01/13/2020
We had a vehicle in the shop recently with electrical problem. We typically do not see this kind of problem a lot so I thought I would share how our shop would diagnose a dead battery no start conduction. The vehicle we are diagnosing is a 2010 Chrysler Sebring . The vehicle was towed to the shop with a dead battery. We start by opening hood and look for problems like a belt has failed or any other component that was instructed that alternator from charging. We also look at the condition of the battery and cable ends (This vehicle's battery is located in the left front fender) or any aftermarket appliance that could be installed, let's say not so professionally? There are no problems notice and no aftermarket devises. we used a jump box and the vehicle started so we drove it in to the shop for farther testing. Once in the shop, we used a digital volt ohm meter (DVOM). With the engine running with the aid of the jump box , we installed the DVOM leads to the vehicle battery jumper terminals on the left front strut tower. The meter is reading 14.5 volts. We removed the jump box and the vehicle will continue to run. With a quick check it appears that the alternator is OK and wiring, at least to the jump terminals? We focused our attention to the battery. We have to remove the left front wheel and the inner fender to gain access to the battery. We first noticed that there is dried fluid trail going down the battery and the condition of the battery terminal ends.
Battery Terminal
• Terminals are corroded. We removed the battery, cleaned the terminals and the top of the battery. (the substance along the battery was not acid but most likely terminal cleaner used by a previous repair person?). The battery has a sticker that reads 1/18, so the battery is not that old. We charged the battery and tested the battery with a full charge. The test PASSED. After cleaning the terminals we found that the negative cable end was not repairable so we replaced it.
With the DVOM leads stilled on the vehicle's jump terminals, we have 12.5 volts and 14.5 volts with the engine running. Problem fixed, put the car back together, pull it around front, call the customer, collect the money and move on to the next one right? WRONG!
Sadly. I assume that a lot of repair facilities would stop here thinking that electrochemical corrosion between terminals and the battery post were causing a voltage drop? The alternator was not able to charge the battery and that's why the battery died? That may be true, we repaired several vehicle because of that issue. But there is a test that is simple to do, in most cases, it called a draw test.
I've fallen victim to skipping the draw test too in the pasted. But after a couple of times of having to talk with a not so happy Customer with their vehicle being towed back to a couple of days later is the hardest thing to do. You can explain everything you did and that all cleaning and testing that needed to be done, but the vehicle is back because you stopped testing to soon.
We have not fully tested the alternator yet. Using a hand held Battery Charging system tester we are able to look at and give the alternator a good work out.
The alternator is charging, but a diode has failed causing a lot of a/c ripple. (Note lower left of picture). This could also discharge the battery. Testing for a battery draw also showed us that there is a parasitic draw that will drain the battery in a couple of days.
