I just purchased a 2001 Montero sport but prior I looked at and test drove close to a dozen of them as i was shopping for one. I noticed 3 Montero Sports including the one I bought all the lights flicker at a steady frequency. The one I bought has a minor flicker but noticable especially at idle seems to be dependent of RPM. The others seems to flicker at a constant frequency at any RPM range.

First thing comes to mind might be a alternator issue but wondering if this is a common problem on Montero Sports since I have experienced this on 3 of them. I have done research which no real answer...most common is probably a alternator issue, some of said its a ground issues, fuse issue or even the light/signal which on the column.

I have had vehicles with alternator issues..but never experienced ones with flickering light symptoms.

 

I have a similar problem and I also noticed that when this happens the belt tensioner is moving/bouncing quite a bit. I replaced the Alternator and the 100amps fuse and it fix the flickering issues and it's all good now.