I have a 1989 sedan deville 4.5 the battery wont stay charged, new batt. alt. had starter checked at auto zone they said it was good,no lights staying on,could it be the ignition switch? Thanks John.

 

what u need to do is buy a digit meter

disconnect the negative battery cable

attach 1 end of the meter lead to the battery and the other end to the wire

if u have a good meter set it to mA

if u have a cheaper one set it to Amp scale
vehicle should have a draw around 25 mA
you may have to put it on the vehicle and let sit for about 20 min to give everything a chance to shut down
do not open doors or turn key (could blow fuse or meter)
one u r going to do is pull fuses out until u reach the 25 mA
take one fuse out see if changes no put back in and continue
what u can do is pull out the fuse for the inside lights that way u can open the door
but u need to make sure this one is not causing the draw
what u r trying to do is find the circuit which is drawing the current
then we can go from there to fix it

 

do what gmtechs said .. we are looking for what many call a 'parasitic battery drain' .. most often, its the power locks or pull downs, but could be something else.



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Had the same problem with my 81. I removed all the ground connections 1 by 1 and wired brushed each one and then put them back on with the dielectric grease. Problem solved. A friend found that it was his door switch on the post that wasn't functioning properly. The interior lites would come on some of the time and others not. good luck.