2001 i30 Lights dimming
 

Hello everyone,

Was driving my 2001 i30 tonight and noticed that the headlights are dimming really slightly. The check engine light is on for an emissions problem and I noticed during the daytime, it dims very slightly as well.
This happens almost exclusively when the car is in Drive and sitting at a stop sign/ light.

I was thinking it might be related to an idle issue, since last summer, the IAC valve on the car went bad and took the ECU along with it. I had the IAC valve replaced with an aftermarket one and the ECU replaced with a unit from the junkyard. I got the job done at an infiniti dealer and after it was done, they said the car will run but they weren't able to reset the idle correctly. I do notice that the car idles differently now since then but since the car is basically a beater (210,000 miles) and i'm a broke college kid, I figured it wouldn't be a problem.
Could the aftermarket IAC valve going bad after a year be the source of the problem? I'm thinking I could replace it in my driveway.

What I don't want to happen for the idle to drop out and the car to stall while I am out on the road.

It sounds like your alternator is not keeping up with the demands of your cars electrical system.I'd start with your local autozone or whatever is in your town and have them check your battery/alternator.I'd start there first at least.Let us know what you find.You can also do an idle relearn on your own just search the forums.Its actually easy.

Thanks for the reply, I actually just had the alternator replaced back in January. It was an OEM replacement unit so i'm thinking it's not the alternator.

Start by checking the voltage. If you don't own one, I would think that in a college environment that someone taking electrical/electronic courses would have one you can borrow.

But first, check that the alternator belt is in good shape and tight. Tight translates to pulling or pushing on the belt in the center between the a/c compressor and the crankshaft pulley with a 20 pound force and the belt deflects no more than .3 inch, ideally .2 inch. This has to be done from underneath.

Then check the battery voltage while the car is not running. A good, fully charged battery will measure approx 12.5 volts.

Start the engine and check again. With the engine idling, the voltage should be about 14.2 volts. Specifications are 14.1 to 14.7. If you rev the engine, the voltage should not change.

Start turning on things in the car, in fact turn everything on that you can. Headlights, bright lights, air conditioning, blower fan on high rear window defogger, hazard flashers, windshield wipers, roll the windows up and down and anything else you can think of. The voltage should still be within a tenth of the 14.2 or whatever you had.

If any of these things are not right, the alternator is junk.

A common misconception that people have is that because they have replaced something, such as the alternator in this case, the part cannot be bad. DO NOT EVER fall into that trap. And what is worse, rebuilt replacement alternators and starters have an extremely poor reliability track record.