Your test method will not work. Beginning with some '97 models, the computers can draw up to three amps for up to 20 minutes after the ignition switch is turned off. After that, they go to "sleep" mode, then Chrysler says a good, fully-charged battery will be able to start the engine after sitting for three weeks. That allows up to a 35 milliamp, (.035 amps), draw for the multiple computer memory circuits. Now that is the industry standard unless specified otherwise by the manufacturer.
The problem with going to sleep mode is the computers wake up again any time the circuit is broken, then they need up to another 20 minutes before the draw goes down. Breaking the circuit includes disconnecting the test light and reconnecting it, moving the red meter lead from the dedicated 10-amp jack to the common jack, and even simply switching ranges on the meter.
The way to get around this is to use a small clip lead / jumper wire to short out the amp meter when making changes, so current flow is never interrupted. A test light is not going to work. Those with the standard, common incandescent bulb require considerable current to make the filament glow. You could have a draw that exceeds the limit but is not nearly enough to see in the bulb. You need to measure current draw with an inexpensive digital volt / ohm / amp meter. Most of them have a common jack for all of the ranges except the highest current range. Typically, you'll find the highest current range on the common jack is 200 milliamps, or possibly two amps, and will be fused accordingly. If you start out on that range and the vehicle is drawing three amps, that will blow the meter's internal fuse. That's why it's standard practice to start out of the ten or 20-amp range, but that means moving the meter's red lead to that dedicated jack. You can read the higher current values, but you'll give up the accuracy.
Start out on that highest current range, then wait until the current draw drops significantly. As I mentioned, that can take up to 20 minutes. Now it's okay to switch to a lower scale for more accuracy, but you can't break the circuit. Assuming you removed the negative battery cable and the meter is connected between the cable and battery post, leave that in place, and add the jumper wire to the same two points. Now it is safe to move the meter's red lead to the common jack.
The same holds true if you want to switch the meter's range switch. All meters use a "break-before-make" switch design. With that, as the switch is rotated, the connection is broken to one range, then, as you continue turning it, the connection is made to the next range. No two ranges are ever switched on at the same time. That simple, very tiny gap between the contacts is more than enough to wake the computers up again. That's why you must connect the jumper wire while making changes to the range switch or red lead.
At 35 milliamps draw, you'll be able to start the engine after three weeks. That's what Chrysler says. In fact, I've found that my '93 Dynasty can sit for over two months, and my '14 Caravan sat over the entire winter last year, and still started in the spring. That three weeks is the minimum, but the point is the battery will not go dead overnight like yours is.
Once the computers have gone to sleep mode, you can start removing fuses. Be aware if you have a second fuse box inside, the interior lights are going to be switched on when you open a door. There can be so many bulbs that it's easy to exceed the meter's fuse rating. The common 194 "peanut" bulb, like those found in glove boxes, draw roughly half an amp, so if you have six of them in the doors and on the roof, that's three amps total.
When watching for current to drop to sleep mode, if it's still higher than 35 milliamps, wait a few more minutes. Not all computers shut down at the same time.
Typically, when a defect is causing the battery to be drained too quickly, you're not concerned with small amounts of current. What I mean is if 35 milliamps is okay, but you find 50 milliamps, for example, that is not enough to drain the battery. Even a glove box light that doesn't turn off won't be enough to prevent starting the next day. Expect to find a good two or more amps of draw that doesn't go away. Even most lighting circuits are not suspect at first. I never watched a glove box light, but others, like interior lights, are turned off automatically by the Body Computer if you forget to do that. Probably the better suspect would be a computer that isn't going to sleep mode.
Do your test again by removing fuses, then tell me what you find. For safety systems like air bags and anti-lock brakes, there will be two fuses for each of them. Remove both fuses when checking those computers.
Here's photos of the procedure I use. In the first one, the negative battery cable has been disconnected, then the amp meter is connected to the battery post and cable. The green clip lead is just used so I don't have to hold onto the red probe. The meter is on the highest current range, 10 amps. That requires using the special 10-amp jack for the red lead. Current is 1.46 amps. That's enough to drain the battery in a day or two.
In the second photo, nothing has been changed except the computers have gone to sleep mode. .04 amps is close to the allowable limit, but to get another decimal place of accuracy, we need to switch to a lower range. To do that, in the third photo, the red jumper wire has been added between the battery post and the cable. Now, no matter what we do with the meter or its leads, the circuit will not be broken. The meter is reading 00.0 amps because current takes the path of least resistance, which is through the red jumper wire.
In the fourth photo, the red meter lead has been moved to the common jack, and the range switch is turned to the 200 milliamp range. Either of those would have broken the circuit if the red jumper wasn't in place.
Finally, in the fifth photo, the red jumper is disconnected on one end. Now current has to flow through the meter. It's reading 42.8 milliamps. That's the same.04 amps we found previously, but with more decimal places of accuracy.
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Monday, September 30th, 2024 AT 3:39 PM
