Complete power shut down

[72stepside]

My father (retired broadcast television engineer) and I upgraded the headlight system on the F100 today by wiring in relays. What a difference!!!

I waited til after dark to get the headlights aimed and went for a test drive. On that test drive, the electrical system in the truck shut down completely. No lights, no ignition, no radio, NOTHING!!!! There was no burnt smell. There was no gradual dimming. It just all shut off right at once. Fortunately I was able to coast down the hill in my neighborhood and go right into my garage.

The fuse hadn't blown at the hot for the new relay system. I took the neg battery cable off just in case. I waited about 30 minutes until Pop could get over here. We put the neg cable back on and all was fine. The truck started right up and all the electrical accessories worked like a champ. We checked the voltages across everything and it all checked out. All the wires are free, not crimped or in a bind. All the new connections are soldered and double shrink wrapped.

It seems to me that nothing we did with the lights should have shut the whole truck down. If anything, just a fuse would have blown if there was a short in that system.

Any ideas?

[spartman]

Sounds like you might have a bad battery cable.

I guess I would check there first.

[kaptnkaos]

Hey 72stepside...

I had exactly the same thing happen to my '68.
That sounds like a bad ground.
Mine was the cable where it connected to the block.
I checked everything.
Like you, I wiggled and removed the cables and the power would come back on...
I kept messing with each time it would go out and finally traced it to the block end of the grounding cable.
I took the cable off and cleaned the end real good and did the same to the block...
I haven't had that problem again...
It could also be the solenoid connection where you hooked up the new harness...
If those connectors were corroded, when you tightened them up they may not be making a good positive connection...

KaptnKA S

[fordman]

now you guys know that you can completely remove the battery while the truck is running. unless the alt is bad or regulator. maybe you guys bumped a loose wire in that system and thats what did it. i am unsure

[basketcase0302]

Chris,

It's those darn intermittent gremlins!
They've been after me for many years now!

It's a good idea to have the voltage meter in the truck for times like this.
I woulda' said you lost the fusible link, (till you said it re-started that easily).
Was it charging over 12.5 volts with the lights on after it re-started?

Jeff

[Banjo]

you say intermittant gremlins joking, but really and truly, that's usually the reason people get project cars/trucks to a certain point and run out of patience and sell for pennies on the dollar. Happens alot. there is NOTHING more frustrating than an intermittant electrical problem. Banjo.

[72stepside]

Chris,

It's those darn intermittent gremlins!
They've been after me for many years now!

It's a good idea to have the voltage meter in the truck for times like this.
I woulda' said you lost the fusible link, (till you said it re-started that easily).
Was it charging over 12.5 volts with the lights on after it re-started?

Jeff

Yep, it was charging over 13 on the restart. That's what has me puzzled. EVERYTHING checked out right correct after it started back up. There was voltage across the battery prior to the restart.

I'm gonna go on a test drive later this morning, with my cell phone in the truck, and see if it happens again.

Chris

[kaptnkaos]

there is NOTHING more frustrating than an intermittant electrical problem. Banjo.

Amen to that Banjo...

Mine did that intermittant thing where I would lose all power just going down the road...
It wouldn't do it for weeks then all of a sudden it would go out again.
I was taking it to pick up an engine stand about 50 miles from here...
It did it about 15 or more times on the road...
That's when I discovered it to be the ground going to the block...
It would lose connection and every electrical system would go out completely. It was driving me nuts until I figured it out...
I was about ready to blow the dang thing up...

KaptnKA S

[basketcase0302]

Chris,
Here's the wiring diagram for the 72, (thank you again Keith).
http://www.fordification.com/images/sch ... _quick.jpg
I'd look closely at the condition of the fusible link wiring on your truck, (in the diagram it's in the upper left).
I'm not sure what the value should be, (as far as resistance measured with an ohm meter). But I'd also check that too.

I've had wiring like this that was broken inside the jacket/insulation. One minute it's showing continuity/next minute it's not.

Also make sure that heavy gauge black wire, (fusible link) is not grounding out on the engine head. Where it connects to the backside of the alternator. And make sure the alternator is grounded to the head/mount good, (although this probably won't be the problem as your 13 volt reading indicated).

Had to change my alternator yesterday. I had forgotten how close the back of the alternator is to the engine head!

Hope this helps.

Jeff

[72stepside]

I drove it around quite a bit today. No problems of course.

I've gone through everything I can think of and all is tight and connected.

Oh well, we'll see.

[fordman]

it was operation shock is all.

[72stepside]

it was operation shock is all.

I think it was just one of those things that happens. There is probably an explanation, it may just remain unknown though. I drove it to work and around town at lunch today with no problem. Who knows...

[uboughtwhat?]

My uncle had a dentside with a 300-6 that would do that. Turned out the ground was loose at the block. Drove us crazy trying to figure it out.

Jeff

[kaptnkaos]

I agree with uboughtwhat?

I'd check the connection at the block...
It might be good and tight, but still not be making a good connection.
I unbolted mine and cleaned the surface real good with some coarse steel wool before putting it back together...
I haven't had the problem since...

Good luck,

KaptnKA S

[Alfred Lord Tenniscourt]

Hey 72, did you get her whipped? I have been hoping you would post again and say that you went over the grounds and the problem stopped...