1998 GMC C1500 Heater blower and indicator lights.

Purchased used my 98 GMC Sierra 1500 4x4 ext cab short box. The blower only worked on high not any other setting and only came on at the time you started the vehicle only the hottest air came out no matter the setting. The brake light indicator and anti-lock indicator lights go on and of as you turn the switch to the blower and the cruise control worked once and now not at all.
I replaced the heater control board the
complete dash assembly to the heater system the fan blower relay and the air door actuator now the fan turns on and off sometimes but still only on high and I now can control the heat.
I am good with this type of work but this one has me stumped, I read an article about checking the two wires that go to the blower something about they can get brittle and short out, I checked that as well they are fine. Any information would be awesome, Thanks.

Ok I replaced the as per your request and still have the problem the fan works only in the high position
what else could it be?