1st I'd like to thank everyone who contributed to the thread linked below as it was my guide to solving the issue of no airflow to the floor of my 2000 Blazer -

https://blazerforum.com/forum/2nd-ge...or-heat-17808/

In my case I too had airflow to the defroster & dash vents but absolutely no airflow coming from the floor vents. I had replaced all of my vacuum lines in the engine compartment as they were rotted & cracked.

Then I began by removing the center console and lower kick plates at the bottom of the dash. After disconnecting the battery I removed the computer and it's mount (right on top of the transmission tunnel in front of the airbox). This will expose the lower portion of the airbox so that a hole can be made to replace the windshield defroster valve (#21, highlighted greenin the image below) -




I decided to use a hot knife to make make the opening in the airbox - map gas makes the knife blade hot fast -



The rough opening -



I reached in and removed the broken valve. I had to pull on the white actuator lever (#20 highlighted red in the diagram) to get the broken piece of the shaft out -



Looking up into the airbox



Fortunately for me there was a dealer in town that had the valve in stock - old & new -



Here are a few pics of the actuator lever - the valve shaft can only be inserted one way as it is keyed -






Here is an end view of the valve shaft that goes into the lever -



The other valve will droop down as vacuum is depleted but I just worked with my hand under it. Getting the new valve into place was easy on the actuator side, just insert it into the airbox hole. Getting the other end of the shaft into it's hole took some more doing but it is shaped so that it can be pressed into place. Once the valve was in place I placed the actuator lever onto the vacuum actuator arm and then pressed it onto the shaft of the valve with a happy click. Then I installed the return spring. a pic of the final assembly -



Then I reconnected the computer, the battery and started up the engine to see if everything worked- yes!. I taped up the opening temporarily to make sure that the airflow went to the right places -



After a good test I needed to put the cutout back in place and I used some common strapping to make attachments -




and attached a few small pieces with small 1/2" screws - (areas on the edges roughed up to better hold the adhesive) -



After trimming the straps back some I attached the cutout to the airbox and sealed the opening with some blue silicone RTV-




Then I installed all of the trim pieces and center console and it works like it supposed to.

GM Part numbers

Valve - 52470781
White Actuator Lever if needed - 52487574

Thanks again to the original authors!

 

Good write up!

 

Nicely done! Thanks for sharing.

 

Nice. Looks good, good job