Too old to be tested? Do they think everyone threw out their test equipment because they hung a new calendar on the wall? You need to find a different mechanic. I drive an '88 Grand Caravan so I know I'll get home again. When the Check Engine light turns on, it means the stored fault code is related to something that could have an adverse effect on tail pipe emissions. There are other codes that do not trigger the Check Engine light. Almost all Chryslers use a gauge on the dash for the charging system. For those that also have a battery warning light, it is just to get your attention since most people don't watch the gauges very closely. The battery light actually has nothing to do with the condition of the battery. It refers to the alternator recharging the battery after starting the engine and while driving. The voltage regulator, which runs the alternator, is built into the Engine Computer where it can be monitored. On some models when a problem is detected with the alternator, the Engine Computer turns the Check Engine light on because low system voltage, (as the battery runs down while driving), can affect sensor readings and the injectors' ability to open fully. The fuel pump will slow down too. You might be able to drive that way for an hour or so with a really good battery, but that hour should be used to get home or to a repair shop. Rather than waste a lot of time worrying about the Check Engine light right now, lets start with the charging system. If both warning lights came on at the same time, there's a real good chance this is going to be a fairly inexpensive repair. Hey, it's an older Chrysler! (I love these cars). Start by grabbing an inexpensive digital voltmeter. Since the engine starts and runs, we can skip over half of the tests and go right to the back of the alternator. There are three wires on it. You should find full battery voltage on the fat black output wire all the time. That's the one that's bolted to the back. For the other two, there are two small metal tabs coming out of the black plastic block that's bolted on the back. Measure the voltages on those two small nuts on the two tabs, but you MUST measure those with the engine running. One of them will have full battery voltage. The other one is the secret. It is supposed to have less voltage but not 0 volts. If you find 0 volts, the diagnosis is done and I'll post a photo of the repair part. On some engines you can do the repair without removing the alternator from the engine.
Monday, March 14th, 2011 AT 7:08 PM