The Key / Lights Buzzer and the Lights On Warning Relay are in the lower center of the dash, just to the right of the radio. You can reach them through the glovebox openning, or from above if you have the dash pad off.
Thanks for clearing this up for me. I was looking at the Osborne 70 Mustang electrical assembly manual (page 51 if you have it) and it shows a relay in the right side cowl. This is in addition to the buzzer and relay behind the radio. It calls out D0VB-14C690-A Relay Assy.
I looked all through the L-M MPC and couldn’t find any relay with a part number close to the number you provided ( the number D0VB-14C690-A is an engineering # and as such may or may not be close to the actual part number ). Since it is a Lincoln number, I suspect a power seat back release relay ?
Does your Cougar have this option ?