'66 Mustang Wiring issue / battery drains

[stangman16]

I think I've got a short somewhere in my wiring and I really got to get this fixed here within a two month time span. I'm definitely not a pro when it comes to wiring, so any help would greatly be appreciated. My battery drains real easy, I have to charge it every time I want to try and start the engine.

I've seen before where someone recommend disconnecting the negative to the battery and hooking up a test light. Where do you hook the wire clip of the test light to, and also where do you touch the screw-driver part at? Do you clip that on the negative cable and touch the (-) post on the battery? (I have side-terminals BTW) Once I get this figured out, I then disconnect the few fuses that I have one by one to determine which circuit the short is on and proceed looking at the wiring from there?

 

[pabear89]

Disconnect the neg cable......Attach the clip of the testlight to the neg batt post and then connect the probe end to the cable.

If the Light is on you have a Drain.

Start by removing the fuses till it goes out.
That last fuse you pulled out is the curcuit that is draining your batt.


PB

 

[TOM B]

Could be a diode in the alt to

 

[stangman16]

well... I'd love to change the alt. as soon as I can, I'm going EFI on this thing, got 85% of the parts, just need fuel pumps and engine gaskets basically. (and a new alt.) Would you believe this car has a GM alt in it!? I'm thinking I should go the 3G style, but I don't like the fact that if the voltage drops on the battery below a specific point, it stops charging... or so I've been told. Can anyone enlighten me with this - or has anyone done this swap that can share some details?

 

[Ronstang]

Could be a diode in the alt to

That was going to be my guess also as it is one of the only ways to drain a battery without it being obvious. I have seen this problem on several occasions in older cars. My Shelby suffered from this exact problem about 10 years ago. It drove me crazy as to why the battery would go dead in a day or two until I thought about it. The spark created by simply removing and touching the ground cable to the battery was hefty and the alternator was the only thing that made sense. A quick trip to the local auto parts store confirmed a bad diode. I simply bought the parts at the alternator/starter rebuilder in my area and fixed my unit.