pictures... of the alternator from several angles so we might be able to identify it and see which wiring..
and a huge warning..
i have only been a mechanic for 35 years.. and i do a ton of electrical work on cars ..
if you have a battery cut off switch... its designed to CUT off the battery.. NOT kill the motor ..
if the battery disconnect switch is turned off... while the engine is running. there is a chance of serious damage to the alternator components..
when the battery cut off switch contacts are disconnected.. there is a huge loss of load on the alternator output. the alternator was creating electrons at 14.6 volts or so.. the instant the switch is opened.. the electrons being created in the alternator build up as there is no place for them to go.. the build up becomes a voltage spike as the regulator takes a few hundredths of a second to turn off the power to the rotor windings. its really easy if the alternator is putting out any were above 30% of rated output at the time the switch was opened for the voltage spike to go over 100 volts for that split second..
diodes in many alternator are rated at 25 or 35 amps 100 Volts PIV.. peak inverse volts.. if you exceed the voltage you can fry the diodes. causing them to blow out and open.. or what is worse... is when they short out.. they will flow current in both directions... a diode is a one way check valve..
perhaps this is what you are finding..
do you own a hand held digital volt meter.. this is a link to a voltage drop test i use to verify the electrical connections are working properly.. print this.. it will not only help find issues on hot rods but on everyday drivers including the latest computerized cars..
voltage drop test link.. http://i.imgur.com/WMDprhm.jpg
since you have a rear mounted battery.. you will need a probably a jumper cable laid on the floor under the car to extend the reach of the volt meter test leads..
this is the meter i use to perform these tests.. Digital Multimeter - Save on this AC/DC Digital Multimeter the really cheep under 10 buck meters may not be accurate at these tiny fractions of a volt you are checking for.. i know that as i have tried them..
let me walk you thru the tests....
engine off.. turn on the headlights for one minute .. then shut them off and check the voltage ... if the battery voltage is less than 12.50. volts.. then you need to recharge the battery slightly.. the reduced charge will throw the test results off ... you can still do the six steps.
start the engine.. turn on the headlights to create a mid sized load on the electrical system.
test 1... should be over 14.1. and usually less than 14.8 volts.. if the alternator is not putting out current above the battery voltage the test results will be off..
test 2 requires with rear mounted battery that you hook up the single jumper cable to the negative battery post.. so you can connect the one of the volt meter test leads to the other end... touch the engine block.. i would love to see 0.04 volts.. please post results.. by number... this checks the engine blocks negative connection to the battery.. 0.04 is 4/100ths of a volt.
test 3 also requires the use of the single jumper cable or just connecting between the negative battery post and the body.. less than 0.02 volts would be a great result.. this checks the negative connection to the body.. since all the lights and many other devices are connected to the negative thru the body this is an important test.. 0.02 volts is 2/100ths of a volt..
test 4 can be done up front.. engine block to the firewall . or body... 0.02 volts again is a good result. why.. the alternator puts out almost 2 volts more than the battery.. with most of the electrical devices grounded to the body.. failure to have usually a braided ground strap from the engine to the firewall or body will really effect how the electrical system works.. as much of the load is on the alternator with the engine running. electrons like to take the shortest path..
test 5 is hard to do on some cars.. its designed for cars with underhood fuse boxes... if your car is equipped with a terminal block where the wiring from the alternator or from the positive battery connection supplies the rest of the electrical system with positive power this is the test to perform.
test 6 is really important.. with a rear mounted battery.. you will really want to be careful.. as i am going to have you use the single jumper cable laying on the floor under the car and clamping the end to the positive battery terminal.. clip one lead of the volt meter to the clamp on the floor.. do not let the jumper cable touch the car.. hopefully your test leads are long enough to do this.. and touch the other test lead to the alternator output.. this reading is going to be in most cases... around 0.3 volts. less is better. some cars like 60s and 70s mopars will have 0.7 volts as the length of the wire between the alternator and the battery positive is really crazy long.
on a conventional car.. i can perform the first 4 steps in under a minute to check the negative side connections..
testing the positive side is not always possible.. as some cars you cannot get to the back of the alternator to touch the threaded stud.. not the ring terminal in most cases..
why are these small fractions of a volt a good result..
if you have a poor electrical connection.. this test may find it.. its just the beginning test and actually the last test i perform on any car before i close the hood to verify that the electrical system is properly hooked up.. i hate comebacks..
the 4/100 or 2/100 of a volt results is the actual resistance of the copper wire to electron flow.. if your tests show more... you will want to narrow the test locations .. to identify the poor connection..
if you have a daily driver that has an underhood fuse box.. most cars 1994 and up have them.. spend a few minutes with your digital volt meter and the paper copies of the voltage drop i posted above and perform it so you can see what the results may be..
you said the car has a short... this is the first step in any proper electrical diagnosis..
try to post results by number..
percentage of battery charge 12.65/12.45/12.25
1....______
2....______
3....______
4....______
5....______
6....______
lastly.. with a battery cut off switch.. you will want to perform a voltage drop test from both of the threaded studs individually to the negative battery post.. this is done engine running and the headlights on..
this does not explain why the alternator seems to be drawing current with the engine off.. but you have not described the type of charging system.
sorry for the wall of text.. just trying to help.. use the printed voltage drop test.. at the car.. most of this was explaining the need to modify the procedures for checking with rear mounted battery..
and a huge warning..
i have only been a mechanic for 35 years.. and i do a ton of electrical work on cars ..
if you have a battery cut off switch... its designed to CUT off the battery.. NOT kill the motor ..
if the battery disconnect switch is turned off... while the engine is running. there is a chance of serious damage to the alternator components..
when the battery cut off switch contacts are disconnected.. there is a huge loss of load on the alternator output. the alternator was creating electrons at 14.6 volts or so.. the instant the switch is opened.. the electrons being created in the alternator build up as there is no place for them to go.. the build up becomes a voltage spike as the regulator takes a few hundredths of a second to turn off the power to the rotor windings. its really easy if the alternator is putting out any were above 30% of rated output at the time the switch was opened for the voltage spike to go over 100 volts for that split second..
diodes in many alternator are rated at 25 or 35 amps 100 Volts PIV.. peak inverse volts.. if you exceed the voltage you can fry the diodes. causing them to blow out and open.. or what is worse... is when they short out.. they will flow current in both directions... a diode is a one way check valve..
perhaps this is what you are finding..
do you own a hand held digital volt meter.. this is a link to a voltage drop test i use to verify the electrical connections are working properly.. print this.. it will not only help find issues on hot rods but on everyday drivers including the latest computerized cars..
voltage drop test link.. http://i.imgur.com/WMDprhm.jpg
since you have a rear mounted battery.. you will need a probably a jumper cable laid on the floor under the car to extend the reach of the volt meter test leads..
this is the meter i use to perform these tests.. Digital Multimeter - Save on this AC/DC Digital Multimeter the really cheep under 10 buck meters may not be accurate at these tiny fractions of a volt you are checking for.. i know that as i have tried them..
let me walk you thru the tests....
engine off.. turn on the headlights for one minute .. then shut them off and check the voltage ... if the battery voltage is less than 12.50. volts.. then you need to recharge the battery slightly.. the reduced charge will throw the test results off ... you can still do the six steps.
start the engine.. turn on the headlights to create a mid sized load on the electrical system.
test 1... should be over 14.1. and usually less than 14.8 volts.. if the alternator is not putting out current above the battery voltage the test results will be off..
test 2 requires with rear mounted battery that you hook up the single jumper cable to the negative battery post.. so you can connect the one of the volt meter test leads to the other end... touch the engine block.. i would love to see 0.04 volts.. please post results.. by number... this checks the engine blocks negative connection to the battery.. 0.04 is 4/100ths of a volt.
test 3 also requires the use of the single jumper cable or just connecting between the negative battery post and the body.. less than 0.02 volts would be a great result.. this checks the negative connection to the body.. since all the lights and many other devices are connected to the negative thru the body this is an important test.. 0.02 volts is 2/100ths of a volt..
test 4 can be done up front.. engine block to the firewall . or body... 0.02 volts again is a good result. why.. the alternator puts out almost 2 volts more than the battery.. with most of the electrical devices grounded to the body.. failure to have usually a braided ground strap from the engine to the firewall or body will really effect how the electrical system works.. as much of the load is on the alternator with the engine running. electrons like to take the shortest path..
test 5 is hard to do on some cars.. its designed for cars with underhood fuse boxes... if your car is equipped with a terminal block where the wiring from the alternator or from the positive battery connection supplies the rest of the electrical system with positive power this is the test to perform.
test 6 is really important.. with a rear mounted battery.. you will really want to be careful.. as i am going to have you use the single jumper cable laying on the floor under the car and clamping the end to the positive battery terminal.. clip one lead of the volt meter to the clamp on the floor.. do not let the jumper cable touch the car.. hopefully your test leads are long enough to do this.. and touch the other test lead to the alternator output.. this reading is going to be in most cases... around 0.3 volts. less is better. some cars like 60s and 70s mopars will have 0.7 volts as the length of the wire between the alternator and the battery positive is really crazy long.
on a conventional car.. i can perform the first 4 steps in under a minute to check the negative side connections..
testing the positive side is not always possible.. as some cars you cannot get to the back of the alternator to touch the threaded stud.. not the ring terminal in most cases..
why are these small fractions of a volt a good result..
if you have a poor electrical connection.. this test may find it.. its just the beginning test and actually the last test i perform on any car before i close the hood to verify that the electrical system is properly hooked up.. i hate comebacks..
the 4/100 or 2/100 of a volt results is the actual resistance of the copper wire to electron flow.. if your tests show more... you will want to narrow the test locations .. to identify the poor connection..
if you have a daily driver that has an underhood fuse box.. most cars 1994 and up have them.. spend a few minutes with your digital volt meter and the paper copies of the voltage drop i posted above and perform it so you can see what the results may be..
you said the car has a short... this is the first step in any proper electrical diagnosis..
try to post results by number..
percentage of battery charge 12.65/12.45/12.25
1....______
2....______
3....______
4....______
5....______
6....______
lastly.. with a battery cut off switch.. you will want to perform a voltage drop test from both of the threaded studs individually to the negative battery post.. this is done engine running and the headlights on..
this does not explain why the alternator seems to be drawing current with the engine off.. but you have not described the type of charging system.
sorry for the wall of text.. just trying to help.. use the printed voltage drop test.. at the car.. most of this was explaining the need to modify the procedures for checking with rear mounted battery..
