Intermittent full electrical power outage

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Justin71

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Well it seems the old girl is "powering down" on me occasionally now. Has happened 3x now while driving. At low-speed or idle, but in-gear. Car is C4 auto trans.

Symptom is complete power outage. Engine immediately quits, radio, lights, other internal electrical also go out. In all cases, after a few mins (usually including several shifts of the gear selector trying to get it restarted), everything comes back and behaves normally.

I'm wondering if this could be NSS related? Car is known to have occasional issue where shifter needs to be pushed full fwd to get NSS lockout to allow starting.

Q's:

1) Can NSS this be the issue? Situation occcurs in Drive most frequently

2) What else can cause a fully recoverable power outage like that?

Thanks in advance for some guidance/help here...

Jay

 

Don C

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If wired correctly the NSS provides an electrical path from the ignition switch start position to the "S" terminal on the starter solenoid when the transmission is in neutral or park and that is the only time it has any electricity in it. The backup light section of it has a hot lead connected to it, but only runs to the backup lights when the transmission is in reverse.

You most likely have a loose connection someplace, and I would check the ignition switch and the battery/starter solenoid connections first.

 
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midlife

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If wired correctly the NSS provides an electrical path from the ignition switch start position to the "S" terminal on the starter solenoid when the transmission is in neutral or park and that is the only time it has any electricity in it. The backup light section of it has a hot lead connected to it, but only runs to the backup lights when the transmission is in reverse.

You most likely have a loose connection someplace, and I would check the ignition switch and the battery/starter solenoid connections first.
+1. I'd also closely check the main grounds: battery to engine block, along with the battery post connector.

 

rutkak

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-69 Torino GT, Formal Roof, 351W, Edelbrock 600 cfm, dual plane high rise intake, long tube headers, AOD trans, dual flowmasters, Pertronix II Billet, 3.5 TRACLOC g/r, 15" Magnum 500s, 100A alt, mini-starter
-70 Mach 1, 351W, FMX
Justin,

I think you either have a loose power connection to your ignition coil or you have a short (i.e. 12V hitting a ground) somewhere in your system.

The power connection to the coil is a fun one because it comes from 2 sources depending if you are cranking or running, but that would be my main guess.

Ken

 

Mister 4x4

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I was having similar issues where mine would not want to start and I'd noticed that nothing else seemed to work - then it would randomly start working again for no apparent reason. It never shut itself off when it was running, though, but the accessories would or wouldn't be working.

I solved my issue by insuring the starter solenoid had good ground contact (where the backing plate and bolts meet the apron mounting point). Haven't had an issue since. I also cleaned the contacts on all the cables as well.

 

Justin71

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Thanks for the help guys. No more evidence yet as I keep experimenting. These problems that pop up randomly are slow to troubleshoot!

 

rvrtrash

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I had the same problem with a Mach 1 I had long ago. It turned out I was missing the ground strap between the engine and body (as previously suggested). The electrical system was grounding through the drivetrain, and when I developed a bad u-joint, power would intermittently drop out completely if the internals of the u-joint broke contact. Moral of the story is, check your battery to engine and engine to body grounds, then check your u-joints. ::thumb::

Steve

 

Bill73Ragtop

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former owner (25 yrs) of 1973 Convertible, 351c, A/C, RA
The fact that you lose lights, radio, etc would not point exclusively to this solution, but I had an issue when I first finished my 73 restoration back in '99 where it would quit periodically. After a bit of time it would fire up and everything was normal. The engine would begin to miss, cough, etc and then die out.

After quite a few weeks of frustration I found the culprit to be a reproduction mustard top coil. When it got warmed up to a certain temp, it would die. What threw me was cooler temps would keep it running fine, but once general ambient air temps hit the 50's and 60's ranges it became really obvious. But my lights, radio, etc continued to work since the were on different circuit.

 
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I recently had a very strange problem with my lights & radio going out. Whenever I hit the brakes really hard, lights & radio would go out, but would always come right back on.

Then one day as I was driving, I felt a clunk, like the tranny downshifted real hard. So when I came to a stop sign, the car died. It started right back up, but was running ruff & wouldn't idle. I got the car home & I also noticed that the lights were flickering real bad, like I had an old voltage regulator, but mine is electronic so that shouldn't happen.

So after I checked all the obvious connections, I figured I had to have a short somewhere. I have been having this problem off and on for two years (since I bought the car). I had looked everywhere for a short and never found one.

So anyway this is what happened. The guy who restored my car, never put a grounding strap on from the engine to firewall. Or one anywhere for that matter. I did notice there wasn't one, but this is my first Mustang & thought it was grounded a different way.

And the clunk I heard & felt was the transmission mount failing. Looked like the original trans mount was reused. The car was grounding itself thru the trans mount. So if it moved a bit, like hitting the brakes real hard, it would lose contact, crazy! So after I installed a new trans mount my electrical system was worse, cause now I had no ground.

So all I did was add a grounding strap from engine to firewall & that fixed all of my weird electrical gremlins. I also added one from the front of the engine block to the frame. The new trans mount fixed all the bad vibrations too.

Car is running and driving better than ever now. Sorry for the long story. Hope you get yours figured out!

 
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