dddead dddeville

[revolcallidac]

Hi, been a while since I've needed to get on here, but my boy's 97 DeVille is acting out. It's left him stranded 3 times now. Battery won't stay charged, it's a new battery. I had it tested this morning for him and it said it was good. Jump car off, starts right up, drive it around, does fine, voltage says 13.8 to 14 on the display. Checked the terminal voltage, watched it climb back up after starting so it's getting juice from the alt. Let it sit for an hour or so, voltage drops quickly. After a few hours, won't start. All those crazy trouble codes come up from having the low battery. Something is draining it down. Trunk light is not on, under hood light isn't on, glove box light not on, interior lights go out like they should. We're stumped and don't want to go uninformed to the dealership without some insight. Once car is started it does great, nothing out of the ordinary. What could be draining it down? I've searched, but found so many different threads about different things. Any insight would be greatly appreciated. It all started just last week. Prior to that, everything was fine.

[JimD]

Sure sounds like at least one bad battery cell to me. New off the shelf failures are not unknown.

[revolcallidac]

That is what I thought too. Would it test out ok even with a bad cell? What about heat? It's been so hot here lately and it first went dead after sitting in a traffic jam outside Knoxville. Stopped for gas, had to be jumped. Then made it home fine. But has happened three times since.

[Cadillac Jim]

Your symptoms sound like a sufated cell to me -- a bad battery. This is the kind of thing that heat or overcharging can do to a battery. Being new is no guarantee that a battery is good. Try a load test of the battery -- any good mechanic, including the dealer, can do a load test.

You've already checked and made sure that the entry and map lights aren't on. It's remotely possible that there is a crack in the battery and acid has formed a path between the terminals. Look for any sign of dampness on or below the battery terminals. I once had a mechanic use an air wrench on a battery terminal and pulled it out from the case; it wasn't obvious and worked fine but it had a bad acid leak.

One thing that you can do yourself to determine whether the battery is draining is to disconnect the battery ground cable. Before you disconnect it, wait a couple of minutes with the engine off to let the computer store all its codes and memory in EEPROM; the FSM says that it takes about 30 seconds. You can then check for battery drain by touching the disconnected ground cable to the battery negative terminal; note that a very small spark is normal. Leave it disonnected for awhile and see if its voltage still goes down. If it does, it isn't the car that's draining it.

Note that batterys give a lot more trouble than Cadillacs, so I'm not really biased here... If the battery stays up when it's disconnected, doesn't have an acid leak, and passes a load test, then post the codes here.

[revolcallidac]

It has been an hour since I posted last...the voltage had dropped down to 10.9. I jumped it off, charged it and did what you said. It's disconnected right now and I'll just wait and see. VOltage at terminals is 12.9 when I disconnected it just now. Thanks for the help so far.

[revolcallidac]

Ok...left battery disconnected for a few hours...voltage didn't drop more than 0.2 Contacts are clean, pos and neg both. Reconnected everything, voltage dropped another 0.1v after reconnection. Cranked, started, and drove car around town...14.0v at first, then 13.7 when warmed up. Came home, backed into carport, shut off. Immediately checked voltage at terminals...9.9 and slowly climbed back up to 10.6 while watching. Came in here to post results. Went back out to check again to see if any higher...up to 10.7v. Why would it drop from 13.7 immediately to 9.9 after stopping? I turned off the twilight sentinel. As I said, AutoZone checked the battery today, and it tested out fine. I wonder if something fried when it was jumped the first time in Knoxville. I'll continue to monitor it through the night. I have a feeling it is something in the car itself. It's been a great car up to last week when this started.

[revolcallidac]

now, an hour later, terminal voltage is 12.8. I didn't try ro start it. will later in the morning. It's built back up on its own.

[revolcallidac]

OK, almost an hour since my last post. Terminal voltage says 12.9. Tried to start car, display says 12.8, turned key, click, no start. Display says 9.9 volts. Turned everything off, terminal voltage says 10.6

What gives? My old truck did this same stuff when my batteries were dying. I'd jump, drive, recharge, park, and then no restart. Replaced both, no probs since. But...if a diode in the alt. is bad, it won't fix with new batt. It just puzzles me, it began as I said above. It worked fine for a few days after that trip, now it's continuous.

[epricedright]

Being the battery is new and under warranty, I would exchange the battery for another new one. If the problem persist, then there must be something still on that is draining the battery. Do you hear anything running like an air pump for your shocks or fuel pump or ?? Does he have an aftermarket stereo power amp that's not being turned off?

[Ranger]

I'd start pulling fuses and checking to see which one has a current draw. Then you'll know which circuit is suspect and can start looking at accessories on that circuit.

[The Fred]

I think you can disconnect your + cable and put a voltmeter between it and the battery + terminal and watch it.. it should show a drain at first and then it should stop... I think

Then you'll know if you have a drain.. I think there is a drain somewhere. Check your trunk pulldown motor (see if it feels warm). That has happened to me a couple of times on Cads - the damned motor back there wasn't making any noise and I finally checked it and it was warm, disconnected it and no more troubles.

Well I replaced it after I was sure it was the problem

[PAUL T]

Did you check your vanity mirror lights. I have seen them drain a battery. Make sure your grounds are good and your wires are not corroded under the insulation.

[BodybyFisher]

Have you taken apart the postitive cable at the battery, there are two wires under the red insulator with a lead lug between them. I would take that apart and look it over closely.. Sometimes there is white and green acid corrosion in there that hurts the connection, clean it good, make sure the bolt does not bottom before it tightens the two cables... The lead lug squashes and the bolt can bottom.

Also, I have seen new batteries with an internal short intermittantly test good and then lose a cell because of a bad internal connection. I would try a known good battery.

[KHE]

I think you can disconnect your + cable and put a voltmeter between it and the battery + terminal and watch it.. it should show a drain at first and then it should stop... I think

Then you'll know if you have a drain.. I think there is a drain somewhere. Check your trunk pulldown motor (see if it feels warm). That has happened to me a couple of times on Cads - the damned motor back there wasn't making any noise and I finally checked it and it was warm, disconnected it and no more troubles.

Well I replaced it after I was sure it was the problem

Fred,

You need to use an ammeter in series with the cable like you describe.

[revolcallidac]

Took battery back and swapped it....so far so good. We'll see what happens.