Need some help -

Engine is warmed up and when I stop for a light or what ever reason -

The interior lights dim, wipers slow or stop, and rev go down a bit.

I'm thinking alternator is the problem but how and what can I check to be sure.

 

sounds lika a alternator. is that all its doing? is the raido going off and on any other problems. or it could be a dead battery.

 

it starts fine, I will check the voltage of the batt today while it's charging and see. I had the O2 sensor replaced ( and a bunch of other work a couple month ago) and code 41 - O2 sensor is still coming up.

 

Does the battery/charge light ever illuminate when the car is running?

Sounds like an alternator problem; however, start with the basics first.

First, thoroughly clean the battery posts, connectors, and ground wire. Next measure the voltage across the battery posts with the warm engine idling. Compare that voltage to what you get when the high beams are ON and blower is turned to MAX. What values do you get?

 

This could be a fuse 15 issue. Damaged wires behind the engine will cause low alternator output, false oxygen sensor codes, and other problems. Click the link in Ron's signature above.

 

14.4 volts at the battery while running
13.8 volts at battery when off.

 

What happens to the voltage with high electrical load as I mentioned in my earlier post?

 

Some dimming of the lights at idle with everything on is to be expected.

If the wipers stop with 12.0 or more volts at the battery, something is wrong with the wipers or the wiring to them.

 

high beams, radio, wipers, four ways, interior light on

14.32 volts at battery

 

Did you need to rev the engine to maintain that high voltage. If not, did your light dim as mentioned in your thread title? If not, when does this problem occur?

I'm starting to think you may have a low idle problem. Have you cleaned the IACV? Is your ignition timing set to spec? Are your plugs, wires, cap, and rotor fine?