Automotive Forums

I have a 2000 Oldsmobile Intrigue and I notice at night that while driving my head lights and all my dash lights will dim, along with my fan for the ventilation slowing down, all intermittently. It has become a distraction and I am worried that the lights will go out while I am driving on some back road. What could be causing this problem? I have replaced the battery and posts from the cables and the problem is still occuring.

Thanks for any help,
Tim  

What you describe appears to be caused by an intermittant charging system failure. That's a broad statement. It could be caused by a poor wire connection just as well as a faulty alternator/(or)regulator.
The wires to and from the alternator,battery cables,and ground connections and also the feed into the fuse box. They all should be checked.
I dont think your car has a charging indicator on the dashboard? Just one of those lites? If you could hook up a dial type then you would know if it is a charging system problem or a wire feed problem.

Thats the problem with an intermittant problem.If you don't have the tools ready right then and there to test it becomes a guessing game.
But a voltmeter already hooked up to the Alternator and ground will tell you right away if thats the cause the next time it happens.  

We would begin with a physical examination of the battery.  If ok, proceed to the load test.  Load the fully charged battery (12.6V after a surface charge is removed) to 1/2 of its CCA rating for 15 seconds.  Voltage should be above 9.6 temperature compensating at the end of 15 seconds of load.  Next performance test the alternator to make sure it is working to its specified capacity.  If good proceed to the intermittent tests of the charging system.  Connect one voltmeter to the output studs of the alternator, iee... the positive output terminal and the frame of the alternator.  Run those leads into the vehicle and connect to test voltmeter number 1. Next take another voltmeter and connect to the input circuit of the alternator, iee... the small feed wire going into the alternator from the ignition switch.  Run those leads into the vehicle and connect to test voltmeter number 2.  Locate these voltmeters so that they can be eaisly read from inside the cockpit while operating the vehicle.  Drive this vehicle until the symptoms reoccurs.  Time is on your side, since a problem like this always gets worse and occurs more, making it easier to diagnose.  Remember a more stable problem becomes easier to diagnose.  These voltmeter's tests will indicate where the problem is.  If voltmeter number 1 goes to 12 .6 volts while voltmeter number 2 is also at 12.6, alternator is bad.  If voltmeter number 2 goes to "0" then input to alternator internal regulator is lost, and problem is then in the ignition switch energize circuit.  As a matter of good diagnosis and troubleshooting, finish with a performance test of the alternator, to make sure it is performing to its capacity.