Turned off running truck, immediately no horn, no lights, no power to cab

[Whisp]

I have extensively searched this and other forms (including the evil overlord google) over the past few weeks and have found no answers, not even close, just a lot of 101 basic stuff. I may be overlooking something or some secret wording but here goes.

Ok, so-far on this trek.

1986 F350 6.9 IDI

** Not the first time this has happened. **

Truck was running and charging last night, had intermittent issue with floor dimmer switch which needs replacing. Turned off headlights, then the running truck and immediately no horn, no lights, no power to cab! However, there is 12.5volts in the engine compartment, engine will crank over if relay solenoid is triggered with small wire.

• New batteries (two weeks ago),
• New cable ends, all four (two weeks ago),
• 12.5 v DC in engine compartment (last night)
• Checked the 5 fusible links on curbside finder well near relay, all have power on both sides of link (last night). -- Yes I sealed all puncture marks with liquid tape --
• Checked power on both sides of all the quick disconnect harness fittings that were visible. (last night)

Suggestion?

 

[Thewespaul]

Check the main firewall harness connector, it may have rattled loose. Make sure all your grounds are good as well

 

[catbird7]

Ignition switch on top of steering column. Could be bad switch or mechanical connection between key and switch, or switch unplugged. What happens if you pull headlights on? Neutral safety switch?

 

[Whisp]

Thanks, I was wondering about the main harness, but was told my a mechanic it was never that! , I'll check that then the grounds.
Thanks Again

 

[Whisp]

Ignition switch on top of steering column. Could be bad switch or mechanical connection between key and switch, or switch unplugged. What happens if you pull headlights on? Neutral safety switch?

I had wondered if it wasn't the ignition switch, but the key doesn't affect the headlights or the horn, no?
Headlights = Nothing
Hmmm, If the grounds are good and the main harness/firewall quick disconnect are ok, I'll start taking the steering column apart. Oh Joy.. teehee teehee

THANKS!

 

[riphip]

Ignition switch is on top of steering wheel tube under dash. Long white bar looking. Key switch is not ignition switch.

 

[Thewespaul]

You can adjust the switch without tearing the column apart, but if you don’t have power to the horn I don’t think the ignition switch is your issue, horn should be hot at all times. If firewall connector is good make sure everything is in good shape behind the fuse panel

 

[Whisp]

Ignition switch is on top of steering wheel tube under dash. Long white bar looking. Key switch is not ignition switch.

Thanks Rick, I'll check that one out as well!

 

[Whisp]

You can adjust the switch without tearing the column apart, but if you don’t have power to the horn I don’t think the ignition switch is your issue, horn should be hot at all times. If firewall connector is good make sure everything is in good shape behind the fuse panel

Thanks Paul,
Honey-do's got me this afternoon. So first thing tomorrow, I'll check ...

1. Grounds (detach/de-rust/reattach)
   
2. QD harness @ firewall
3. Fuse panel (back)
   
4. Ignition switch

Thank all yall for the advice, I'll check these and keep thread updated.

 

[riphip]

On my 86, I had problems on the tail lights way back & had to reground the 1 single black or black-green where the rear plug for tail lights on drivers side meets. That ground is separate single wire with ring to be grounded to bottom of bed cross brace. Just went out one day and took a while to find it. My horn just quit one day & it was the spring-post to ground-ring on the underside of the steering wheel worn out.

Replace that dimmer switch first, since it may have created the problem.

 

[gerlbaum]

Ignition switch on top of steering column. Could be bad switch or mechanical connection between key and switch, or switch unplugged. What happens if you pull headlights on? Neutral safety switch?

I second ignition switch, because that is exactly what mine just did and I just replaced it to fix it. Tip: mark the old one where it sits on the column with tape and put the new one back at the same spot. It will save you from having to loosen and adjust it 900 times.

 

[Whisp]

On my 86, I had problems on the tail lights way back & had to reground the 1 single black or black-green where the rear plug for tail lights on drivers side meets. That ground is separate single wire with ring to be grounded to bottom of bed cross brace. Just went out one day and took a while to find it. My horn just quit one day & it was the spring-post to ground-ring on the underside of the steering wheel worn out.

Replace that dimmer switch first, since it may have created the problem.

Rick,
There may be something to the dimmer switch. The time before this happened, I turned on the headlights and all went south. A week or more later I got in and stopped the dimmer switch (frustration) later when I tried the key, I had power. Never drew that conclusion, thought they were isolated. Hmmm It'd be funny as all get out if that was it. I'll add that to my list of items.
Thanks!

 

[Whisp]

I second ignition switch, because that is exactly what mine just did and I just replaced it to fix it. Tip: mark the old one where it sits on the column with tape and put the new one back at the same spot. It will save you from having to loosen and adjust it 900 times.

Catbird,
Good advice, I'm all in when it comes to saving time, especially when there is a smarter way to do it!
Thanks!

 

[Whisp]

Update

A couple weeks ago I boasted that I had an EMP proof truck, I should have know better than say something like that. LoL

I got tired of fooling around with the grounds, opted to buy a ground cable from parts store, went straight from the street side battery ground to the bolt where the Stanadyne filter was. The bolt was still shiny, used dielectric compound and snugged her up. No Joy. I pulled fuse block, evidently there is no QD on an 86, just the wire harness passes through a rubber boot in the firewall and branches out / connects directly to fuse block. Nothing Exciting I can find.

Ok, while I was wandering aimlessly in the wiring by impulse pulled the Emergency Flasher and they worked! Nothing else. Hmmm

Guess what's left is the ignition switch.

 

[riphip]

Glad you found the problem, will keep this in my problem list.