Electrical issues, possibly a short? - Ford Bronco Forum
 
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post #1 of 16 (permalink) Old 12-25-2016, 04:03 PM Thread Starter
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Electrical issues, possibly a short?

First things first, Merry Christmas!!!

I am hoping to pick up some advice on where to start looking to resolve an electrical issue. The background and vehicle;
1994 Bronco, Eddie Bauer 5.8 (new Ford motor I replaced last year) I am the original owner.

I had some issues with the ignition recently (key spinning around and failed to start occasionally) so I replaced that with no issues. However the starter which was starting to go bad decided it was time to fail completely so I replaced that. So far so good with those two parts replaced, went and checked the battery and cables all good there, battery and alternator all check out charging and holding a charge.

Then today the truck wouldn't start, just dead, no cabin lights no dashlights, check engine light, nothing. Checked the battery it's charged up and good but I noticed the ground was hot to the touch. So I am assuming a short somewhere. Here's where I am a bit limited, I don't know where to start troubleshooting a short like this, It's very possible that this may have been going on for sometime and I just haven't noticed it until today.

I can be methodical and follow schematics but I really don't even know where to begin other than starting at the battery and working my way back from there. I'm thinking there are a few other well known points of failures that I might want to check out before I start opening up wiring harnesses and and testing wires and would gladly welcome any suggestions or pointers.

Thanks in advance for any advice you all may have!
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post #2 of 16 (permalink) Old 12-25-2016, 05:08 PM
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Yo Watchman,
Are batty posts, positive and ground and cables clean and tight? Check all ground cables to block, intake manifold, firewall, hood and frame.
Was battery load tested?

Short Circuits, Common Locations TSB 95-02-11 on 94-95 Bronco & Trucks; See J. No start


Canister Purge Solenoid Valve Pic by Seattle FSB

Battery Drain; "...Disconnect the positive clamp on your battery but take care not to touch the body metal with the wrench when doing this. Now connect an small light between the + terminal and the clamp. Put the clamp on a rag so it can't touch the sheet metal. If any drain is present the light will glow. Or you can check the amount of drain with an small ammeter. An drain of 1-2 Watts can be tolerated. Next pull the fuse for the mechanic clock and the radio. Still any current flowing (light on)? Ok, so you really have a problem. Now start pulling the fuses in the fuse box one by one until the light goes off. This is the circuit in which the problem lies. Check your manual or the indications in the cover of the fuse box to see which systems are connected to that fuse. The next steps depend on the systems concerned. Try disconnecting each one of the parts connected in the circuit. Again it's the same - when the light goes out you've found the problem. Even better than a light bulb is an buzzer. Many people have one of those annoying little rascals lying around. Use it..."

Parasitic Current Drain; here is a Test; "...you should be able to trace the "parasitic draw" on the battery in the normal way. Pull the (-) cable off & put an ammeter inline set to the 10A range (or higher if possible) to see how much current is being pulled out of the battery with the key OFF, the doors SHUT, & the hood light bulb REMOVED. Make sure absolutely NOTHING is turned on anywhere on the truck. If it registers 0 or below the meter's next range, switch it down a range until it shows some useful numbers. If it ends up being below 0.5A (500mA), then replace the battery. If it's above that, start by disconnecting all the alternator wires & see if the reading drops under 0.5A. Then move to the fuse block & pull Parasitic Current Drain Test; "...you should be able to trace the "parasitic draw" on the battery in the normal way. Pull the (-) cable off & put an ammeter inline set to the 10A range (or higher if possible) to see how much current is being pulled out of the battery with the key OFF, the doors SHUT, & the hood light bulb REMOVED. Make sure absolutely NOTHING is turned on anywhere on the truck. If it registers 0 or below the meter's next range, switch it down a range until it shows some useful numbers. If it ends up being below 0.5A (500mA), then replace the battery. If it's above that, start by disconnecting all the alternator wires & see if the reading drops under 0.5A. Then move to the fuse block & pull them 1 at a time until there's a significant drop in the reading. That's the circuit that's draining the battery. Follow it to find the problem..." 1 at a time until there's a significant drop in the reading. That's the circuit that's draining the battery. Follow it to find the problem..."

See my partially recovered Bronco web site ...Will need to clean up dead links & add many more new links some day. Thanks to Mr. Schwim!
THANKS to ALL WHO SERVE!
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post #3 of 16 (permalink) Old 12-25-2016, 05:48 PM
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Yo,
Had to rush last response.
Check ground and + cables wire strands for corrosion, damage or looseness.
Is relay securely mounted to a Rust/Grime Less section of fender?

This can also be due to a dead battery cell. Sometimes, a battery will have just one cell go bad or short out. When this happens, the battery will seem fully charged, but fail to start the Bronco, or it may start the Bronco right after charging, but then fail to crank. I had a dead cell that did same; no crank then after turning to start a few times, it would crank.

See my partially recovered Bronco web site ...Will need to clean up dead links & add many more new links some day. Thanks to Mr. Schwim!
THANKS to ALL WHO SERVE!
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post #4 of 16 (permalink) Old 12-25-2016, 06:02 PM Thread Starter
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This is great stuff Miesk5, I will be testing these steps later tonight and post back the results!

Thank you!!
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post #5 of 16 (permalink) Old 12-26-2016, 12:00 PM
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Miesk5, great post,FYI, I have had this problem twice, 1985 f150,culprit was the electric choke( relay for choke )shorted out causing the choke to stay on, !1992 ford bronco= culprit diodes in the alternator shorted out causing the drain.Good luck TR
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post #6 of 16 (permalink) Old 12-26-2016, 02:06 PM
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Yo Black Ford Xlt,
TY.
BTW and for posterity;


Bad Diode Pattern 1; This waveform was captured using the diode pattern test located in the engine tests menu. This particular alternator has a bad rectifier, causing an AC voltage to ride on top of the DC voltage signal.
This AC voltage affected the pip and spout signals (Ford primary ignition signals) causing a no code driveability problem. The fix was to replace the alternator.
...


Bad Diode Pattern 2; This waveform was captured using the diode pattern test located in the engine tests menu. This alternator, like the previous alternator, has a bad rectifier.
This is another example of how a bad rectifier can affect the diode pattern. The fix was to replace the alternator.
...


Bad IAC Waveform; This waveform was captured using the lab scope. This is a good example of how an alternator with a bad diode can affect other signals that the ECM looks at. In this case it is an IAC motor.
When viewing waveforms that have a lot of hash always look at the alternator diode pattern as a possible cause.

See my partially recovered Bronco web site ...Will need to clean up dead links & add many more new links some day. Thanks to Mr. Schwim!
THANKS to ALL WHO SERVE!
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post #7 of 16 (permalink) Old 12-26-2016, 02:36 PM
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I would start by checking the fuseable links on the starter relay.

Looking at the starter relay you will see a bundle of White wires with a Black shrink wrap band around it, these are your main power leads to the fuse box. Under that band are fuseable links. If something shorts BAD, it could burn those links. So I would check those out first.


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post #8 of 16 (permalink) Old 12-26-2016, 06:16 PM
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If your negative battery cable was hot after driving the truck, I would assume that there was too much resistance in the neg battery connection. Clean both battery connections and see if it solves your problem. If your neg battery terminal is old or one of those replacements that clamps to the old copper cable, I would buy a new terminal and cable.
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post #9 of 16 (permalink) Old 12-27-2016, 12:19 AM
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many Bronco's have seen significantly improved performance in the electrical system by upgrading neg. cable to thicker gauge and obviously, freshly cleaned connections. if you're already needing to replace... it would be a great time to bump it up a notch.

"When life throws you a curve... LEAN INTO IT!"

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post #10 of 16 (permalink) Old 12-29-2016, 09:21 AM
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Quote:
Then today the truck wouldn't start, just dead, no cabin lights no dashlights, check engine light, nothing. Checked the battery it's charged up and good but I noticed the ground was hot to the touch. So I am assuming a short somewhere.
Which ground wire was hot to the touch?
The big fat battery cable?
Or the little skinny one from the terminal to the fender, or radiator, or wherever it goes?
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post #11 of 16 (permalink) Old 01-09-2017, 04:27 PM Thread Starter
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So a big thank you to everyone for all the advice and suggestions! I am fairly confident the main issue is resolved although a smaller but annoying issue has cropped up.

So the main issue I noticed was the large ground cable from the battery was more than a little warm to the touch so I started there. After cutting the end off to replace the terminal connector I saw the cable itself had corrosion inside the sheathing so I replaced that length of cable (it was original after all). Then I replaced the terminal connector on the positive side, so far so good but the Bronco still didn't start. I tracked down a short in the starter relay so I replaced that, the Bronco started! Success right?

Not so fast, turns out that was a big part of the issue but not the full fix to the problems, the starter itself had apparently shorted and so did the ignition switch. I have no idea which problem came first or what caused what to happen but the starter was tested and definitely bad and the ignition switch had a distinct popping sound when it hit a certain position while turning it to start the truck. I replaced both and everything seems to be running properly. No more heat from the ground cable, tested both the cables while turned off and while running, battery charging everything looks good.

So after wrapping up I start backing out of the driveway and a buzzer from somewhere under the center of the dash near the floor goes off, I can't ever recall hearing this sound before. It's not the door or lights that's a different sound so while I think my main issues are resolved I'm a bit hesitant on what this new rather annoying buzzing is...

Once again thanks for all the advice, it most certainly put me on the right track and got me back up and running again.
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post #12 of 16 (permalink) Old 01-09-2017, 04:38 PM
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The sound you are hearing is the air bag box. It has also shorted out and blown its internal fuse. You can hit the junk yard and get one out of any 94-95 ford or you can attempt to fix it.


The air bag module has a green cover and is located above the gas pedal.


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post #13 of 16 (permalink) Old 01-09-2017, 04:59 PM Thread Starter
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Great pictures!

So I'm guessing by the way you say 'attempt to fix it' the best fix is to replace it. Any chance I can set it off replacing this module?
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post #14 of 16 (permalink) Old 01-09-2017, 05:23 PM Thread Starter
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Looks like there are several threads here on the airbag, thanks for the tip Jowens1126...
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post #15 of 16 (permalink) Old 01-09-2017, 05:30 PM
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the only problem with getting one from the junk yard is, it may have the same problem. They arent in the junkyard for no reason. and you cant tell by a visual inspection of the circuit board.
But I would say, you have at least a 60% chance of a junk yard module being good.
The good thing is, its easy to test. Remove your negative battery cable before disconnecting the module. Remove the old one, plug in the new one, put the battery cable back on, no buzzer = success. If you still get the buzzer, go back in for another one and tell them at the check out that one is bad.

Theres a really nice Pick and pull junk yard at the Theodore Alabama exit for Tillmans corner. I like that place. I used to go there alot when I worked right down the street from there.

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post #16 of 16 (permalink) Old 01-09-2017, 05:36 PM Thread Starter
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I know the junk yard you're talking about, been there several times. I'll head out there this weekend and try to get one.

Thanks very much!
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