Hi, I am new to the Blazer Forum. I just bought a 2003 Blazer LS. Here's my problems; 1) After about 15 min, the amount of air flow from the a/c drops dramatically. 2) a clicking or knocking noise comes from the area of the right front wheel after about 15 min. of driving--I have a feeling that it is a problem with the vacuum lines and not just one, but two areas. Where and how should I start diagnosing the problems and could a leak in the vent flap actuator cause the 4x4 actuator to act up, or vice versa. Any help would be great. I am a DIYer--Thanks.

 

Sounds like you might have an issue with the Vacuum switch on the Transfer Case. If that Switch is stuck in the open position. it might steal vacuum from the Venting and engage the Actuator.
Another nortorious issue with these Blazers is the small vacuum hose that is on theh drivers side, under the hood, just behind the ABS system. The small hose come off a small black Tank that is literally in between teh inner fender well and outside fender. Look for a 8" hose that comes off a Tee in that area. if the hose is going nowhere, that is a problem.

 

I changed the vacuum tubing coming from the intake. I will check behind the dash for more leaks (I can hear a hiss when I switch vents).