Defroster blowing when turning key on
A couple of days ago, I went to start my truck and when I turned the key on to wait for the glow plus to go out the defroster blower/motor was on high. I have the climate control and it was turned off. I turned the key off and back on, but the blower kept blowing on high. Once the truck started, I turned the AC on and the AC blew out the vents like normal and the defroster stopped. The truck still does this now after several times of stopping and starting.
I did some google searching saw possbile vacuum issues. Below is what I checked. I did not want to do more without checking with you guys because I know some of you all know what the heck you all are talking about.
What I did:
Pulled all 3 electrical connections, 1 at a time that is connected to the vacuum pump and it had no effect.
Pulled the small hoses that are connected to the vacuum pump, 1 at a time and not difference.
I do hear the shift on the fly 4x4 engaging/disengaging each time, so that appears to be working. It comes on each time I try it even while I testing the electrical and vacuum connections.
What is my next step? Do I by a vacuum gauge tester and go that route, or take it to the shop? I am not a mechanic, but can do minor stuff? I decided not to start tracing the vacuum lines before posting here and checking in with you all.
Thanks in advance.