I hate to say it but if you toasted the wires to the Amp meter you likely damaged other wiring in the engine harness and dash harness.  One AMP wire comes from the alternator and the other comes from the battery side of the solenoid.  Together they form a "shunt" across the heavy wire from the alternator to the battery and provide a representation of what's happening between the alt. and the battery. 
Reversing the wires will only cause the AMP meter to indicate backwards but will not cause any other trouble.  Since both wires are connected directly to the battery...without any fuse protection...they will get very hot, very quickly if shorted to ground, and that's what I suspect you have somehow done.

At this point I recommend you disconnect the Amp meter wires at the alternator and at the solenoid.  That will remove the battery source.  Then remove the cluster and try to find out what you have touching ground...Amp meter, I suspect. 

And then, you need to determine if the harnesses are beyond repair.  If you are good with an Ohm meter and have the time, you can disconnect everything and test wire to wire to see if any two wires are connected together when they shouldn't be.  If you go this route be sure to unplug the engine harness at the firewall and test each harness separately. 

Or...you can disconnect the Amp meter as stated above, find the short and fix that, then connect battery power through a jumper and a 5 amp in-line fuse.  If the fuse blows you need to do more looking.  If it doesn't, change to a 25 amp fuse and test-run various stuff...but not the starter as 25 amps won't handle that. 

If it doesn't blow the fuse and everything works the Mustang Gods have smiled on you.  If not then you will either need to replace the harnesses or open them up and make required repairs. 

As for the fuel gauge, you just put in a new sender so that would be the first place to check.  Once you get things powered up again, disconnect the wire to the sender and ground it.  The gauge should go to full.  If not the gauge is bad or the wire between the gauge and sender is open.  If the gauge does go to full, the new sender is bad...big surprise.

Good luck.

BB
 

Last edited by Bullet Bob (3/28/2016 8:17 AM)

skunkape wrote:

bad news and good news. Bad news, the wiring harness from the gauges to the firewall is fried. Also the harness from the firewall to the battery. Good news, Mommy wants to go for a ride very soon so she gave me the okay to order a new harness. should be here by this weekend.

I think you'll be glad you went that route.  Shaky wiring is going to leave you high and dry...or worse.  This is one more place where, "Do it once, do it right" really are words to live by. 

You know, it's very easy to add a nice, neat Middy Fuse holder with a, say 40 Amp fuse to the  "always hot" circuit into the cabin.  Then this will never happen again.

Good luck.

BB

Last edited by Bullet Bob (3/28/2016 10:56 AM)

  Hey BB, would the small gauge existing wiring act as a fusible link before the 40 amp fuse blows?
 

Last edited by Rudi (3/28/2016 5:55 PM)

Well that's what he gets for smoking...

You could use a self-reclosing circuit breaker that would reset itself after the extra load was removed.

http://www.oreillyauto.com/site/c/detail/MRY0/35873/N0227.oap?ck=Search_circuit+breaker_-1_2119&keyword=circuit+breaker

Bullet Bob wrote:

TKOPerformance wrote:

Well that's what he gets for smoking...

Okay...but does he really deserve to get rear-ended on the freeway on account of loosing his lights?
 

No, but the adage goes "smoking kills".  Its always assumed that its due to health risks..

I realize sarcasm doesn't come through in this stuff very well, so to be clear: I'm #$%&ing around. 

skunkape wrote:

Michael, Is this circuit breaker installed between the voltage regulator and the wiring to the firewall?

You could install one anywhere you were concerned about too much load (or a hot wire shorting out) burning up your wiring.

Ford used a circuit breaker like this to protect the wiring harness when adding GT foglights.
One installation note though... The base may have to be screwed down to a grounded surface for it to work properly... not sure.
 

whlnut wrote:

BB, which is the "always hot" wire to the cabin on a '66? Thx

Sorry for the delay...this one got away from me.  The always hot for ignition and accessories in a 66 is the black w/yellow trace (#37) that runs from the solenoid to the main firewall connector and then to the ign switch as #21, yellow, then to the headlight switch as #25, black with orange trace, and then to the fuse panel as #37.  This is the one you could use a fuse on right near the solenoid.

There are also red and yellow wires that go to the Ammeter and these are also hot all the time which, I suspect, is why Skunkape had his troubles.  You could also fuse these near the alternator and at the solenoid, with a small 10 or 15 amp fuse.  They only carry a small portion of the total vehicle load and if the got in trouble an popped a fuse it wouldn't have any ill effect on the vehicle. 
If you elect to do this, I would recommend an in-line fuse just after the yellow wire leaves the heavy Black-yellow running from the alt. to the solenoid.  The red wire from the solenoid to the ammeter could be fused at the solenoid. 

BB

 

Last edited by Bullet Bob (3/30/2016 8:30 PM)