oops, lost all electrical power, what did I break?

[MustangNJ]

I was installing a painless aux fuse box, something I have done before.  I had the box wired in, and was getting the 5amp fuse on the box to light up when tested, but none of the other fuses were lighting up with a probe.  somewhere along the line I must have introduced a short.  now with the aux box completely disconnected, there is no electrical power to the ignition or any accessories.  I must have blown something else with a short.  I don't see that there is a main fuse in the box for ignition.  did I blow a fused link or a relay somewhere?  any help would be appreciated.

thanks

 

[MustangNJ]

ok, I'm an idiot. while I was thinking about what to do, I installed the new battery I had recently bought. car starts fine. BUT, I think I introduced a short or something yesterday that was causing the battery to drain overnight. not sure what because the new fuse box was wired main battery AND switched fuse. anyway. back to trying to get the aux box wired in

 

[Don C]

If you're going to do this kind of work on your car you really need a volt-ohm meter. You will then be able to check your battery voltage, check circuits for grounds, trace shorted circuits, etc. You can get one at Harbor Freight for little expense. I have 3 or 4 of them, small and easy to carry around in vehicles, plus a higher quality one for the work bench. I haven't had one fail.

https://www.harborfreight.com/electrical/electrician-s-tools/multimeters-testers/7-function-digital-multimeter-63759.html

 

[MustangNJ]

I have a multimeter, but didn't use it....so my ground tested ok on a probe, but I don't think it was good enough. so I ran the aux fuse box ground to the battery and now its all working as it should. what sucks is the location of the aux box. way up on the firewall, extremely difficult to get in there to screw it down, and now I have to do it a 2nd time....I try to do things like this right the first time because redo's suck....another lesson learned

 

[1sostatic]

Hi 

Residual current drain can be from a service that is normally on the closed side of the key switch is on the wrong side of this switch keeping it turned on continuously.

also a current clamp meter can tell you what residual current is present when your key is off. 

https://www.ebay.com/itm/DT3266L-Clamp-Voltmeter-Ammeter-Multimeter-AC-DC-Resistance-Current-Tester-Meter/223045917555

 

[Don C]

Clamp on ammeters are very useful, you have to make sure you read the descriptions, most won't measure DC current, though.

Another one that used to be popular is inductive ammeters, hard to find now. You can see mine in post #6 of this thread

https://www.7173mustangs.com/thread-dead-battery?pid=214065#pid214065

 

[MustangNJ]

found the issue with car not starting. there is a right angle fitting that connects with a bunch of other wires right above the battery. can someone tell me what this wire is? I now know that the car won't start without it being connected...maybe its old school theft deterrent ?

 

[midlife]

That's not a standard starter solenoid. My guess is (since all of the wires are painted...) is that it is the neutral safety switch line that activates the starter solenoid (should be red/blue wire).

 

[Don C]

That's a later model solenoid. It looks to me like you must have a high-torque starter that has a built-in solenoid, and that solenoid is being used to trigger the solenoid that is on the starter. It looks like the wire on the right-angle terminal is red with a blue stripe, so would be the wire that runs from the ignition switch, and NSS if you have an automatic transmission, to the solenoid and energizes the solenoid when the ignition switch is in the start position.

 

[MustangNJ]

thanks for identifying it. that would explain why the car is completely dead when its disconnected