I had similar on my '05 FXD with 50k miles on it. Starting cold, the oil light went off as it should. Riding around the oil light was off, correctly. But after the engine was warm, at tickover, the oil light started flickering on. Or after a ride, when the engine dropped to idle speed, the light flickered. Blipping the throttle made it go out.

Eventually got to the stage where it was on anytime at tickover, hot or cold.

We stripped the camside out. The outer tensioner was 1/2 worn, but the inner had started wearing grooves in the pivot. Don't assume, if your outer is fine, that the inner is too. Get a dental mirror, the smallest you can, and peer into the cam chest to look at the inner. The oil pump was scored, and the pressure switch looked like it was rusty. Being stainless, this couldn't be the case, obviously, and a wipe with a rag showed lots of minuscule bits of orange tensioner all over it. The flickering oil light had been caused by it not being able to drop back properly as the revs dropped.

Fitted a high pressure, high throughput pump, replaced the tensioners, the cams were fine so stuck them back in.

Don't delay, check those tensioners.

 

Using the wrong weight (too thin) oil could do it.

 

What weight oil did you use when you changed your oil?

 

+1 on thin oil, but still check tensioners as a precaution

 

I've seen tensioners last to 50k, almost completely gone at 20k, and a grenaded cam chest at 31k, so dont assume the spring loaded tensioners are ok just by what you read here. And its the inner tensioner that gets all the wear.

baff hit it in the money as to why your light is flickering. Theres crud built up in the pressure relief valve in the cam plate, and that crud comes from either the tensioners or from coking. You need to go in to find out which.

Dont wait till your motor is running strange before you check it out. Do it now and upgrade to the SE cam plate or one of the aftermarket ones with hydraulic tensioners