You asked about an "HVAC control switch E1AH-19D961". Please read How To Decode Ford Part Numbers as you read the # off the part, probably expecting it to be a part number, and then only read part of it.
But according to the cross ref:
E1AH 19D961-AA ID # crosses to Motorcraft # YH-379 which is part # E1AZ 19B888-A
E1AH 19D961-BA ID # crosses to Motorcraft # YH-380 which is part # E1AZ 198BBB-A
You can look those part numbers up on the page at Documentation/HVAC/HVAC Systems.
Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.