My 98 Blazer keeps blowing the ATC fuse when I try to switch out of 4hi or 4lo. I cleaned all the connections on the TCCM. What else could it be?

 

if you have extended needle nose you can go in from the front by pulling the 2 headlight clips pull the lite forward let it hang use a flash-lite and pick a hole, be cautious of damaging your new rubber diaphragm. did you put your transfer case vacuum switch down as far as the original one?

 

just fyi I found a hole in the new actuator that I just bought on friday. Obviously that part is no good, so I'll take that back tomorrow and get another one and see whats going on there. As a side note, Ill add another T fitting in the mix and plug in the reserve ball and see what that does. I took the check valve out and put in a standard T fitting and now my heater control changes from defrost to floor etc...

 

The check valve might have just been installed backwards. The check valve should be the first thing in that line, then it should T off into the HVAC, 4wd, and vacuum reservoir.