Noticed the battery starting to die on the truck, so I charged it, check the voltage output at 2500rpms but its not getting above 12.5v. Replaced the alternator with a working older unit but it still didn't solve the problem. The charge light occasionally comes on but will go away. I'm also getting a static buildup on the vehicle and get a strong shock when exiting the vehicle while touching the metal frame.

Its a newer battery, past 6 months or so

 

Bad ground somewhere? It's always worth checking for a bad ground first whenever you have any electrical quirks.

Your truck (nice Chinook!) may be old enough that the charge controller is a separate part, not attached to the alternator. Could be it's going out and the alternator is fine.

And of course check the battery connections for corrosion or fraying. Even if you can't see it, it could be bad. New battery cables aren't too expensive.

 

Other thought. Since it is an RV version of the truck, it would likely have the 2 battery setup under the hood. The extra battery was there to run accessories in the camper, either direct DC electric stuff, or through a voltage inverter for 110 volt AC items. The truck will run & start fine if you're only running one battery installed, but maybe part of the "unhooked-up" positive side of the other battery circuit is grounding out somewhere? I'd have a good look around & make sure the second battery connections are insulated & isolated, if you aren't running the second battery.

The '77 should have a separate voltage regulator; 83 is correct on that. As far as I know there is only one of them, even in the dual battery RV versions. It should be located on the driver's side inner fender wall. It grounds through the two bolts that hold it to the fender. I'd also check those for any rust, dirt or corrosion. I also agree with 83 about checking the grounds & replacing them if a voltage drop test shows any resistance above 0.1 Ohm. The ground wire/cables can have too much resistance due to age & metal fatigue, causing all kinds of weird electrical gremlins. I had this problem in my '78 that had the original ground cables. The two stock ground cables on the '77 should be battery negative to passenger side motor mount, & rear of cylinder head to firewall on driver's side. There might also be a third ground cable for the second battery hook-up.

Beyond that, make sure the battery (or batteries) are secured & not able to move around, & that nothing from the positive electrical side is directly touching metal (ground) on the truck.

 

About the voltage regulator... I replaced it with the alternator but never got around to securing it very well, it was a little loose because the previous guy used an old bicycle brake shoe with a nut on it through the fender for one side and the other bolt was broken off. I didn't have a way to get to the store the last time I had done it so I had just reused his janky fix. Today I purchased some new hardware and mounted it properly, re-wired the negative battery cable to the new terminal (it had a slight amount of fraying around the connection) and it still didn't change anything. So I put the older voltage regulator on and its still giving the same problem.

However I decided to pull all the fuses under the dash, except the engine. It ran for about a few seconds and shut down. I could re start it and hold the gas to keep it alive. No shock from the door. Pushed them all in one by one and as I got to the TAIL fuse i received the shock on the door right when it made contact. Pulling the fuse makes it run different and dies quickly when not gassed--its just me so I couldn't go check to see if the voltage at the battery changed when the TAIL fuse was out.

 

Just to be clear, with the TAIL fuse in place, the truck runs fine? You don't have to keep on the gas to keep it going? If so I don't think your charging system is causing the problem. Considering that when you have the TAIL fuse pulled you aren't getting the shock, that narrows that problem down to the Taillight circuit. Sounds like you have a short somewhere in that circuit, possibly a bad ground in the taillights like 83 said. On the regular Pickup the taillights are grounded to the bed body. Since your taillights might be mounted to fiberglass (a non-conductor) there may be some dedicated ground wires for them that may be the problem.

IF the truck runs normally with the TAIL fuse in place, but will start, run for a few seconds then die with the TAIL fuse removed, I think I know what that is about. Checked some wiring diagrams it looks like the fuel pump circuit is a part of that circuit. Pulling the fuse does not allow power to get to the fuel pump with the Ignition Switch in "RUN". The fuel pump will get power with the Ignition Switch in the "START" position (engine cranking), but when it starts & you let go of the key it snaps back to "RUN". So no power is going to the fuel pump to fill the carb's fuel bowl, engine uses up the fuel, then dies. Having to "get on the gas" to keep it going after start could be nothing more than the higher engine speed feeding vacuum back into the fuel line, drawing just enough fuel to keep it going, even with the fuel pump not electrically working. You can draw fuel through a dead electric fuel pump so it's possible.

 

Toyota motorhomes are notorious for bad tail light grounds. Doesn't mean it'll solve your problem, but I'd almost be surprised if you didn't have a bad tail light ground unless someone previously cleaned them up. I had to work on mine with my old motorhome.

 

I forgot that my tail lights have wires that look like string cheese. The wires go underneath the thing for some reason and get nothing but abuse from the road. I'll work on those next and see where it leads me.

 

Sounds familiar...

As cool as they are, they were sort of just slapped together without too much thought.

 

That is too bad that the coach builders didn't continue Toyota's quality into their builds.

However, that just means that you can make improvements along the journey!

 

Yeah. I mean they obviously did a decent job, or these things wouldn't still be on the road. But as you start digging into them, you see a lot of stuff that's at minimum a head scratcher, but often enough to really make you mad.