Hello I have a 99 blazer with 4button 4wd. 4wd was working good last night during the snow storm but this morning nothing. The 4hi light just blinks, I can hear the encoder motor, and the actuator. The encoder only makes a nose real quick when trying to go into 4hi but it is longer when going back 2hi. Question is do you think the encoder is bad? I'm not sure how long it is supposed to run when switching to 4hi. I'm not getting any codes. Thank you

 

Damn, man you got good ears if you can here the actuator under the battery moving. You need to pull the battery and tray and attach a vacuum gauge to the hose to the actuator. Should be holding around 15 in. steady at idle. You'll of course have to temp re-install battery to start it to test. A bit of a PITA to do but will eliminates a number of causes for no 4wd.
The TC motors do go bad, but a lot are unnecessarily replaced because something cheaper and simpler was the culprit. Usually vacuum related. Most common one is simply a hose is cracked or came loose where they all meet below the master cylinder. The hose to the hidden vacuum reservoir likes to come off.
If you do replace the encoder motor DO NOT "test" the new one off the vehicle. That ruins them.

 

I will pull the battery today but it's -4 right now so we shall see.

 

I feel you. it's -9 here right now. Supposed to warm up Sunday thru Wednesday into the 30's and low 40's. Friggin heat wave.

 

I was hoping it is a ice issue, being it happened during the storm. There is a lot of snow and ice under the truck in the area of the of the front diff, but not alot near the tc. Hopefully the warm spell coming will help me out

 

check for vacuum at the switch on the firewall around the distributor, Ive seen this fail and act like yours.