Possible Electrical Short?

So I'm new to posting here, but not new to the site at all. Used the forums quite a bit for advice, but I can't quite seem to find any other posts with this situation.

I was driving a few days ago and the tach and speedo stopped working, and the rear diff lock light came on (this truck doesn't have a locker), so I figured it was a short or a fuse...found the instrument cluster fuse burned, so I replaced it and everything seemed to work. A couple days later, the same thing happened, except this time the entire truck died as well...and I mean completely dead...no hazards, no dome light, nothing. I figured the fusible link at this point, but I waited about 10 min and everything worked again. I fired up the motor and then it died a few minutes later again.

Other information that seems useful, I just don't know what it means....when it dies and I wait a few minutes, if I turn on the hazards, they work at first, but then slow down and then die completely. I started checking resistance to the different circuits in the fuse box and almost all the circuits read extremely low resistance except the ACC circuit which is about 6 times higher resistance than all the others. This isn't the fuse that keeps blowing.

I'm just looking for advice on what my next step should be or where to look next. I've been checking grounds and they all seem okay. I pulled the dash to check wires for the instrument cluster and the cig lighters and no obvious burned wires or discoloration.

Thank you for any help y'all may be able to provide.

 

Seems like a strange suggestion but have you verified that your battery is good? An internally shorted battery can cause all kinds of weird problems. Been there myself.

 

The battery is holding a charge through all of this. While I haven't actually tested it, I have no reason to suspect the battery at this point...although I will say I checked the voltage of the battery after the "death" and monitored it. When the vehicle dies, the battery is around 11.6 volts. After I let it sit for a while after the death, the voltage was back up to normal (over 12 volts) I've been leaning towards a short of some sort that is draining voltage during the death march but am willing to replace the battery if that may fix the issue.

 

11.6 volts is too low. The battery will naturally build up some voltage while it sits idle, so I'm not surprised that it shows over 12 volts after it sits for a while. Could be alternator or battery. Beg, borrow, or steal a known good battery and check voltage with the truck running. It should be 13.4 volts or more. If it's less, the alternator has problems, which can be caused by a shorted battery. I burned up 3 alternators before I figured out my battery was bad. (Luckily, I had spares on the shelf). Charge your battery over night and get it load tested. Also do a hydrometer test on it.

 

Search for a bad body ground. I think there is one behind the intake on the fire wall.

 

Just some random thoughts............

Pull the battery and have it load tested.

Check body ground conditions as @koditten suggests. Clean and lube with dielectric grease as required.

Consider cleaning the ignition switch, or that it may be well worn and failing. (Do you happen to have a 'janitor grade' wad of keys you use?)

 

One must remember to not go crazy with Dielectric grease as it is not a conductor of electric .

If your looking for a good conductor go with the copper based never seize

 

If you still have the factory positive battery terminal. Check were the cable bolts to the terminal. A 12mm nut holds the cable to the terminal. Clean it really good also.

 

I suspect a battery AND an alternator issue. She should run on just the alternator if the alternator is putting out sufficient voltage. The electronic ignition will not fire if the voltage is below a certain amount... 10.5 or 11 volts comes to mind. Your hazards gradually slowing and stopping is an indication that the battery or the connections are bad. What I find odd is that you can restart it after a while. A battery can "recover" if it sits for a bit but I suspect something is loose. There are 2 main buse fuses, small metal straps to be more accurtate, in the fuse box under the hood... should be a 100 amp one from the alternator feeding almost everything in the fuse box and I think an 80 amp one next to it... dont have the electrical manual in front of me so I am going off of memory.

 

I will pull the battery and get it load tested. I'll check the main fuses as well. Based on my rudimentary knowledge of the electrical system, I was leaning towards a ground or short issue, but maybe my attention is being aimed incorrectly.

Almost everyone has suggested that the battery may be the issue. Can someone please explain to me how a low voltage on a battery would cause a spike in amperage to blow a fuse repeatedly? I'm extremely naive when it comes to electrical work so I'm just trying to understand how this could happen.

Thank you all!

 

Low voltage with a fair amount of amperage draw causes heat which can also blow a fuse.

 

Here's a diagram and location of the ground points.

 

Things like this I so wish I was hands on.

Just how do you check Resistance at the fuse block ??

Trying to figure out just what you are measuring

It could be so many things causing a intermittent problem

Lots of things can work after they cool down till they heat up again

Then it might be a bunch of little problems

 

To check resistance at the fuse block. Just set meter to ohms and go from positive battery post (battery post not terminal) to positive (battery side) terminal of fuse. Try to measure the othere side of of the fuses resistance is impossible.

 

Maybe I'm completely wrong in the resistance measuring....I was just connecting one end of the multimeter to the negative terminal and then the other to the blade connector in the fuse box. A buddy of mine told me that would tell me which circuit had a problem (high resistance measurement would point to a problem in that circuit). Is there a better way to narrow down the problem area? Should I be checking voltages/amperage while the engine is running?

I did take the battery and alternator in for tests and they're in working order. Just for the heck of it, I did buy a new battery and alt to try out and the same problem occurred so I'll be taking those back as I've eliminated those as possible problems.

Jon-Thank you for the explanation and the diagram. I'm going back through ground connectors, pulling them all off, cleaning them again, and placing a little copper never seize on all of them.

 

Got it Jon. So I was measuring it backwards. I'll re-test with it on the positive side.

 

I was thinking how do you reach the battery without long leads or extensions when doing the in cab fuse block

From the OP comments about not being up to speed on electrical yet

 

Easiest way to check for a draw is to place a test light between positive battery post and positive cable. Normally the light will have a faint glow. (Radio and clock memory etc). If test light is bright. It has a draw. Make sure dome light is off and start removing fuses untill the light go's to dim. If you wiggle ground wires and light flickers from bright to dim or brighter. That ground has a bad connection.

 

Long wire and some aligator clips

 

While go-go gadget arms would have been incredibly useful, I regretfully am just a measly human so I connected a long 14 g wire with an alligator clip on both ends. One connected to the terminal, the other end to the multimeter in the cab with me and the fuse box.

I like the test light setup. I'll give that a shot now.