shutting down, or there is a shorted diode in the alternator.
  • Your battery is old and will not hold a charge anymore. The battery needs to be replaced.
Most of the time if the battery is fairly new and keeps getting drained have the mechanic check the alternator if its charing the battery.
Thanks for using Fixya.

Mar 14, 2011 | 1998 BMW M3

1 Answer

How do I find a electircal short. After sitting

You have a draw, not a short. Disconnect the positive battery cable, and put a 12v test light between the cable and pos. batt. post. Light will illuminate indicating power is being requested by a circuit. Start removing fuses one at a time until the light goes out. That will be the draw circuit. Check the items on that circuit for the one that isn't shutting off.

Dec 22, 2009 | 1983 Oldsmobile Cutlass Supreme

1 Answer

changed the key ignition in my 2000 gmc jimmy and now the battery light and odometer milage light stays on and drains the battery This all happenens when the truck is turned off. When the truck is running the battery light goes off. Could this be a short in a wire, if so where? or could something have been damange when I changed the key cyclinder

The ignition switch(this is the electrical portion) is out of time. It needs to be removed, reindexed(notched teeth on top of switch-rotated a couple spots) and reinstalled. When it is installed correctly, the tell tale lights will not be on, you'll have accessory and the vehicle will start in the crank position. You don't want any lights on when the key is out of the ignition.

Oct 01, 2009 | 2000 GMC Jimmy

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