Vlocity

I know, I know....another thread.

First and foremost, I have read a number of threads to get me off to a good start, but I have a couple of questions that remain.

The scenario is that the car is great for days at a time (weeks) and then is dead to the world after sitting for overnight.

Last night I put a multi-meter between the ground cable and battery and the result was a .75 ma draw. My understanding is that it should be 1/3 that or about .25. Still, I am a bit surprised that this would kill a battery overnight.
So that is my first question. Am I chasing a ghost at .75 ?

The next step was for me to pull each fuse in the front followed by each relay.
There was NO change always a consistent .75 ma draw. I also disconnected the additional accessory small cable on the positive side and no change.

I did not get to the fuses and relays that are in the engine compartment and will address that over the weekend.

I also plan to charge the Optima 1 year old battery and take it in for a load test, but as random as it is, I don't think that it's the battery.

SO any help would be greatly appreciated.

Ken

darth

Are you sure it's 0.75ma (i.e. 0.75 milliamps = 750 micro amps) and not 75ma? 75ma is more in the ballpark.

Bill

Vlocity

Sorry about that, yes 75ma.

And just back in from the garage and it is now down to 65ma, that after pulling and checking the fuses and relays in the engine compartment.

So is that enough of a drain to kill a battery overnight?

Or is the random problem not showing itself right now. I guess that is my main question before I go any further.

Thanks,

Ken

darth

What's the Amp/Hour rating on the battery? Have the battery load tested - parts stores up here will test the battery for free and give you a print out in the hopes they will sell you a new one. If the battery is good it shouldn't discharge that quickly with a draw of 65 ma. You may have an intermitten draw from one of the door switches, alternator diodes, or any other electronic device. It would be good to be able to monitor the current draw continually so you can catch the the extra drain when it occurs. One of the things I wish these cars had was a real ammeter in the dash that indicates positive/negative current. Maybe you can find a good instrument meter and connect it semi-permanently - they shouldn't be too expensive.

Bill

Vlocity

Darth,

Its a 48 Amp hour yellow top optima. I agree on the Amp gauge.
It looks to me like this is going to be one of those deals.

I'll post more once I have the battery checked. I'm sure I'll be looking for additional advice. I would rather do just about anything than chase an electrical gremlin. I'm probably weaker on wiring than any other section of repair.

Thanks,

Ken

rsscotty

I recall there was a factory technical recommendation on reducing current draw on 964 coupes. I believe it was removing a warning bulb in the clock for the cabriolet top warning. I can check the article at the shop on Monday if you need more info.

darth

The amp hour rating is just a general method for rating a battery. In your case, you say the battery discharges over night so about 10 hous, and at 0.065 amps your battery would be .065 X 10 = .65 AH nowhere near the 48 amp-hours spec'd if in perfect condition It would have to have a drain of 4.8 amps to be within spec. Either the battery is pouched or you in fact have a current drain of that magnitude. Sometimes the plates within the battery become physically loose and short causing a drain which can be caused by vibration. You could take the battery out hook up a voltmeter to it and shake it vigorously to see if the voltage fluctuates and in turn indicating a bad cell or loose plates. If you try this test be careful of the acid in the battery but I think those batteries are sealed so you should be OK. One thing to check is if you've had an after market radio installed or suspect the theradio has been worked on, there's a green shielded alarm wire which often gets cut by the installer. If it's dangling behind the dash and the center conductor shorts to a metal gound point or the 2 conductors short it may cause a current drain. Mine would trip the alarm on real windy days while the car was parked. Somehow the wind was getting into the cabin and blowing the wire around causing the center conductor to short to ground and setting off the alarm. Insulating the 2 wires from one another and any metal ground point with electrical tape fixed the problem

Bill

Vlocity

I have that technical bulletin and it is supposed to reduce the draw as you noted by 10ma. I may do that at some point in the future. Thanks.

I had that thought as well, this is an Optima battery which is the spiral cell design. I plan to have it tested tomorrow, but I have yet to fail one of these. The battery that is in my track car is now 7 years old.

Thanks again for the insight, the drain I was seeing last night and tonight is not enough to kill the battery overnight. Of course, we tried to start the vehicle, open and closed doors and hoods etc. so any of those things could have interrupted the high discharge culprit.

I'll keep you posted.

Ken

darth

Just a word of caution if you decide to go the with connecting up an ammeter semi permanently. The meter should be able to handle the maximum output of the altenator - probably around 60 to 100amps and the wires should be the same guage as the red wire that goes to the battery you're taping into. And make sure the wires you connect are secured and can't come loose. Also, search on "big green wire" - it hasn't come up lately but if I remember correctly others had battery drain issues associated with it which may help you.

Bill

darth

Ken

I've had second thoughts about my suggestion about the ammeter based on your comment about limited experience with tricity. Rather than that method, continue measuring as you've been doing but try not to interrupt the connection to the battery by connecting the meter first before you disconnect the ground cable, thereby not interrupting the connection and reseting any unusually hi current flow.

Bill

Vlocity

I had the battery load tested this morning and it is perfect. Showed 798 CA on a 810 CA when new battery.

I understand, I went and purchased a meter with the inductive style clamp so that I don't have to disconnect the battery. Initially I was showing the same 65 ma draw, went back through every fuse and every relay. No change. Started the car drove around for a few minutes and came back, the draw was slightly higher.....but I believe there are some relays that stay energized for a while. Watched a little football, went back out and the draw has settled to within spec at 23ma.

One other thing that I did was to take my lazer pyrometer and shoot each relay to see if there were any hot ones. None.

So I guess I am back to a cat and mouse game. I am starting to think that there is a relay sticking intermitently. I plan to drive the car as normal and throw the inductive amp tester on it each time it comes to roost and see if I can catch it acting up and then quickly use the pyrometer to see if I can identify a hot relay.

Any other thoughts are welcome.

Thanks,

Ken

darth

I'd do a visual inspection for bare wires rubbing against the chassis ground, moving mechanical parts (i.e suspension) or other wires. Around the exhaust or engine where heat would aid in eroding insulation from the wires. Relays, if the contacts are clean shouldn't show any heat unless there are massive amounts of current going through them, as resitance at the contacts is necessary in order to produce a voltage drop and in turn heat. Poping the tops off the relays and visually inspecting for discoloration (i.e. blue or black) at the contacts is a telltale sign of a relay which has been over heated due to current.

Bill

Richard Curtis

Remove the underhood bulbs (both trunk and engine compartment), and then see if that cures your problem. Did for me.

galenmoloney

I also removed the both underhood bulbs and that worked for me, the draw dropped from 1.4 amps to .02 amps. For some reason they were staying on. Now the alarm won't work correctly, it starts blinking when I lock the car with the bopper(fob). One step forwards, two steps backwards!

Vlocity

Back to basics here and I have another question.

The alternator light is not on, but when I test the voltage at the battery with the car running the voltage is only 13.5 volts. I see that the specification is 13.8 to 14.4. The voltage does NOT increase with engine speed. When I turn all of the lights on and run the defroster and heater fan on hi the voltage drops to 13.0.

Is it time to replace the alternator or are these OK numbers for real world use.

Thanks,

Ken