Battery Discharged Overnight?

[Gardd]

My Taurus (1999 SE Wagon / Duratec) was just fine & dandy yesterday while getting groceries & running errands.

I wanted to pop out to the store this afternoon and it wouldn't start - the battery is too low to crank the engine. I've taken the battery out and hooked it up to a charger. The battery is new(ish), bought last November.

What could have caused an overnight discharge like this? The car hasn't had any electrical problems whatsoever before, and I'm pretty sure nothing was left on overnight.

It's been really rainy for the past few days with a lot of sudden heavy downpours, and late yesterday through the evening the humidity was 100%. Like a steambath, very uncomfortable.

I might be barking up the wrong tree but could the moisture & humidity have caused a short or something?

[danielsatur]

If the battery terminals were dirty or loose, the alternator couldn't charge the battery good.

[shorod]

Do you have a multimeter and understand how the basic functions on it works? To offer much help, we're going to need to start with some voltage measurements with on the battery terminals with the engine off, on the battery cables with the engine off, and at each of these locations when the engine is running. If you're unable to get the engine started, then knowing what the battery voltage drops to when the starter is engaged at each of these locations will be important as well.

-Rod

[Gardd]

Thanks, I don't have any experience with that kind of thing but I have a buddy who'll be willing to help with multimeter measurements. Probably tomorrow (if he's not out golfing ) - and besides I think the battery won't be fully recharged until late this evening.

Thinking back over the past while - I had the transmission cooler lines replaced last week and when I took the battery out today I noticed that the mechanic had installed a new connector on the negative battery line, and he put a lot of protector gunk on the cleaned terminals. Red on positive, blue on negative.

I didn't ask for a new connector when the transmission lines were replaced so I guess the mechanic noticed I needed a new one and threw it in as a freebie. I wonder if this has something to do with today's surprise. But the new connector isn't loose or anything; he did a good job with it and it's solid.

Anyway I'll post again as soon as I can get multimeter measurements.

Thanks again!

[Gardd]

Well, my friend's going waaay out of town on a golf trip today so I'll try to get a digital multimeter at lunchtime and I'll test the battery as soon as I get home late this afternoon. Probably high time for me to get a multimeter and learn how to use it anyway.

[Gardd]

Multimeter's a nifty little thing. I'm glad I bought it. I'll probably be testing everything with reach for a while and driving everyone around me nuts.

Battery terminal test results after recharging (I forgot to test the cables - will do so later if you think it's necessary):
- Not installed in car: 13.34 volts
- Installed in car, car not running: 13.20 volts
- Installed + car running: 14.42 volts
- Installed + car not running: 13.17 volts

Is the dip to 13.20 volts after being connected normal?

Glad to see it's receiving a charge from the alternator while running. Is 14.42 volts about right?

I'll check the battery voltage again after supper.

One thing I noticed - when I bought my battery charger last November or December and charged the previous / old battery it took about 10 hours to charge and reached 100%, and the charger said "full" then shut off automatically.

This battery charged for about 20 hours, and stuck at 90%. The charger never said "full", never shut off.

So... battery might be shot?

Your thoughts would be appreciated!

[shorod]

None of those readings would raise a flag with me. They all seem pretty good. But, yes, letting it sit in the car for awhile will be a good test. Also, if your multimeter has a "Min" setting, use that, have it connected across the battery, and start the engine. The "Min" reading should tell you how low the battery voltage dropped when the starter was turning over the engine. If your meter does not have a Min feature, then have someone else start the engine while you watch the meter to see how low the voltage drops. If it drops below 10.5 Vdc, your battery is suspect.

-Rod

[Gardd]

13.08 this morning after sitting overnight.

Thanks much for the tip re: the min setting and 10.5 volts while starting the engine. I don't know if this meter has such a setting but I'll take a look. If not I'll have someone start the car while I watch the readout.

I don't like that anticorrosive gel that the mechanic put all over the terminal posts & cable clamps. There's lots of it and I had to scrape a bit off the terminal tops in order to be able to get a reading with the meter probes. I wonder if this gunk has something to do with the battery only reaching 90% on the charger.

I'll watch the battery levels this week and on the weekend I'll clean the gunk off the contact areas, put the battery back on the charger and watch how it does. Not sure what to use to get the gunk off; I'll have to think about it. It's like glue and probably not water soluble.

[danielsatur]

How old is the battery, it might not be holding a charge like it's once did!
Any Auto parts store will do a battery load test for free,

[Gardd]

The battery's about seven months old.

[Gardd]

Um... I think I know why the battery discharged.

I'm not at home right now to check it out in person but I just got a call saying the cabin heater fan came on all by itself a few minutes after the car was turned off.

This is the first time one of us has seen this happen but I think it's probably the reason why the battery discharged last Saturday night into Sunday - the fan must have come on while we were not in or near the car and it ran without our knowing until the battery finally pooped out.

I'll check the car as soon as I get home from work in a few hours but my immediate thought is that perhaps there is a problem in the ignition switch - after all, doesn't it control power to the accessories?

Anyone ever seen this kind of thing happen before, where the heater fan comes on all by itself when the car isn't running & accessory power is off?

How would I go about testing this, or should I just have a mechanic look at it? Is there a blower control module or relay that I can look at myself?

I'll post again after I've checked the car out myself. Maybe for the time being I'll have to pull a fuse in order to stop the fan from coming on. Not sure what else in the car would be on the same circuit but I guess I'm gonna find out soon.

FYI I checked the car & battery charge this morning before I left for work and it was okay, the fan was not running.

Sheesh.

[Gardd]

Buddy of mine just e-mailed and said it could be relay #23 gone bad in the box in the engine compartment. I'll take a look when I get home.

[danielsatur]

Some unswitched circuits are connected to BAT fuse's, see owners manual.

1) Disconnect the Neg side of the battery and connect an AMP meter in between, check on how many Amps are being drawn with ignition key off.
2) Isolate BAT fuses one at a time until there's no amps being drawn.

[Gardd]

Got home, yup the blower fan was running with the car off.

I pulled the relay from the #23 position, which is "Blower Motor Relay" according to the owner's manual; nothing else on this circuit. Fan is off now.

Battery dropped below 12 volts with the fan on since this morning so I pulled it and it's back on the charger.

I took a close look - I think the battery be faulty even though it's relatively new. I read reviews of this battery model (a Canadian Tire house brand) and some rate it highly while others said it's garbage and they went through battery after battery while still on warranty.

There seems to be a few tiny droplets on top of the battery but I don't know if it's really leaking acid or if I'm just seeing a bit of moisture that accumulated under the battery cowl. If it's faulty that would explain why it wouldn't go past 90% on the charger earlier this week.

I don't have any litmus paper - is there a way to test the droplets to find out if they are indeed battery acid?

I'll look into the BAT fuse thing after I've recharged the battery and bought a new relay on the weekend.

[danielsatur]

There's probably another relay of same type in the engine compartment you can roll with.