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Anomalous voltage issue 1985 D100
https://www.slantsix.org/forum/viewtopic.php?f=28&t=62580
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Author:  BamaFan95 [ Wed Jul 11, 2018 8:29 am ]
Post subject:  Anomalous voltage issue 1985 D100

Hi, guys. How's it going? I have a strange issue that has been happening with my '85 D100 /6 automatic and hoping for some advice on my next course of action to locate this problem. For the past 6 months, I've been chasing an odd issue with random voltage drop on this truck. I will try to provide the most in-depth description of the issue as I possibly can:

It started one day when I went out to the truck to start it. I turned the key on and noticed that my dash lights were very dim and no buzzer. I popped the hood and checked the terminals and they looked good. I took them off, repositioned them and fastened them back down, but to no avail. I then started to mess with the shifter and noticed that if I jiggle the shifter (without ever moving it out of the park position), my dash lights in the truck began to flicker in synchronization to me moving the shifter. My clock also flickers from dim to bright as I do this, as well. This is where it somewhat baffles me...

Me and my Dad both have been scrutinizing every connection we could think of. We replaced the terminals, battery, checked the starter solenoid and it is working just fine. Another thing that I have noticed is when the lights are dim, the starter will make no effort to turn over, but if I jiggle the gear selector a bit, it will drag like the starter is weak. But, if I find the exact PERFECT position to hold the gear selector in (not easy to find 99% of the time), the lights on the dash will be bright and the starter will turn over flawlessly.

Thinking the neutral safety switch might be the main culprit, we bypassed it and once again, to no avail. The voltage issue exists when it is running too, and sometimes the poor connection (when running headlights at night) is so bad when I come to a stop, it tries to stall out and all of my dash lights go out and headlights nearly go completely out. I can watch the headlights exhibit the same flickering problem if I turn them on and jiggle the gear selector. What could this be?

So after replacing the battery, the terminals, checking wiring, checking starter solenoid, bypassing neutral safety switch, we are not sure what to examine next. Has anyone experienced this problem before? I will also try to post a video link to YouTube very soon to illustrate this problem. Thanks guys in advance for any help!

Author:  Charrlie_S [ Wed Jul 11, 2018 9:01 am ]
Post subject:  Re: Anomalous voltage issue 1985 D100

Possibly a bad ign switch, or the wiring in the columm.

Author:  BamaFan95 [ Wed Jul 11, 2018 2:28 pm ]
Post subject:  Re: Anomalous voltage issue 1985 D100

Charrlie_S wrote:
Possibly a bad ign switch, or the wiring in the columm.


Thanks for your reply, Charlie. We will be looking into that in the next few days. I would assume that the column will need to come out to gain access to the switch, correct? Thanks, again!

Author:  Charrlie_S [ Wed Jul 11, 2018 4:45 pm ]
Post subject:  Re: Anomalous voltage issue 1985 D100

No need to remove the columm. Do you have a tilt wheel? If non tilt it is duck soup. Just watch how everything comes apart, so it can go back together the same way. Remember there is a "master" spline on the shaft, and the steering wheel must match that, or you will mess up the splines. Just did my 84 D-100. Changed the ign switch, and dir switch.

Author:  BamaFan95 [ Thu Jul 12, 2018 10:05 am ]
Post subject:  Re: Anomalous voltage issue 1985 D100

I have the non-tilt wheel. I'm glad to hear the column can remain in place. I will be updating on this, soon. Thanks!

Author:  BamaFan95 [ Mon Nov 05, 2018 9:15 pm ]
Post subject:  Re: Anomalous voltage issue 1985 D100

Just thought I'd update this in case it helps anyone. Sorry I took so long. I ended up not changing anything and it randomly quit giving problems from late July until last month. I started it late in the evening to take it for a drive and turned on the headlights on and bam everything black and engine shut down.

I took a look at my battery terminals (cheapos bought at O'Reilly's) and they were already getting corroded, so I cleaned them and now for some odd reason, it seems to be ok with no change (as far as I can tell) in voltage when moving the shifter at the moment (weird). I'm beginning to wonder if I may need a higher quality set of battery terminals and that may just solve the problem.

Author:  Badvert65 [ Thu Nov 08, 2018 1:51 pm ]
Post subject:  Re: Anomalous voltage issue 1985 D100

You might also make certain that none of the battery cables are rubbing anywhere. Especially around the steering column/linkages.

Author:  coconuteater64 [ Mon Dec 10, 2018 7:04 am ]
Post subject:  Re: Anomalous voltage issue 1985 D100

My 84 had bizarre electrical gremlins too. I changed the battery cables, ignition switch, cleaned all the grounds, and the voltage regulator. The alternator was already new. I suggest going over each wire one by one and cleaning the grounds, as that's the easiest and cheapest place to start.

Author:  BamaFan95 [ Mon Apr 29, 2019 3:01 pm ]
Post subject:  Re: Anomalous voltage issue 1985 D100

Hi again, everyone. Thanks for all of the suggestions. The issue FINALLY (I believe) showed it's ugly face yesterday. My Grandad was the previous owner to this truck and he had done some wire hacking on it that I was not aware of. After my last update, I continued for a while having the same issues of low voltage, starter didn't want to turn over and also the wierd issue of voltage changing as I wiggled the gear shifter. New terminals did help, but it was very short lived. The low voltage problem I was having was kind of intermittent. A lot of times it'd be fine, while other times, it was really bad. Well yesterday, the source I believe of this problem finally showed up and boy, was it a doozy.

So the picture here is of a bolt with metal wire wrapped around it. There is a 12v wire that comes out of a boot at the driver side fender near where the intake tube enters the fender, containing many electrical wires and it goes through the firewall and I believe it is the main ignition power source. At some point, my Grandad had cut that wire in half and reconnected it, but instead of tying the wires back together directly and putting a wire nut on it, he touched both ends of the wire to the bolt and wrapped that metal wire around it to hold the 12v wire firmly to the bolt, using the bolt I'm guessing as basically an electrical contact? I really don't know what to make of it.

Image

So anyway, yesterday, I try to start the truck and it does it again. Low voltage, dim dash lights and the starter won't even turn over. I try and try to get it to turn over, when suddenly this influx of white smoke and burning electrical smell came from under the hood. By now, you can guess what it was. I cut that old bolt out and used 10 gauge elecrical wire to tie it back together and lo and behold, it seems to be perfect. Time will be the tell-tale factor in this. For now though, it is working great! Thanks again for all suggestions y'all gave! I'm hoping this is the last update I have to do on this topic, lol.

Author:  coconuteater64 [ Tue Apr 30, 2019 7:36 am ]
Post subject:  Re: Anomalous voltage issue 1985 D100

Good thing you caught this before it let all the smoke out of the wiring! I hate deciphering someone else's engineering.

Author:  BamaFan95 [ Tue Apr 30, 2019 9:43 am ]
Post subject:  Re: Anomalous voltage issue 1985 D100

coconuteater64 wrote:
Good thing you caught this before it let all the smoke out of the wiring! I hate deciphering someone else's engineering.


It was definitely cooking good when I found it! That bolt was also wrapped in electrical tape and it had melted to the bolt. It was fun just getting that off. I'm glad it ended up being much easier to find than it could've been. I was afraid the issue was going to be in some random place that would be nearly impossible to find.

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