I have always found the information I need by searching the forums, but this has me stumped so it is my first post. Four or five times a month over the past three months there is no power when I try to start the truck...no lights anywhere, no horn, no glo plugs...just nothing. Just like the batteries have been disconnected. After a while, from ten minutes to overnight in one case, it starts right up. Sometimes this happens when the engine is hot, sometimes after the truck has been sitting all day-it doesn't seem to matter. I got a list of grounds from Alldata and cleaned all the grounds and replaced questionable looking connections and wires in the engine compartment and under the dash. I pulled the steering wheel and dash front and looked for bad connections in the steering column and behind the dash and replaced the ignition switch, but haven't found anything that helps. The last two times this happened the truck started, then died instantly when I switched on the headlights. Anyone have any suggestions? My wife refuses to ride with me anymore since it stranded us at HEB one night with a hundred dollars of groceries in the back seat. This is an '86 F250 Lariat diesel w/ c6 transmission.

 

Sounds like you covered it pretty well. I would take a test light/voltmeter and the next time it's dead start at the battery and work your way thru till you lose power. With a complete loss of power, you shouldn't have to go far to find it.

 

My GUESS is the ground lead from the battery to the frame/engine block. I'd replace it if it's the original. One test lead on the hot CABLE (NOT battery) and one on a ground point (engine block). If no voltage, replace ground lead.

 

Thanks for the quick response and ideas. I'll start carrying my multitester with me. I cleaned up all the battery cable ends (replaced two) and grounds, but the cables themselves are pretty sorry. I've ordered some from LMC because I couldn't find any in town. I hope that's it. On the up side, all my lights are brighter and the starter spins faster.

 

> I've ordered some from LMC because I couldn't find any in town.

Next time try a West Marine to make cables for you. Just use the 5/16 or 3/8 eyelets on each end and put marine terminals on the battery posts.

> then died instantly when I switched on the headlights

To me this says bad headlamp switch or bad flasher relays. Disconnect the battery! Pull the dash and look at the switch. The big fattest wire (usually red or red/black strip) might not be making contact all the way into the headlamp switch because it backed out of the connector.

 

I replaced the cables (all of them) Monday and the headlight switch. Everything worked so well I thought I had it, but on Friday when I turned the key to go to work...nothing. I grabbed the test light as gfw1985 suggested and it didn't take long to find a connector just upstream of the fusible link to the cab power that was melted internally-looked fine outside. Cut it out and soldered the wires. It's only been three days, but I think that was it. Thanks everyone.