70 RT, electrical system dead from one moment to the next

[Padawan]

Hey guys! This just happened to me and being the noob I am I'm totally perplexed by what could cause this:

Wanted to pull back the car 3-4 feet to replace a bulb, so I start the engine, put it in reverse, pull back a little and the engine dies. Well, didn't let her warm up, no big deal, turn the key again, nothing, remember to put it back in park, turn the key again and -- nothing. And now it's just all dead, not only does the starter not move, I don't get any lights, not even hazard lights or lights in the glove compartment. I know the battery is not the best, but it still did its job and when I bridge the contacts with my primitive circuit tester, the indicator light glows. Crawled under the dash and there is a huge mess with a lot of disconnected ends (most probably because I pulled out my radio a few months back).

What happened? 

[Chryco Psycho]

start checking the main connections , battery cables , bulkhead connector plugs , plugs that feed the steering column also check the fusable link near the start relay

[Giveitawack]

A friend of mine has a sixties Barracuda. His car just died on the road. No power to anything. I helped him push it off the road.
He later found out that it was the ground cable. The crimp on connector attached to engine/body. Probably corrosion.

[JayBee]

My guess - battery. Had enough juice to start the car one last time then went totally dead. I had to replace my battery last month. Left a car show and it started fine for the drive home, next morning - nothing.

[jackie]

Did you try to start it in netural? After that begin at the battery. A test light and a volt meter is a must have tools. Put the test light on the battery. Get someone else to hit the switch, see if the light goes out, or dim's..You can see if your switch work's..Old cars you have to clean and check everything..All parts go bad ,but so many times it's just bad connections..

[Jesus H Chrysler]

  Many many times I've gone to start old cars and get "the click".  I twist both battery terminals and it fires right up.  One minute you have just enough connection to work, the next the corrosion takes over and blocks you.  Go through the main connections and try to jump the starter solenoid.  That will let you know if the main components are functioning.

[Padawan]

Thanks for all the tips! I just cleaned both battery terminals and the ground cable connection to the block, still nothing. Interestingly, I only have a ground to the engine, none to the body... anyway, the battery seems fine, test light glows quite bright and steady when connecting the terminals. When I tried the cables at the starter relay I must have short-circuited something as there were quite some sparks and I heard the starter for a split second. Could it just be the starter relay? Would that also explain why there is no light, not even in the glove compartment (overhead light never worked)? 

[MEK-Dangerfield]

The starter relay can fail on you, but that doesn't explain the lack of interior lights.

How new are the cables on the battery? My radar is telling me something is loose or you have an old cable that has deteriorated. You can't always tell by looking at it.

[Chryco Psycho]

the ground cable should have a pigtail out to the headlight ground on the rad support . Sounds like a bad start relay to me . You must have other issues with power to the headlight switch / dimmer etc

[Padawan]

How new are the cables on the battery? My radar is telling me something is loose or you have an old cable that has deteriorated. You can't always tell by looking at it.

I have a mixture of very old and recently renewed cables since the alternator was replaced back in February. It must be something very basic since everything is failing, but if it was the battery I should at least see some faint light somewhere. Maybe I'll still test to bridge the battery, see if power is back when the alternator is running, or start tracing every single cable... 

[BS CUDA]

the ground cable should have a pigtail out to the headlight ground on the rad support . Sounds like a bad start relay to me . You must have other issues with power to the headlight switch / dimmer etc

 Not more than 1 hour ago I was out in the garage trying to fire the car after tidying up some wiring. Turned the key and nothing, zero, zilch  no headlights no nothing. I have a goofy 3 prong plug on the starter relay that only 1 prong of it hooks to the relay. Why the other 2 prongs - I don't know - believe it had something to do with the MSD install etc. Anyhow after scratching my head awhile I started moving the goofy plug to the other positions and BAM it fired. So yes a faulty or improperly installed relay can indeed create a lot of havoc including lights. At least in my case as the car is running great again. 

[Padawan]

the ground cable should have a pigtail out to the headlight ground on the rad support . Sounds like a bad start relay to me . You must have other issues with power to the headlight switch / dimmer etc

Mine really is only a thick cable from the battery to the block, strange. I haven't had issues with the lights before, other than a non-working front right parking light (turn signal worked, though). All wires except the ones to the alternator seem to still be the original ones, I guess it's time for them to be replaced.

Nice, BS CUDA, that means for 50% of us the car is running again. That's something! 

[Giveitawack]

You could try a jump start cable to ground. Clamp it on the battery minus and the body, block etc. That should rule out the battery cables.

[Super Blue 72]

   How have you been!  Haven't heard from you in a while!

My car had similar issues, started right up then next time I wanted to start it-absolutely nothing, and of course it was was when I moved it to the end of the driveway so it was blocking all the other cars in. 

Turns out it was an aftermarket clamp on the positive cable, not a 1 piece deal.

Try having someone sit in the car and turn the key to start and then start jiggling wires under the hood starting at the battery terminals, try twisting the clamps first, then move check the pigtail at the radiator support then move down the positive wire.

Since you have no power at all, no lights, you can do this by yourself if you keep the headlight switch on and see where you might have a loose connection when the lights turn on.

I'll try to give you a call.

[Padawan]

This thing is haunted!

- Battery is fine, still at 12.7V, green light
- Grounding the battery against the frame, additionally to the engine block, doesn't help (the pigtail to the radiator support seems to have been cut a long time ago)
- Thought I found the culprit at the middle bulkhead disconnect. That stuff seems to still be original, cleaned it up a little and put it back, still no luck

Last guess is the fusible link is blown as Chryco suggested, going to check that next, could it explain a no-power situation or only a no-starting situation?