Eletrical Problem, question 289 v8

jboggess

jboggess

Senior Member
Hey all. Crazy question. So i recently restored a 65 Ford Mustang, with a 289 V8. And i have a problem. When the engine is off, and the key is out, and when there is nothing eletrical running on the car, the battery dies over night. Now when i undo the battery cables and leave them off over night the battery stays charged. And when the motor is running, the battery tests good for being charged. So any idea? Maybe a short? :confused: Thanks for your help.
 
Do you have a stereo radio fitted to the car. These things if you have electronic tuning they have a continual feed to retain the tuning memory. I have seen some of these draw 1/4 amp but they won't drain a battery overnight. Is your trunk or dome light staying on. These can easily flatten a battery. An old battery will not hold the same level of charge as a new one.
Regards
 
Further to my earlier post, if you have a multimeter, turn the ignition off and remove the key. Disconnect the battery lead and connect the multimeter across the lead and the battery terminal. If you have a discharge, with your multimeter on the 10amp setting, you should get a reading of some sort.
This will give you somewhere to start.
Regards
 
Sorry, so i put the meter cable on the postive battery termal then where do i put the other one? Thank you for your help! :confused:
 
So i take the postive cable off the battery and put the meter on that one? Then the other one on the negative termal battery?
 
let the engine cool down for several hours with the hood up, put your hand on the alt or gen or the regulator, if any of them are warm you now know where to start, or you can take the battery cable off the ground side batt and hook a multi meter to the batt and the cable, if you have a circuit thats drawing juice it will show at the meter, now start pulling fuses one at a time till you find the one thats causing the drain, find out what it goes to and check there
 
My Father-in-law had the same problem with his 66 Mustang. We found a short in his left side blinker. Check all your connections to make sure nothing is grounded out.
 
Sorry I never got back to you sooner, we have a 10 hour time difference
Hook the multimeter up as already suggested, with +ve lead to +ve battery terminal and the -ve lead to the lead you have removed. Make sure your multimeter has a 10 amp testing function. If it has a lower rating you may damage the meter.
Does your generator light come on and off when ignition is on?
It is possible if you are using a Chev alternator for you to have the connections reversed which will flatten the battery, but you say you have a separate regulator.
Are you using a generator or alternator?
Keep us posted.
 
Well I'm using a alternator, and I double checked the wires and they are all hooked up right. But the alternator gets hot. What does it mean? Thanks again
 
jboggess said:
Well I'm using a alternator, and I double checked the wires and they are all hooked up right. But the alternator gets hot. What does it mean? Thanks again
Click to expand...

I would have the alternator checked out. If the drain is as severe as you say it is, its probably a bad diode in the alternator.

Disconnect the alternator, charge the battery, and put the battery terminals on (alt still disconnected). If the battery stays charged over night, the alternator is the culprit.

Another way to test - try a jumper with another battery. If you get a lot of sparks connecting its probably the alternator.
 
Alt will usually ground through the alt case. Battery ground is usually on the engine on that car so it should be well grounded already. My guess would have been the diode also.

Most parts stores will test for free.
 
Had a similar problem,the new alternator had a bad stator.Take it to an automotive electrical shop for testing Autozones tester showed good when it was defective.
 
Well folks i found out that in the new wire loom i installed, that the wire connnections what goes from the starter relay to the alternator is not makeing contact somewhere inside the loom. So i guess i am going to undo the loom and see if i can find where its not makeing a connection, and see what happens. Ill keep ya posted. Thanks
 
If your battery is going dead overnight when hooked up but not when it's unhooked then you have a draw. Unhook your neg cable and connect your tester between the post and the cable, if it lights up then there is a draw (open circut) somewhere. To help isolate the draw have someone remove the fuses one at a time, while you watch the tester, when the light goes out you will know which circut it's in.
 
If you remove the batt wire on alt,and if you have a I IGN wire on regulater disconnect them , that may end short.
It would be easyer to use light bulb between pos and cable.
 
You must log in or register to reply here.
Back
Top