I have a '98 Chevy Blazer…the battery keeps getting drained somehow.Any body have any ideas as to how to locate the problem? Here are some more details:The first time it happened we replaced the battery with a new one,so that is eliminated!I thought maybe the alternator,but my lights are not dimming and my battery indicator in the dash reads normal all the time.The interior lights do not come on except when I push the button manually.The retained accessory power does not work any more either.We checked all fuses in both panels and everything is good.This happens about once every two weeks or so.Weather doesn’t seem to have any role that we notice.We jump start it and it’s ready to go for awhile.I’m thinking there’s a drain somewhere?And if so,how to pinpoint? I’m hoping to fix this myself as we are living from paycheck to paycheck and can’t afford a mechanic 
Modern cars use power even when they are not running. If it has a security system, that could be a problem, they tend to have problems. Other than that, you need a meter to measure current (not volts) and with the ignition off, watch the meter as you start pulling fuses. See which one(s) have the largest effect on the current and check a wiring diagram to determine what they are feeding. Remember that some drain is normal.
How long does your Blazer sit between uses?
With a GM vehicle of this age, the next thing to check is positive side-mount battery terminal. This terminal has two positive cables going to it that terminate under a red rubber protective cover. It’s under this red rubber cover where corrosion can form causing a connection problem where the engine won’t start. Have both terminal connections removed from the battery, and peel back the red rubber cover to expose the two positive terminals. If a greenish/white powdery substance is found under this cover, that’s what’s probably causing the starting problem. You can try clening this corrsion to establish a good connection. If the terminals are heavily corroded, it’s usually best to replace the positive battery cable itself.
Tester
Weird things can happen. Tom and Ray had a riddle years ago. A car’s battery drained down every night, and the mechanics could find nothing wrong.
The answer was the driveway where it was parked was steep. When they parked it, the automatic under-hood light would come on because of the angle of the hood on that hill. which was steep enough to think the hood was up.
I am not saying your car has an under-hood light. I am just giving you an example of strange things that can happen.
All the posts are good, but if you don’t have an amp meter, you can pull one of the battery cables off, slowly touch it to the battery post. See the spark? Now pull the fuses one at a time and do the same battery cable spark check. WHen you find the fuse that causes the spark to disappear, then you’ve found your circuit to start chasing. What about glove box light? Ash tray light? Keep looking until you find the fuse that make the spark go away. If you have any accessory wires hooked up to your battery, I’d start there.
we use it everday.The most it sits is overnight.It has always happened when my husband goes to leave from work,so it would’ve been sitting about 8 hours.
Here is a link to a site that may help you with this trouble.
thanks.great website!
I’m glad that Cougar kept that Web site url. Here is a simpler little test meter that you plug into each fuse socket to see if that circuit is “live” when it is supposed to be off: http://www.toolsource.com/fuse-buddy-tester-blade-p-98602.html
I’ve seen radiator fan relays turn the radiator fan on HOURS after the engine has been turned off and the engine is cold. It could happen to headlights, also.
After you have parked the car, every so often, go to the car and look and listen for lights and things running. You might discover something that’s coming on, when it shouldn’t.
Do you have the 6-way power drivers seat? Any intermittent problems with the seat or door locks?
There is a wiring harness that chafs on one of the drivers seat mounts and can cause a parasitic draw, like I said usually there are power seat, power door lock symptons.
I have seen both the large wire on the back of the alternator loose and the large cable at the starter solenoid loose
Is there a “work light” on the underside of the engine hood? Is it staying on?
The OEM radio can also be the source of a excessive draw
Check the vanity (illuminated) sun visors I have seen these pull close to 1 amp each
just disconnect them (sometimes the wiring is pinched under the base)
if you say the RAP (retained assy power) module is inop,unplug it and see if that helps.just because the features do not work does not mean the module is dead,only means its not capable of outputs,but could still be alive at times.
just a thought.