Electrical failure

[switzerlad]

my '78 k5 goes completely dead electrically - no ignition, lights horn, etc. Battery is good. When this ours, I can't even jump start the engine. A day or so later (sometimes removing and then returning battery) engine will start. Have checked several circuits to no avail. Any suggestions?

 

[rampage]

Since removing the battery makes it work again it could be either bad/corroded connections at the battery terminals or bad/corroded cables under the insulation that you can’t see. If you’re really careful you could use a set of jumper cables from the battery to the starter to bypass a suspect cable, just be REALLY careful not to let it short anywhere. Do you have a multimeter and know how to use one?

 

[mechted]

Second vote for battery cables.
Also: check the junction block on the firewall. Should be +12V battery at those wires all the time. If you have one of those wires bad internally or at the connector it will cause similar problems (main power feed to the fuse block goes through here)

 

[76k5blazerr]

Another one for battery cables. Next time it does this, wiggle the terminals at the battery and see if you get power back. If you do, replace the cables.

 

[diesel4me]

Half fried fusible links can do that too...the ones at the starter that are in big red wires (that run thru a metal conduit factory) often get baked in that metal pipe and if they were ever put thru a temporary heavy short circuit and started to melt ,they can still pass some volts and amps,but not always enough to supply enough juice to the cab,ignition,etc,and let it crank over..

 

[ballencd]

I had a 87 M1009 once that did the same thing and found the firewall cables were loose and I had to tighten the clam shell between the cab and the engine compartment which pulled the connectors together and never had trouble with it again.