I have multiple issues right now with my 99 s-10 Blazer LT 4X4.

The most annoying one is my heater. The issue is when I turn it on, no matter the fan speed or setting, it will blow out from all the vents, floor and dash and also windshield blower. It also does not allow me to change the temp. What it does is blow hot for a few seconds then blows cold for a few seconds and when it goes back to hot i have an annoying squeak sound in my dash. Any Idea what I can check or look into to try and fix this???? Winter is right around the corner and I need my heat.

Second, it will not let me switch it into 4WD. If i hit the button like I have a million times before, it just blinks for about 30 seconds then go back into 2WD. I have no idea what to do about this.

Third. I have a very loud whinny noise coming from my rear end when I let off the gas. I'm thinking barrings but not 100% on this.

any help would be great. thanks

 

https://blazerforum.com/forum/tech-a...ill-help-7180/

https://blazerforum.com/forum/tech-a...acement-29981/

These are both from the DIY section on the homepage. There is a lot of good stuff there along with an alternate blend door replacement.
Your whinny noise could be a whole bunch of stuff but most importantly you need to check for oil in the rear differential and your U -joints

 

Does the vehicle have manual HVAC:



Or does it have Automatic Climate Control:

 

On the rear squeak it may be as simple as the dust shields rusting and rubbing on the rotors.

 

I have the top one the HVAC


And thanks for the responses, I will start looking at those threads right now

 

hey man thanks a lot for the link, I was able to locate a broken hose on my vacuum line, fixed both my heater and 4WD