Interesting Electrical Probem

[Rem701]

I have a 71 GMC Jimmy that is located in Austin, TX. I keep it in a garage full time with the top off. I am out of town during the week so typically only run it on the weekends. I tried to run it on the weekend of January 28th and it seemed like there was no power to the fuse block at all. Lights did not work, would not start, radio had not power with the key on etc. I looked at the fuse block and I have what I believe is the electric choke lead, which is non factory, for the edelbrock 1406 plugged into one of the two ignition unfused plugs, that wire was unplugged for some reason. I also have another lead plugged into the second plug next to that one, which was also unplugged, I am not sure what it is for but I think it is factory. I think it is possible that i could have some how kicked these wires out of place. The reason I brought up the date was because that particular weekend the weather was unusually humid, so much so that there was moisture on the windshield. I have been keeping the vehicle in its current location since September and I have never seen that happen. I was not in town last weekend, so I did not mess with it then. During last week Austin had some crazy freezing rain weather that caused city wide power outages. It never moved. Last night, Friday, I came into town and tried to start it up. All of the electrical system worked like it always had. The lights came on with the switch, the engine turned over, and the radio behaved like the battery was disconnected and reconnected. Then engine took a little bit of time to start but just like it has been. The only thing was I think the chock was open because once I got it started it ran at pretty low RPMs. Then I ran it for a little while and everything seemed fine except for the oil pressure gauge was slightly erratic, which I have never noticed before. I drove it today, Saturday, and when I started it, the chock did seem to be engaged because it was running pretty fast. I let it run for a few minutes like that and then hit the accelerator to make it stop. I then drove it a few miles stopped, picked up some food, and then got back in it and everything was still fine. Sorry for being so long winded but I guess my question is, what can cause total lack of power to the fuse block, and then start working again? Would the moisture cause any of this? Is this related to grounds? Any incite would be appreciated. Thanks in advance.

[RustyPile]

Just taking a wild guess and taking into consideration the lengthy storage period and exposure to humidity...

I don't have a clue how those wires became disconnected, wires don't just unplug themselves, they need some sort of outside help.. I lived in Austin twice in my lifetime. Once in the mid-'60s courtesy of the U.S Army. And again in the mid to late '80s, courtesy of myself.. I don't remember seeing any electrical gremlins running around during that time, but you never know. You'll need to restore power to the choke...

You didn't mention any weirdness in any other electrical items.. -- i.e. horn blowing when turn signals are activated.. Hi beam indicator on when headlights are on dim. Things of this nature are usually indicative of loose or bad body grounds. With that much total loss of power to so many circuits, I don't suspect body ground issues.. But the ground loss COULD be at the main ground cable at the battery. First thing I'd try is thoroughly cleaning the battery post/cable connections..

Just a friendly suggestion.. You'll probably get a better response to this thread if you post it in the ELECTRICAL FORUM.. Contact one of our administrators and ask to have it moved...

[Classics Fan]

I had a similar problem with a different vehicle, 1968 LeMans. Complete and total loss of 12 volt power to the fuse block. I traced the cause to a loose wire on the ignition switch. I don’t know if the wiring from the battery to the fuse block is the same on a Jimmy but it’s something to consider. I’d suggest finding a wiring diagram and trace the electrical path to check all connections. If it happened once it will likely happen again.
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[MikeB]

You might want to take a look at the firewall connector. To unplug it, loosen the screw in the middle that secures the connector to the fuse panel.

When it's out, turn it around and make sure there is voltage on the terminal tied to the red 12 gauge wire (on the right in the photo). This wire powers the ignition switch and the fuse panel's BAT bus.

The red wire originates at what GM calls a "splice", which is a soldered junction that ties it together with a wire from the battery (thru a fusible link) and the alternator output wire.

If you have voltage on the connector terminal, the problem could be a poor 50-year-old-connection when it's plugged into the fuse panel. After disconnecting the the battery ground cable, you can try cleaning the terminals with contact cleaner and a brass brush, or even a contact resurfacer, a.k.a. burnishing file.

Have to say it was tough reading through you post. Using paragraphs makes things much easier to read.

[Tmend]

Check the small glass fuse connection off of the passengers fender small junction box. Al’s check the wires at that box and from that box to the battery .