Mystery Short

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Oct 30, 2001 | 08:29 AM

sitron

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Mystery Short

Whenever I park my BII the battery will drain. I figure that there must be a short somewhere, but I cannot find it. It started out as an intermittent problem and has steadily worsened. I have to unplug the battery everytime I park it now, or else it goes completely dead. I have put in a new alternator/regulator, new positive battery cable, the ground looks ok, changed a couple vacuum relays, and have tested everwhere for a short. I tested the battery with a battery powered test light, from the ground to the unconnected positive cable and it didn't light. Then I ran the same test with an OHMs meter and the needle would go almost all the way across, so it appears not to be a direct short, but there is resistence. Is this normal?
Also, I don't know if this is related, but the engine cuts out (missing) while driving. No method to its madness....any speed, any RPM, sometimes runs great and I think it's fixed, then it starts missing again out of nowhere. Maybe a bad relay somewhere?

Oct 30, 2001 | 01:32 PM

Avanti

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Joined: Aug 2000

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From: home

Mystery Short

One way to help narrow down your short is to pull a fuse(one per night) to see if the battery stops discharging. If no change in the morning reinstall the fuse and pull another one the next night. I have seen cars batteries discharge very slowly thru a brake light switch, door jam switch etc and the light did not glow bright enough to tell the light was on. After you have determined which leg of the circuit is discharging try to determine what all is on that leg, headlights , tail ect. Than try to determine where all the wires are and systematically check all of them for cuts in the wire were possible.If none are found disconnect each device at a wire connector & over night see if their is a change. Also disconnect the positive side of the battery and on light circuits pull the bulb and do an ohm reading from inside the connector. You should get a ground only on one side. The missing of the engine is part of the ignition system and should be different. I would check the spark plug & distributor wires.I once had the problem with an older car and it was a wire in the distributor that was toutch and shorting out. You could go at over the speed limit and it ran great slow down and the wire shorted out. Hope this helps.

Feb 11, 2002 | 10:19 PM

tiggrdave

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Joined: Feb 2002

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From: Leesburg USA

Mystery Short

You should check the alternator wiring going into the wiring harness. I replaced my alternator on 1987 BII and experienced the same problem. The wires had gotten hot (normal use) and the insulation had cracked and intermittently the conductors would ground out. There are also several splice points in the harness where several wires are soldered together, and the insulation in them had also cracked.

If you look at the wiring harness connectors beneath the master cylinder, you may also find that some of the wires have exposed copper where the insulation has pulled back. These were the cause of my battery running down on this truck. I just repaired them in the last 4 days and all is now well.

dave

Feb 12, 2002 | 05:00 AM

steve_

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Mystery Short

i had a 85 b2 that did the same thing ended up being a bad ground

Feb 12, 2002 | 04:43 PM

destiny88

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From: Oshawa Canada

Mystery Short

Take the positive cable off the battery. Take a test light, hook the aligator clip to the post, then put the probe to the cable. Start pulling fuses unti you see the test light go dim if not out. Pull the interior light fuse first, because you will probaly have the door open to pull the fuses. The only thing that draws power all the time is the radio and the computer. The draw is usually so low the test light will maybe glow, not light. When you find what makes the test light suddenly not light, find what is on that circuit. If you pull every fuse and the light is bright, disconect the Alternator. If you fin the fuse and are not sure what is on it let me know.

May 31, 2002 | 02:15 PM

drpepper

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Joined: Jan 2002

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Mystery Short

i have found that on the bronco 2 and the explores have the same
types of problems with this type of problem , and i have found that it usually is one of two things , either the fuel pump relay or the power booster for the stero in the vehicles, so you might want to check there.

Jun 3, 2002 | 10:11 PM

Schmach1

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Joined: May 2002

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From: Colborne Canada

Mystery Short

Have you traced any of the wires underneath your distributor back a bit towards their sources? If you have a 2.9 like me, then there's a good chance a wire running to the EEC unit has melted to one of your exhaust manifolds. I had a wire do this once and it caused my ignition to screw up intermitently, similar to what you've described. Even though I had no trouble with the battery draining, I would tend to think as you've proposed that your short problem is related to the 'missing'. good luck!!!