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Please Help! Car Dying Intermittently

My Toyota Corolla, 2006 keeps dying after long periods of sitting. Coincidentally (?) the issue has only occurred on weekends, after my 8-hour afternoon work shift. The first 2 occasions it made a quick clicking sound when I tried to start it (6 and 5 weeks ago, respectively). I replaced the battery; it was old. Then, the same issue happened two weeks ago. I had the battery checked at the site of purchase, where they also checked the alternator. Both reps advised me the parts showed up good on their meters. It died again the next day. So, I had a mechanic check every fuse and relay in the car to look for a draw on the battery using an amp meter. Readings indicated no significant drop in current draining from the battery while any were unplugged. . . I don’t use a remote control unlock button (one professional seemed to think this might be relevant), and I have checked to make sure no lights were left on, even in the trunk. (Also note - I have seen no drop in performance when driving vehicle, nor any change in air conditioning or light brightness). I’m lost where to take it from here. Please, help!

If the battery is draing down over an 8 hour period, you certainly have some circuit that is on and draining the battery. I suspect the igition switch has a short to possibly the accessory position, such that it is energizing all of the devices that get accessory power. See if you can get a clamp on ammeter over the positive battery cable, then slighty wiggle the ignition switch. You’ll have to have someone watching the meter while you wiggle the switch

P.S. If you can’t get a ammeter, just gently wiggle the iginition switch and watch the radio or some other accessory device to see if comes on as your wiggling

What do you mean by the car is dying? Do you mean when this happens, then you turn the key to “start”, all you hear is a click, but the engine doesn’t crank? If it’s not the battery, then that symptom can also be caused by either a loose or corroded battery cable connection somewhere, a faulty clutch safety switch (or the auto xmission version), a faulty starter relay, or a faulty starter motor selenoid. My guess would be the starter motor selenoid, your car is about the right age for this. Not uncommon at all.

First of all you need to determine with 100% certainty it isn’t the battery. Is this the same battery that came with the car new? If so, you likely need a new one. Batteries seldom last more than 5 or 6 years, and the problem shows up when cold weather starts. As like now. If you have replaced the battery though since the car was new, when it gets in this condition, have you had the current battery checked with a “load test”. That’s the only way to determine if the current battery is good and fully charged or not.

This is not an easy one unless you can lie have a meter and how to use it.  If you did, you likely lack much experience with it on an automobile. 

 I find it hard to solve these.  I and others can make suggestions based on what they have seen.  

 Good Luck.

The current draw may be from a computer/module not going to sleep after the vehicle is turned off. Normally, these computers/modules should go to sleep after an hour of turning off the vehicle. If something doesn’t go to sleep it can draw the battery down.

In the past before vehicles had computers/modules one would disconnect the battery and install an ammeter or test light in series between the negative battery post and the negative cable to check for a current draw. And if one was observed then one would start pulling fuses/relays until the current draw was gone. But on todays vehicles with their computers/modules you can’t do that. Because if there’s a component that isn’t going to sleep and you disconnect the battery that forces that component to go to sleep. So when you go to check for the current draw it won’t be there.

On todays vehicles, the current draw has to be located without disconnecting the battery so if there is a component that isn’t going to sleep it can be located. And then you check for a voltage drop across the fuses to determine which circuit is drawing the current. I’ve sometimes used a high resolution infra-red thermal gun pointed at the fuses to determine if any of the fuses read a higher temperature than the others. And if a fuse shows a higher temperature than the others, that’s probably the circuit drawing the current.

Tester

Good point. If you reset the electrical system’s current distribution by disconnecting the battery to insert an amp meter – as is likely in newer cars – you won’t find out much. There are some amp meters commercially available that allow the measurement of current flow without disconnecting the battery, they use the Hall effect to do the measurement. They just clamp onto the wire and work by measuring how much magnetic field is produced by the current. But this kind of amp meter is usually not the kind sold in auto-parts stores and I don’t think they are available even at Harbor Freight. Most of the inexpensive clamp on amp meters only work for AC, not DC. The clamp on DC amp meters are geared to be sold more to electrical engineers and technicians than home auto repairers. The most common ones I’ve seen are made by Fluke. There may be a market opportunity for some savy investor to sell a reasonably price clamp on DC current meter to the home auto repair market.

And that’s another of your good ideas @Tester, using one of those infra-red temp monitors with a laser pointer on the fuses. I’ve never thought of that, but I’ll try it next time I need to figure out which circuit is using the most juice. Thanks.

As Tester suggested, "The current draw may be from a computer/module not going to sleep after the vehicle is turned off."

Current draw can be checked with an inductive clamp on attachment to a DMM, you do not need to break the circuit. Also Tester incorrectly indicated that you can measure voltage drop accross a fuse. A fuse is nothing more than a wire that melts on overcurrent. You will not be able see a drop in voltage accross a fuse.

You can however use an ammeter as I mentioned before. With the key off, measure the parasitic current. Then pull each fuse (one at a time) to see which circuit is drawing down the battery

Let’s see if this works.

For some reason the link doesn’t work. Go to YOUTUBE and look up parastic current draw and there’s a tech that shows how to use fuse voltage drop to locate the current draw.

Tester

A fuse has to have some resistance. Otherwise it wouldn’t work. So any fuse will have some voltage drop. Since the fuse can’t disturb the circuit, the voltage drop across a fuse in a 12 volt circuit would be in the range of a few millivolts, but that’s well within the range of even cheap DVM’s to measure. I got a free DVM from Harbor Freight in fact – one of their “buy something, we’ll give you this for free” coupon specials that can measure down to 1 mv.

Yes. A fuse has some resistance across it’s element. But a fuse that has a slight amount of current passing thru it causes that element to heat up slightly. And when that element heats up it causes a resistance. So you would see a voltage drop across the fuse.

Tester