Our 93 LT1 (with under 7,000 miles) obviously sits a fair amount of time. It usually sits 2-3 weeks at a time and is only driven on nice days. But, after sitting 3 weeks, the Optima Red-Top battery is dead.
Today we charged it, and upon re-connecting the battery cables, the alarm went off, the underhood fan turned on, the heater turned on, and the hatch popped (the keys were nowhere near the vehicle during this either).

We had an issue with the computer, and the local GM dealer replaced it. Though i'm wondering if this computer is also defective at all, as the above all occured while re-connecting the car's power. Additionally, when disconnecting the cables to charge the battery, as the negative was coming off (first), as it arced while loosining the post, the interior chime dinged a couple times and a couple random indicator lights on the dash flashed (again, key was nowhere near the car at the time...and DEFINATELY not in the ignition).

What do you guys think is going on? When charged, the car pulls really strong and smooth and has the power it should, but it DOES lose charge relatively quick (volts gauge will read high even if the car sits 1-2 weeks and is then started), and the battery is new and was fully charged upon install.

Look forward to your replies, and thanks for reading my post!
-Blue93LT1 :

 

Sounds as though you have a circuit (or circuits) open somewhere. There should be very little arcing when you pull one of the cables off the battery. Because of all the processors that are always drawing power, you should see just a tiny arc as the cable is pulled. The

You need to measure current draw at the positive battery cable. Install an amp meter between the positive cable and battery post to see what amerage draw there is.

Then you can pull fuses one at a time to see if the draw drops down and that will give you an idea on what circuit to look at. A wiring diagram will really be needed here. There is a complete electrical diagnosis section and wiring diagrams for every circuit in the factory service manuals so get a set from Helm ( www.helminc.com ) if you don't have them.

The battery should easily retain a charge over three weeks to be able to start the car. I have left my 92 sit for over two months with no battery tender hooked up and it always cranked up within a couple turns.

With the ignition on before starting you should see 12 to 12.4 volts on the digital dispaly. Once the engine starts, 14-15 volts is normal until the alternator refreshes the battery and voltage should drop to 13.8 to 14.2 or so depending on what you have turned on. Less than 12 volts on the display is usually indicative of a weak battery.

I have read some posts that mentioned that there may be some Red Top batteries that will fail after only 2-3 years. Probably a bad batch.

Did you have the ECM or the CCM replaced?? Or both? Engine fans are controlled by the ECM and it sends a grounding signal to the cooling fan relays to cause them to start. Hard to say about the alarm and harch release. Both depend on signals to ground their respective relays and those signal may very well come from the CCM.

 

ECM was replaced (the main computer right above the brake/clutch resovoirs). What/where is the CCM? Don't think that it was replaced at the same time. (The problem causing the ECM to be replaced was that the car would intermittently just cut out during driving, then turn back on fine-a split-second lapse of power, like turning the key off/on real quick going down the road. It would then flash all the dash lights, and do other freaky things).
Yeah something's pulling power. I'll have to break out the multimeter and figure out what's going on. I know the alt. charges the battery just fine and it puts out normal voltage running, but something keeps draining the battery. Also this the reason for getting an Optima - the Delco replacements we purchased drained, so we figured the Optima would hold longer. Obviously it's something decent draining the battery over only a couple of weeks.

Any recommendations on where to start? I'm not the most electrical-savvy person, but can perform pretty involved tasks (albeit being "walked" through them). When you say to hook an amp meter between the + cable and battery post...do you mean w/the cable off the battery, using the amp-meter as, essentially, a "jumper" to complete the circuit? Would a standard Multimeter be able to handle the job, or would I need more specialized/heavy-duty tools to do so?
Thanks though for the help so far,

Mark

 

First check at night for the underhood lights, vanity mirror lights, map compartment light. Also, do you have a radar detector, aftermarket alarm, or aftermarket audio? check em.
GM says the leakage current should not exceed 50 milliamps. My 87 draws 27 ma. Yes, you can place a multimeter set to amps in series with the negative battery terminal to the battery cable, this will allow you to measure current. Start the meter out on its highest range because the courtesy lights will come on and they draw 3-5 amps. You can damage your multimeter if you have it set to say 100 ma. full scale and then connect it up; 3 amps will damage the meter. Pull the fuse for the courtesy lights because the passenger door needs to stay open while you pull a fuse at a time and watch the milliammeter to see if you have a dramatic drop in current. If you do, then that circuit needs to be examined more closely to see what is drawing current. If no luck with the fuses, check the fuse block next to the battery (I think 93's have one) the same way.

 

jfb,
Thank you for the info. I knew multimeters can't handle large loads, didn't know how much. Glad to hear it 'should' be fine for this test though. We're going to install a quick-disconnect for the ground cable no matter what (as the car sits a fair share of the time), but I will still examine the draw, probably this weekend.
The car has no aftermarket anything - it's bone stock. The keyless system was also disabled prior to parking the car last. It re-enabled itself upon charging/reconnecting the battery (don't know if this is default procedure or not). But something's still up as a bunch of stuff like the fans/heater all came on w/o the key. Will investigate and keep posted.
Thanks,
Blue93LT1

 

Almost all of the cockpit electronics get power through the ignition switch, so I recommend that you check the switch itself which is activated by a rod from the ignition tumbler. The switch mounting might be loose and the rod won't turn the switch off reliably.

 

I bought a red top for my C5 in April replaced it last week it had gone bad. I use a battery tender on it also.

 

Well i'm going to be checking the voltage/amperage today. Here is my multimeter - this will indeed handle the load?
http://www.sears.com/sr/javasr/produ...00&tab=des#tab

Also, when I'm connecting the probes to the battery and terminal, will the multimeter act as a jumper and actually connect power to the vehicle, or will the multimeter read voltage but not pass the current to the car? The reason I'm asking is that like I mentioned before, some random high-load items (underhood fan, horn, etc) occasionally run for a second or two at battery-reconnect, and I don't want this completely frying my multimeter (as cheap as it is)

Plus, I don't think it's ignition-switch related. The car shuts off entirely, and nothing in the interior gets power with the key out of the ignition (except for when dis-and-re-connecting the battery). Thus I'm thinking a circuit is shorted/loading somewhere/somehow. Nothing on the car controls the fans, heater, door chime, dash lights, and alarm all together, does it (CCM/ECM/etc)? Isn't a combination of them that controls the problematic items I've mentioned?

Hopefully I can get this narrowed down today w/o frying anything. Obviously i'm not the MOST electrical-savvy, but I know enough of what to do, as long as I get my answer(s) from the above.

Thanks for the help/ideas so far!