Chrysler Repair: 1997 Dodge Intrepid: discharging problem, ammeter voltmeter, cable clamp

Question
Hi Roland,
I'm at my wits end with my son's 1997 Intrepid. For some strange reason the battery is being drained or is not being fully re-charged. The battery was replaced last winter. A few weeks ago, the car would not start. With a boost, it started and seemed to run well. When the car was turned off, we could not re-start without a boost.
I returned the battery to the vendor. They re-charged it and put it back in the car to do testing. According to them, there is nothing wrong with either the battery nor the alternator.
A few days after this, the car would not start again. This time I recharged the battery and put it back in the car telling my son to disconnect one of his battery wires whenever he parks. I was guessing that something was draining the battery even if the car was turned off.
Yesterday, the car started and ran a few times without incident. In the evening however, it would not start again, even after having disconnected one of the battery cables while parked. The car was boosted to start. During the driving following this boost, the car's battery light went on and the car sounded like it was going to die. After getting home, the car would not start again.
It appears to me now, that something somehow is draining the battery while the car is running since disconnecting the battery did not appear to do much.
Any ideas? I'm inclined to think alternator, but the Partsource guy said it was OK. Apparently the voltage regulator is incorporated into the alternator on this vehicle.
How can I determine what is causing this problem?
Help.

Answer
Hi Michael,
You have to check whether or not there is a significant draw when the car is off using an ammeter-voltmeter-ohmmeter device. You would put it in series with the disconnecting - post clamp (hook one lead to the cable clamp and the other to the - battery post). See how many milliamps are being drawn with everything turned off, all doors closed, lights off, etc. Then I would pull the fuse #13 (labelled M1 possibly) in the fuse box inside the dash and similarly measure the current draw (remove the left end cap of the dash for access. That would tell you if there is or is not a problem when the car isn't running. The draw should be less than 100 milliamps, ideally much less. The M1 fuse is for the courtesy lights and the memories of various modules. If you find a higher draw then try pulling fuses one at a time, beginning with the fuses in the box in the engine compartment, to see which ones are drawing excess current. Put them back after you note the effect of each one on the current draw.
Then I would reconnect the - clamp to the battery and measure the voltage across the battery with the engine running. It should be at least 14.5V if the charging curcuit is working properly. If there is a large short in a working circuit of the engine that could cause the light to come on, but it is more likely the alternator or the voltage regulation of the alternator (which is done by the engine computer).
You also could get a fault code readout about the system for free at an Autozone parts store if there is one near you, of for around $40 from an independent shop. Then write back with any fault code numbers ane with the results of your current measurements with each of the fuses pulled. Once we know which circuit(s) are drawing too much we can examine what are the items on that circuit and test them individually or consider the charging system as the problem.
Roland