Cadillac Repair: 1998 Deville Passenger heat, diagnostic scanner, loose wire

Question
My 1998 Deville will not blow heat on the passenger side.  It will blow hot air defrost and lower heat on driver side, but nothing out of the vents. Pass side will blow only cold (outdoor temp) air on defrost and bottom, nothing out of vents.  Mechanic I have been going to for years says neither wiring diagram he has for 98 or 99 matches what is in my vehicle.  His 98 diagram shows pass control located in dash, when mine is actually on pass door.  Also, I have had heat on pass side twice. Orange indicator light by passenger adjust went on briefly (when heat did work)  Could it just be a short or loose wire? Thanks for any advice!

Answer
I can provide your mechanic with electrical and vacuum schematics of the entire system and my book shows passengers controls on the door. however, without a diagnostic scanner it is going to be extremly difficult to fix and find the problem.

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