Okay, how is this wording?
The bathroom fan/light works fine. However, I'd like to turn the switch on and have the light and fan come on as usual. Then upon leaving I'd like to close/shut the switch and have the light go off and the fan stay on for another…maybe 15-20-minutes.
What parts do I need to keep the fan on?
Thanks,
Randy
USA-MA
[email protected]

Your post is a little confusing. I've been doing something similar for at least 30 years.
The fan is a combination IR lamp/fan and exhaust.

The fan and light are both separately controlled with independent switches. The IR lamp is controlled via a mechanical timer.

When the fan is turned off, the fan will not go off for 20 minutes. I used a delay on break timer from ABB SSAC Timers & Controls Fast Facts (800) 377-SSAC(7722).

I can't quite determine exactly what you want.

I agree with Kiss on the Mechanical timer, They are easy, quick operation, and cheap solution. If you want the Fan to continue to run 15 minutes Every time, even if for a moment, a Delay Off relay will work fine and is adjustable.
Electronic timers may take extra steps.
Kiss, did that number work?
handyrandy, not trying to piss you off, just trying to provide a solution.
Take Care, Randy