I noticed today when I turned the a/c on, there is a pretty fast ticking sound. When I turn the a/c off, the tick goes away. Any idea what part needs replaced?

2002 LS
2WD 4D
72k miles

 

Is the sound coming from the dash area or from the engine area?

 

Engine area

 

Possibly low refrigerant level causing the compressor to cycle rapidly.

 

Try recharging your AC unit. Mine ticked from the engine bay even though the AC was still cold. I recharged it with one of those cans with the little gauge on it found at an auto parts store. It has fixed my problem so far.

 

I have a new A/C compressor on mine & it does the same thing. I just drive mine The A/C is cold & to specs. These Blazer make all kinds of different noises. More than our Jeep, or the Lumina we owned or the six Fords we have owned. If you worry about most of them you will be driven crazy. Ours has been knocking, rattling, clunking, & etc. For 33,000 miles now it just keeps running. My wife commutes a few times a week 120 miles round trip to work with it. We did a bunch of off-roading this summer, where we were sometimes 75 miles from the nearest town with NO cell service, & this Blazer just kept on trucking & never left us walking.

 

I'll try the recharge. Not sure if I will do it this year or wait until next year. Actually, I'm due for an oil change so maybe I will have my mechanic check it out and at least get it diagnosed.

At 72k miles, this is a new noise. And this ride is still smooth and quiet. My other vehicle is a Honda, and I have to say the Blazer handles better, quiter, and much less rattles.

FYI - I have not done any a/c maintenance since new.