current leak? short circuit? possible causes?

[getrolfed]

I just replaced both batteries and my alternator for the third time. When I reconnect the batteries the terminal "sparks" indicating a current leak.

My truck has no options and I can't think of electrical conponent that should draw any current with the truck not running.

I'm wondering if I might have a defective relay or some such thing. I would imagine that over time my batteries will be drained completely, if I don't drive the truck.

Does anyone have any ideas of where to look?

[action4478]

Glove box light ?

[bugman]

There are a couple of things that are running 24/7 on your truck such as the radio's memory/clock also I believe a circuit in the computer. It all depends on how big of a spark that you got when you reconnected the batteries.

[angst]

If your talking about a spark at the terminals as your re-connecting the battery terminals it's not a problem IMO. The spark is current arcing across the loose connection before its fully clamped down.
If anything I would say its an indication you have healthy current.

[getrolfed]

I have an aftermarket radio/CD player (never did figure out how to set the clock). It would make sense that the radio would use some current, but very little.

The spark I'm getting is rather large; almost leave a burn mark on the battery terminal. My impression is that there is quite a bit of current being drawn, however, I do not have a DC clampmeter to check it. I did check my glove box light and it does not stay on.

[RoGrrr]

Follow your heavy battery lead to the solenoid. You will see the high current lead going from the positive terminal on the positive post on the batteries going to the big terminal on the starter relay. That big terminal will probably have several other lead wires (terminal rings with wires) on it.

Remove ALL the leads and put the battery lead back on it with those other wires OFF the terminal. Tighten the nut on the solenoid terminal. Put the nut back on so the battery lead doesn't get loose and short to ground !

Now, take the first loose wire/terminal and touch it to the battery post on the solenoid. See a spark ? No ?

Try the next one. See a spark ? If so, you found a lead that is drawing current. If not, go to the next one. Typically, there are 3 or 4 leads on that terminal plus the battery lead.

Now that you have found the wire that is your culprit, get an ammeter and see how much current it is drawing. Then get a wiring diagram, or talk with a knowledgeable mechanic WHO KNOWS ELECTRICITY ! THIS IS IMPORTANT. He must be able to trace out circuits. He must know electricity.

I had a bad relay that controlled the fuel pump in my F150 gasser. The pump ran all the time even when I shut off the key, drawing 0.4 amps and killed the battery.

Roger

Originally Posted by getrolfed

I just replaced both batteries and my alternator for the third time. When I reconnect the batteries the terminal "sparks" indicating a current leak.

My truck has no options and I can't think of electrical conponent that should draw any current with the truck not running.

I'm wondering if I might have a defective relay or some such thing. I would imagine that over time my batteries will be drained completely, if I don't drive the truck.

Does anyone have any ideas of where to look?

[Larry S.]

Electronic equpment, like your aftermarket radio, often have a large filter capacitor at their power input. The spark you are seeing may be the charging current for this capacitor. This charging current is a very short burst of current that goes to zero as soon as the capacitor is charged. I seen this many times on modern vehicles. To see if you do have a leakage current that is draining your batts, connect an ammeter in series with the battery lead and see what the steady state current is. Start with a high current meter, I use my digital VOM on 10 amps, then reduce the current range if you are getting a low reading. Steady state current, with no hod or interior lights on, should be less than 100 milliamps (0.1 amps).