For those with a good memory, my SC430 had some ML amp problems last year that caused a number of issues that meant I found out to change the car battery (!) and also install a new ML amp.

So I like to think I'm an expert on the SC's electrical systems.

Anyway, enough with the background - I had to rush out this morning, and car wouldn't start - no power at all.

Whipped out battery and put on charger - checked voltage after 1 hour, and it read about 12.4 volts but ticking down rather than remaining static.

So I reasoned that the battery had somehow discharged overnight.

This came with no warning, and perfect starts every time, ML and audio behave perfectly (put in new/recond ML amp from ML).

I must have a drain somewhere that suddenly appeared overnight, and I've checked all the obvious things - lights (boot/trunk, interior etc..) and they all okay.

The only two things I did differently last night was leave the headlamps on 'Auto' and I didn't lock the car doors, so may not have shut door fully so could have been interior left on overnight.

My question is - would leaving the car unlocked (with all doors shut fully) cause an overnight current drain ?

And is leaving the headlamps on 'Auto' likely to drain the battery (had visions of lights being on during the night - but never checked) ???

Have put old battery in - and started fine first time - so not an ignition related issue.

110k service due soon, perhaps it knows ?

Thanks

 

I leave mine in the garage unlocked with the headlights left in auto and never had a problem. I'd check the amperage drain while the car is totally turned off and see what the drain is.

 

I have a couple of questions and a thought.
When you say "you checked the voltage" and it was 12.4 "but ticking down"

1. Was the battery connected with the car or was it disconnected?
2. Analog or digital V/O meter?
3. Was the ticking down obvious, i.e. within a few moments it down to 12.0 etc?

If I understood you correctly, "have put an old battery in" you installed a different battery and the car started right away. What I'd like to know is: if you put the battery that would not start the car back in, and if it starts the car now?
If so, then you need to look at the battery cables, the connection to the battery and connection at the main ground.

If I misunderstood you, then disregard my comment.

 

I took the existing battery (only 10 months old) out and started charging it then checked the voltage with a digital multimeter after an hour - mostly as an afterthought to be honest.

I only held the meter on the batter for about 10 seconds, but it was ticking down 12.49 12.48 per second almost - so concluded that if I waited 49 seconds it would be 12.00 volts (however wrong that may be)

The battery that came with the car, but has been in the cupboard for the past 10 months, was pressed into service and the car started fine.

I should check the cable you're right - just can't think that anything happened in the past 24 hours that would suddenly discharge the battery ? (Except leaving the car unlocked ?)

 

Next is to put the multimeter in between the neg battery post and the neg cable and read what's being drawn by the car AND, in which state, that is, locked, unlocked, alarm on and off. I'd also try leaving a door ajar, maybe trunk lid ajar and one or two of the overhead lights just to see what's being drawn. Finally, I'd also want to make sure the generator is doing its job keeping the battery charged. If the alternator died or is not functioning to specs your battery could have sucked dry.

 

This has happened to me a few times. It was always that a door was not closed. Most of the time was the passenger side. One time I left the trunk door unlocked thinking I was going to put something in the trunk, but didn't.

 

Don't rule out a bad battery either. Take it in and get it load tested. You could have lost a cell.

TOXIC

 

Batteries, what a subject - all of us have our own preference, but, is it the problem? 23 months ago, my original battery on 2004 SC died - could tell it was going by the way it turned the engine over during it's last days. Based on personal experience in this forum, picked up a "Duragold", with 2 year replacement warranty. For some odd reason, after 23 months it died, charged with Battery Minder and two days later it was dead. Returned to Autozone and they replaced it at no cost (good timing). This is a $150 battery!!! You never know.

 

Battery drain draw should not be more than .070 Amps. Start pulling fuses out if it's over that amount.

 

OUTSTANDING! What it should be and how to islate the problem source.

Thank you Fiend

 

Wouldn't you know it.....I have more thn one drain. I have isolated the 14 amp drain to one of three circuits and I can get it down further easily with fuse removals and measurements fo current draw. Problem is I never see a drop to less than .55 amps. The car used to hold a charge for a few days and I think the .5 amp draw was working it bacck then. I'll find them both and get back to you all.

I suspect that the 14 amp load is a "normal" draw for some circuit that is energizedm my a relay that is malfunctioned. How cpuld I have an "extra" 14 amp draw and not pop a fuse when the circut is fused tp 30 amps? Hummmm!

John

 

OK, Grande Finale.

My original battery showed signs of having lived it life valiantly. It was swollen with sulphate so it held a diminished charge. I replaced it though I later discovered that it would probably lasted a while longer. After replacement my problem actually did not go away though it started and ran ok for the rest of the day. Next morn.... same olde crap.

I got rid of the "phantom" current drain of 14 amps when I pulled the "Theft deter and door lock fuse". Turns out that my ECU is messing up and doing it thru the passenger door lock mechanism. I disconnected the door lock and installed the fuse and my 14 amp drain is still gone. My manual door lock and door open features are still fully functional. I am going to live with this fix till I can find a good price on a replacement ECU. Anybody parting one out?

Now for the FINALE NOTE. My new battery is defective. After being charged over nite it reads weak on the specific gravity bulb. Being a HUGE battery even this 25% charge spins the motor over easily. Max charge seems to be 12.48 volts. Sitting in the car with the neg term removed that terminal voltage will drop to 12.1v over night. Bad battery.

Now the word of caution: I once measured .6 amps drain. After I closed the door, duh, the drain was .37 amps. That is not the .007 that has been sighted as the norm. Maybe I have still another problem that I had been dealing with over the years....need to run the car at least once a week.

Thanks for all your help.

Start at the fuse block under the hood. 10 MM socket to lift the block so you can disconnect the major feeds. 160 amp fuse and such. After finding that path go under the dash and start pulling the major 60-30 amp fuses till the drain goes away. Then startr pulling the small fuses to locate the device/circuit leg.

Used a digital meter.

HTH

 

It never ends. New battery(again), right side door lock disconnected. Very odd....current drain that fluctuates from .4 to 1.1 amps. I am looking forward to the explanation on this.

Still working the problem.

John

 

Until you clear up the drain issue, you will continue to waste batteries. That is a major drain indicating that something is definitely gone sour.