I have an 01 Tracker with a 2ltr that has started doing something weird. A couple minutes after starting it the lights both inside and out will start to pulse rapidly. This can last up to a couple miles and sometimes comes and goes but only seems to do it when the truck is cold. Somedays it doesn't do it at all. RPM doesn't seem to make a difference and neither does turning on the headlights verses letting the auto on turn the lights on. I'm afraid that it is going to let me down one day soon in the dark. Any ideas???

have your battery tested first, then test the alternator, could be the internal voltage regulator,

but the last time this happend to me, it was the batt. and without getting into too much mechanical detail, the alternator needs voltage to  work, if the batt is failing, it causes voltage drop as the alt tries to suck power from it so it can charge. i know it sounds strange, but that's how it works.

but anyway, test your battery first.

-Lance

Thanks Lance, I had a feeling it may be batt related. Volt reg would be either good or bad would it not? Do they go random when failing?

that's right, and if it was the alt failing,chances are you would see the idiot light come on 

and, if the shop has the right tools, they can check the batt and the alt at the same time.

-Lance

Mine did the same thing and it ended up being the alternator.

I put a new Optima in mine that I got for another vehicle as I haven't had time to get into a shop and I haven't had any flickering whatsoever in the last couple of days. The other batt did look pretty old so hopefully that got it.

My first thought WOULD be the alternator on its way out. Another possibility is simply a loose belt. Easy to check the latter.

Autozone or Advance Auto can check both the battery and alternator at the same time, right on the vehicle! 

It's your alternator.