Alternator woes

I have a 90 Lesabre that's acting weird. From a cold start there's no problems. As the car warms up, the alternator light indicating low voltage slowly (i.e. not a solid light, but a low glowing light) comes on and the lights dim. Racing the engine seems to help, but you can't drive it that way. Do alternators usually die in this fashion or could a belt/tensioner be loose. There seems to be proper tension and no visual indication the belt is slipping.

Sometimes a bad diode or rectifer in the alt will make it act like that. It will still work, however it will not charge at the full amp or 13.8 V. It will be more like 12.2 V which will not keep the battery charged while using accessories. Check the alt output with a DVM, to see what it is putting out.

On my '87, the connector with the field wire was loose. For the time being, I stuffed some aluminum foil in the end and plugged it in - it's been running great for months like that, until I can get around to replacing it.

It'd be best to check your voltage, but while you do it, try pressing down on this connector if you can. If your voltage jumps up, that's your problem.

Take the alteernator off and go to a major auto parts store and have it checked. The regulator is in the unit too.

Temperature dependent -- it may be corrosion related.
1. Use a volt meter to read the voltage between the output on the back of the alternator and the negative terminal of the battery.
2. Use the volt meter to read the voltage between the + and - terminals of the battery.
3. Let the auto warm up and take the measurments again.
4. If the voltage at the back of the alternator stays the same and the battery voltage decreases, replace the cable between the alternator and battery. Usually corrosion adds to the resistance of the circuit and becomes higher with increasing temperature.