Nathan Young wrote:

Where is the RFI capacitor typically located in a 1971 Piper Cherokee 180?

On the firewall? In the cabin? Next to the battery?

Here's a link to the Cherokee electrical schematic.
http://www.needlescentered.com/cherokee_electrical.htm

Thanks,
Nathan
On the alternator.

What kind of RFI are you experiencing?

Things that cause RFI in GA airplanes:
Brush arcing in electric Turn Coord.
Brush arcing inside the alternator.
Brush noise in electric motor (such as old rotating beacons)
Bad shields on spark wires
Bad shields on P-leads
Bad shields on strobe wiring

MikeM