Weird idle. 94 Camry 4 Cyl

I have a 94 Camry 4 Cyl, when I start the car, and let it idle, it'll be fine for about 10 seconds, then for about 4 seconds the RPM drop a little bit and the lights dim, then it'll have 10 seconds of normal, then 4 seconds of dim, and it does this over and over and over and over. The RPMs drop just enough for me to notice the needle move, it doesn't seem to be anything significant. I am just wondering if this is normal or a sign of impending doom?

Is that all the time or only when the A/C is on? My wifes 93 does the same thing when the A/C compressor kicks on.

Is that all the time or only when the A/C is on? My wifes 93 does the same thing when the A/C compressor kicks on.

I was thinking that too, I'll have to check, I don't believe I had the AC on, but it may have been an oversight, haha, thanks :)

The defroster will kick in the compressor also.