Y'all might recall from a couple pages back, in July, I shared that I was fighting some electrical gremlins with my 40. Specifically, I was seeing very high voltage, blowing a particular fuse, and discovered some melted wires to the alternator. Today, I believe I can declare victory, but it wasn't without a good bit of head scratching.
I started by repairing any damage to the wiring harness. However, to my surprise, that fix did nothing to improve the over-voltage or engine fuse blowing. Keep in mind, these two problems presented at the same time, so in my mind they were totally linked. It was time to fire the parts cannon.
I ordered and replaced the voltage regulator. That didn't change a thing. I educated myself on manipulating the old-school external voltage regulator, but even after those adjustments I couldn't make clear headway. I took the alternator to town and had it checked out, and it was, in fact, charging (too well!) but that didn't stop me from ordering a new one. At this point, I was stumped and abusing all my 'phone a friend' privileges when this one:
https://instagr.am/p/C2NlvRwvxFD
asked me if I had a fusible link and if so what condition was it in. Well, I do, but I'd never looked at it closely before. When I pulled the connector apart I discovered that there was corrosion on the internal contacts. I cleaned those up, and to my surprise VOILA, my over-voltage condition disappeared. I had been singularly focused on bad GROUNDS causing that problem, not necessarily a poor positive connection from the battery, nevertheless, there it was.
Now that I was seeing 14.8V instead of 17V I thought all my problems were solved. Not so fast my friend! A couple test drives that ended in me sputtering home with the choke half-out said I was actually faced with a two-part problem. Next, I started unhooking everything on the engine circuit not named "idle control solenoid' to try to isolate the issue. The first thing on my schematic was the emissions VTV (vacuum transmission valve), but since my truck is desmogged all I have is the socket where it plugged in. I checked that out and sure enough... the PO had tapped into the power wire of the long-gone VTV to run something else that isn't there anymore (possibly a fog light relay). The wire was abandoned when he removed whatever he borrowed the power for. It was this many years of owning/driving my truck that a lone abandoned wire worked its way down and was shorting to ground when I would drive. How was I lucky enough that this problem didn't present itself at 13k feet on top of Imogene???
Since I fixed all that, I have logged about 50 trouble-free miles in the last few days. I re-installed my old original voltage regulator (since there was nothing wrong with it), fixed up all my wires, my ammeter behaves normally, and I am consistently seeing 13.5-14.8v; just like the FSM calls for. To top that off, I have a new alternator and external voltage regulator to set on the parts shelf. Those might come in handy someday.
Sorry for the long post, but this thread was due for a bump! Next I need to fix a cam position sensor issue on of these guys, and it's obviously not the green one.
I started by repairing any damage to the wiring harness. However, to my surprise, that fix did nothing to improve the over-voltage or engine fuse blowing. Keep in mind, these two problems presented at the same time, so in my mind they were totally linked. It was time to fire the parts cannon.
I ordered and replaced the voltage regulator. That didn't change a thing. I educated myself on manipulating the old-school external voltage regulator, but even after those adjustments I couldn't make clear headway. I took the alternator to town and had it checked out, and it was, in fact, charging (too well!) but that didn't stop me from ordering a new one. At this point, I was stumped and abusing all my 'phone a friend' privileges when this one:
https://instagr.am/p/C2NlvRwvxFD
asked me if I had a fusible link and if so what condition was it in. Well, I do, but I'd never looked at it closely before. When I pulled the connector apart I discovered that there was corrosion on the internal contacts. I cleaned those up, and to my surprise VOILA, my over-voltage condition disappeared. I had been singularly focused on bad GROUNDS causing that problem, not necessarily a poor positive connection from the battery, nevertheless, there it was.
Now that I was seeing 14.8V instead of 17V I thought all my problems were solved. Not so fast my friend! A couple test drives that ended in me sputtering home with the choke half-out said I was actually faced with a two-part problem. Next, I started unhooking everything on the engine circuit not named "idle control solenoid' to try to isolate the issue. The first thing on my schematic was the emissions VTV (vacuum transmission valve), but since my truck is desmogged all I have is the socket where it plugged in. I checked that out and sure enough... the PO had tapped into the power wire of the long-gone VTV to run something else that isn't there anymore (possibly a fog light relay). The wire was abandoned when he removed whatever he borrowed the power for. It was this many years of owning/driving my truck that a lone abandoned wire worked its way down and was shorting to ground when I would drive. How was I lucky enough that this problem didn't present itself at 13k feet on top of Imogene???
Since I fixed all that, I have logged about 50 trouble-free miles in the last few days. I re-installed my old original voltage regulator (since there was nothing wrong with it), fixed up all my wires, my ammeter behaves normally, and I am consistently seeing 13.5-14.8v; just like the FSM calls for. To top that off, I have a new alternator and external voltage regulator to set on the parts shelf. Those might come in handy someday.
Sorry for the long post, but this thread was due for a bump! Next I need to fix a cam position sensor issue on of these guys, and it's obviously not the green one.
