Interior lights problem...

Ok guys, question.
My interior lights flicker whenever my 2000 jeep xj with 152,000 miles is on, but when its off, and I turn on the dome lights, they don't flicker. The headlights and fog lights (wired to their own relay) would also SLIGHTLY flicker. I got a new battery, new PCM, new grounds and its still there. The alternator was tested at autozone and it passed. But then again, so did my old battery which the dealer tested bad. I'm pretty much out of money so I need help badly.

Any ideas?

Did you replace the PCM because of the flicker or for some other reason?

The voltage regulator was bad, the dealer confirmed it, thats why it was replaced.

The voltage regulator portion of the PCM circuitry rarely fails. Do you have the voltage figures prior to the swap?

If exchanging the battery and PCM was supposed to repair the flicker, I would take your Jeep back to the dealer. Just be sure they understand that you are not authorizing any new work without your specific okay and then let us know what they say.

The battery should absorb random voltage spikes to some extent so all of the connections to the alternator and battery cable connections should be confirmed shiny clean, and tight at the battery and termination point.

One other thing: is the flicker steady or somewhat random.

Let us know.

Well, I ruled out everything except the pcm basically. Nah, the issues I was having, I told them, I told them what I had tested and replaced, they retested everything and came up with nothing besides the battery was bad and that there was a 1.1V diff between a sensor and the PCM or something like that. They ran more tests and confirmed that the PCM was faulty. I cleaned and replaced any cable that needed so. As for the flicker.... Thats a good question, I'm not 100% sure to be honest, but it doesnt seem like its fully random, like it'll be good then not then good then not. it'll flicker all the time when the jeep is running. when its not its a nice steady flow of light.

It's probably the alternator. My guess is the rectifier has, or is failing. The rectifier is different than the regulator. Where the regulator monitors the system voltage, and adjusts the alternators field voltage to very the output in correspondence with the increase/decrease of engine RPMs. The rectifier turns the alternators AC voltage into DC voltage.

A little basic lesson on how alternators work....

An Alternator is different from a standard electric motor in that it doesn't have a permanent magnet. It uses two coils of wire (one fixed, and one that rotates) instead of the permanent magnet. They produce an AC voltage that will very in correspondence with the engine RPMs if left unchecked. The rectifier uses diodes to convert the AC voltage into DC voltage. The regulator monitors the system voltage, and varies the field coil to keep the output voltage within spec (the inchecking).
If the rectifier has a bad of failing diode (there are typically four) it can let a slight amount of AC through, or cause the DC voltage to pulsate. I believe the regulator can handle the pulsating DC and catch it to a certain point, but cant even see the AC voltages. Your battery also acts as a filter to help filter the minute pulsating DC out of a properly operating system.
Now if your getting some AC voltage into the system your lights would flicker (because incandescent lights aren't AC/DC specific), but your other electronics wouldn't detect it until it got so bad that it started frying stuff. You may be able to use a digital multimeter to check if there is AC voltages in the system, but that being said most cheaper meters are designed around 60hz AC, and if the AC frequency in the system isn't close to that it may not be able to detect it.

Now if it was that problem, wouldnt I have issues with keeping the battery charged?? Also is there any way to test if its bad without removing the alternator?

Well I'm just gonna change out the alternator tomorrow just to eliminate it if anything. Hopefully it fixes it

You said you were low on funds at this stage of your college career which pretty much describes most of us at that point in our lives. Another plan would be to see if you could find an automotive electrical shop and let them test the alternator. If the diodes are bad, they can probably change them out for less than the cost of a new or rebuilt alt although the cost of removing the alt might offset the potential savings. I would at least talk to a shop if you have the time. Just a thought.

Ok guys, so I did some trial and error deal today. Found out a wire was grounding out somewhere but I couldn't find where it was. All wires were fine, removed it, fixed 95% if it. Then put in a new alt and it was 100% fixed. Sucks that I had to do the alt but mine was the original at 150, 000 miles so just my luck If I didn't change it In a month from now when there's 3ft of snow on the ground it would have died on me lol