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27Tall T 05-01-2013 07:00 PM

Finding A short?
:welcome:Finished wiring my car (used a wiring kit) and now I find that when the battery is hooked up, the car has not run for 2-3 days, my battery is near dead. The power window switches are always lit up (which I assume they should) and nothing else seems to be live. What I'm wondering is will 4 of these switches cause my battery to run down after a few days. I disconnected the ground cable and hooked my multi meter to the ground cable and the negative side of the battery and I get a reading of 10.69 volts. I would think that this is a bit too much of a draw, if they are the problem. Any thoughts as to how I might tackle this?

33Willys77 05-01-2013 08:07 PM

Yes, had that happen. The power windows are always hot and the light up switches drain the battery.

evolvo 05-01-2013 09:08 PM

With your meter hooked up as you described you can pull one fuse at a time from the panel and observe what the voltage does. If you pull the fuse for the window switches and the voltage stays high you have a draw somewhere else. BTW, my window switches only light when the park/headlight switch is on. 10.6 V is way to much draw with the key off.

27Tall T 05-01-2013 09:40 PM

:welcome:I agree with you....almost 2 volts is too much draw for the switches, but that's the way the wiring is done (EZ wire). Switches are always live without the key. I will check the fuses one at a time and see what happens.

EOD Guy 05-02-2013 03:50 PM

Just unplug the window switches and see if you have a draw. If that is the culprit then install a relay that's pwr'd when the key is on and allows the existing circuit to pwr the windows etc......

My bet is that the alt pig tail has been crossed, my reasoning:

The draw of the lights in the switches shouldn't draw the batt down that much (unless the battery's starting to go bad)

When you lay your hand on the alt caseing is it warm?

Terminal #1 from the alt goes to the one side of the idiot light on the dash. The other side of the idiot light goes to a switched 12v source (hot when the key is in the run position) This is the exciter wire and tells the alt to start producing juice. The idiot light does not get a ground wire, it gets a ground from the internal regulator in the alt when the alt isn't spinning. That's why it lights when the key is turned to run but the engine isn't running, and it goes out when the engine starts.

Terminal #2 from the alt goes to the hot side of the wiring system, normally itís spliced into the hot feed leading to the fuse box. This is the sense wire, it tells the alt to produce more or less juice depending on the demands of your electrical system.

So if you switched them, the hot side of the elec system is grounding via the internal regulator and will drain your battery in 2-3 days.

27Tall T 05-07-2013 10:19 PM

:welcome:Sorry to take so long getting back to the problem, but the car was at the upholsters for a few days. My problem is now really getting me confused. I hooked up the meter between the ground and the disconnected battery cable. I get a reading of 10.69 volts whereupon I removed the fuse that gives power to the power windows and their switches. My reading is now 12.65 volts. Great! I disconnected the meter, replaced the fuse and hooked up the battery cable and noticed a slight spark. What gives now? Hooked up the meter to the now disconnected battery cable and now have a reading of 12.69 volts!!!! No 10.69 volts!!! Has it healed itself? Not by a long shot. Temporarily removed the meter and immediately hooked it up again. 10.69 volts again. What am I missing here? Why does it read 12.65 volts one minute and then 10.69 volts the next? This happens each time I disconnect the meter. Something is intermittently drawing this voltage and I can't figure out what it is. The radio face plate has been removed and so I don't believe that it is drawing power.

75gmck25 05-08-2013 03:53 AM

If I understand how you are hooking up the meter, you are not measuring the draw on anything when you disconnect the ground cable from the vehicle. When you disconnect the ground cable from the vehicle and measure voltage between the cable end and the battery positive you are just measuring static battery voltage. Once you take the ground cable off the car, it takes the rest of the car out of the measurement.

You are trying to use a voltmeter to measure current draw and it will not work that way. A voltmeter can only measure the voltage difference between two points. If you want to measure current draw you need to disconnect the ground cable from the battery and put an ammeter between the ground cable end and the battery negative.


EOD Guy 05-08-2013 04:03 AM

1 Attachment(s)
Sounds like you aren't gettiing complete disconnect from your window switches etc..... adding a relay to control the pwr input might solve it. I've added a dia to add a relay.

sparkchaser 05-08-2013 04:12 AM

75gmck25 is right, you're doing the measurements wrong, but the main thing you need to do is get the power windows from hot all the time to switched on with the key. The only things that should be hot all the time on your car are the "keep alive" memory circuits of the radio and engine/drivetrain computer if you have one. Horns and emergency flashers are always hot also, but I've never seen emergency flashers on a tall T.

27Tall T 05-08-2013 08:58 AM

:) Okay the first thing I will do is use an ammeter and see what my draw is. Next I will isolate the power windows with a relay and hopefully that will be the end of the draw. Thanks for the input.


27Tall T 05-09-2013 09:45 PM

:) Well the short has proven to be a draw. Couldn't find an ammeter in my junk parts, but did find a test light. When used in series with the battery cable, the bulb lights up dimly. Pulled the power window fuse and the light is still dim. Pulled the radio fuse and no more light. It seems that the power window switches and the radio are the parasitic draw and not the short that I thought I had. And so the question I have for the "EOD Guy" is where would I cut the wire and place it into the relay circuit. The wiring is literally buried under the dash and resembles a spaghetti dish at a fine restaurant, which means it will be difficult.

EOD Guy 05-10-2013 03:45 AM

Depending on which kit you used....... it may have wire numbers/labels printed on the wire etc...... It doesn't matter where you cut the main pwr wire to the window switches. My windows relays are located behind my dvr's kick panel. The only place I do not recommend, is inside the door it's self....... unless you can waterproof the relay connection.

If you are comfortable with wiring etc....... pull the fuse block apart and see if you can re-route the feed for your window fuse. ie.... right now it's on the constant 12v buss you might be able to cut it off the constant buss and put in a jumper to the switched/assy buss.

If your wiring kit is from a major player, they often have provisions for installing a relay directly to the side of the fuse blk....... it would be very easy to locate the window pwr out wire and cut it right at the fuse blk, hook it to the relay etc.......

27Tall T 05-10-2013 08:30 AM

:D Appreciate the reply. Now I have to make like an contortionist and track down this colored/numbered wire and reroute it through a relay.

EOD Guy 05-10-2013 03:44 PM

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I use the bosch type relays for everything. A very good source are Mopar type cars, they use a very small and skinny 1/2" by 1" relay for just about all their functions...... I use the small female spade connectors to plug into the relay terminals. I put a piece of shrink tubing on the bundle of wires, crimp on the connectors, place the connectors on the relay, slide the shrink wrap as far as it will go towards the connectors, then heat the shrink wrap, makes for a nice neat connection.

27Tall T 05-10-2013 09:23 PM

:) It just so happens that I do have a few of these relays (left over from ??). In a way they are better because you don't need the relay socket. Thanks again.

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