2000 cougar headlight fuse blows

Hello all I have a 2000 mercury cougar with 34k on it. About 2 months ago I turned the lights on and nothing happened. Since then I have had 4 different mechanics with electrical knowledge look at it. The #26 fuse keeps blowing which controls the the headlights. It's on the top row 3rd from the right 7.5 amp. I replaced the fuse box and the lights worked for 2 weeks and it started again blowing fuses. The last mechanic was VERY knowledgable about auto electric. He did an HID light conversion with a relay which completely changed the system to upgraded lights (masterful job I might ad). That didn't work the fuse blew right after the installation. Then he did the TSB modification ( pita fix) or pain in the arse if you don't get the pita because the alternator is under the car on the right side very difficult to work on. That didn't work it still blows fuses even without driving just by turning on the light switch. I havn't replaced the alternator and after reading this forum that didn't seem to help. Havn't replaced the light switch ( ford doesn't have a new one available nationally I checked) Maybe aftermarket is available. Part #XS8Z11654BA. That wire assembly for the Alternator is my next step Part #3U2Z 14S411 SHA. Will let this forum know the results.