After car runs for 5-10 mins, battery light comes on and stays on. Stop car and restart, light stays off for 5-10 mins and comes on again. Battery replaced last month. Had All-Parts Automotive do the system test. When the light was off, they said alternator was fine and battery fine but low charge. I drove 10 mins, light came on, I had them test with light on. Test said battery was bad. Stopped car, had them restest and it says battery is ok. Battery connections seem tight and look ok. Car is a 1997 Sebring convertible. Any idea what the problem is?
Wait until the problem occurs, then measure the voltage on the two small wires on the back of the alternator. They will be two wires that are plugged in, or two wires that go through a black plastic block, then appear on two tabs that are held on with two very small nuts. The voltages will only be there when the engine is running.
One terminal must have full battery voltage. The secret is the other wire. It should be less than the first one but not 0 volts. Use an inexpensive digital voltmeter to measure them, then holler back.
January, 15, 2011 AT 11:57 PM
Thanks for the reply and suggestion. I appreciate it.
There are 3 wires, but I assume we're not talking about the big red one. Of the other 2, 1 was green with an orange tracer- it read about 12.9v on my analog meter (same as across the battery terminals). The other wire was solid green and 0 volts.
If you're going to say the alternator is bad, can you tell me why the store test said the charging system was ok (13.80v 29.7A no load and 13.81V 62.6A Loaded)?
January, 16, 2011 AT 12:21 AM
Yup. REAL common problem. The brushes are worn and making intermittent contact. The testing has to be done while the problem is occurring. During their test, they caught it while it was working.
If you can find the parts, you might be able to replace the brush assembly without removing the alternator from the engine, at least that could be done on the older stuff that I drive. I've done this many times on cars I put "bugs" in for my students to troubleshoot.
Here's a photo of what the assembly looks like. You don't have to remove the terminal block as I did in the photo, just the three screws.
January, 16, 2011 AT 12:24 AM
Here's what the back cover should look like on your car. Notice the "ND" in the middle for Nippendenso.