no floor heat

Trying to find the vacuum ball for a 98 blazer LS. Heat is only coming through the defrost, and toes are getting cold

should be in the engine compartment.

Round black ball the size of a grapefruit.

should be in the engine compartment.

Round black ball the size of a grapefruit.
Is it possible my truck doesn't have one?

They have the HVAC balls. Follow the vacuum lines coming off of the engine.

should be in the engine compartment.

Round black ball the size of a grapefruit.


Actually, I think that is incorrect....

If it is like my 99 LS it is located behind a flat panel located on the driver side near the hinge. To remove you have to remove the brake modulator valve and two screws and the panel comes off....behind the panel is a square shaped box attached to panel..hence the vaccum reservoir for the HVAC.

But what I think you need is located near the glove box. Check out this thread http://www.automotiveforums.com/vbulletin/showthread.php?t=353328&highlight=floor+heat

Start engine.
Turn selector to Heater. Fan to low. radio off.
Put ear next to the heat/AC/defrost selector and listen for hissing-air sound of vacuum leak. If you hear it...
Take the selector out, unplug the multi-colored hose connector. selector snaps apart into 3 pieces. Put thick Silicone grease around the grooves on the washer and reassemble. Do not plug the grooves or tubes with grease. Use grease thick enough to seal and sticky enough to not be sucked-in to the vacuum source.