key trouble

[jerrywmalcolm 21]

starting problems,    long story.    turn key on nothing happens,  put on charger starts right up,  1st,  i have a 69 mach 1 mustang with a  fmx trans.    charge for a day runs great,  store for the nite and it loses charge to 12v,  have to recharge.    had it in a electrical shop he had it for 2 days couldn't find any thing wrong,    maybe someone onthis forum will know something,   o,  have to add,  battery is fine,  no dead cell,  replaced the voltage reg,   thanks   jerry

[69RavenConv 286]

I know you said the battery is good but it sure sounds like battery problems. A spent battery can read 12V at no load but drops off a cliff under load.

The other possibility is a parasitic draw that is draining the battery overnight, like a bare wire touching the chassis somewhere. You could try disconnecting the negative terminal of your battery overnight and see if it starts the next day. Or, if you're handy with electrical measurements, put an ammeter in series with the positive battery cable with the key off and see if any current is flowing. On a stock '69, there should be no draw with the key off, lights off and doors closed (courtesy lights, you know)

Good luck!

[MustangRanch 14]

ditto on parasitic draw - easiest thing to check first...  like raven says. With everything off pull a battery cable - I use negative out of habit but I don't think it matters - put your meter between the cable and the post and see how much draw there is.   At that point, if I see draw, I start pulling fuses to see if the draw stops or not.  That, at least, points me at which wiring to start with.

[Mach1 Driver 560]

19 minutes ago, 69RavenConv said:

On a stock '69, there should be no draw with the key off, lights off and doors closed (courtesy lights, you know)

Well... if the clock still works it will register about a 1.66A hit for around 1/4 sec about every 41 seconds, but other than that there should be nothing. That works out to a constant 0.010A draw- almost nothing. That's a good idea to take the cable off and see what happens. 

[Midlife 814]

2 hours ago, MustangRanch said:

ditto on parasitic draw - easiest thing to check first...  like raven says. With everything off pull a battery cable - I use negative out of habit but I don't think it matters - put your meter between the cable and the post and see how much draw there is.   At that point, if I see draw, I start pulling fuses to see if the draw stops or not.  That, at least, points me at which wiring to start with.

Oh it does matter!  You always want to remove the negative battery cable first.  If you remove the positive cable first, you introduce a chance of slipping the wrench onto the fender, causing a dead short and welding the wrench to the fender and your hand will get very very burned.  Safety first!  Always remove the negative battery cable first.  That is the choice as well for measuring parasitic current draw.