No heat before & after thermostat change
 

I woke up this morning to 25 degrees and noticed I had no heat out of the blower. Both the gauge temp and Scangauge digital display showed the engine up to temperature between 188 and 198. I tried switching different vent and temperature settings. I felt the upper radiator hose and it felt a bit soft. Not sure what it could be, so I changed the thermostat, thinking even though the Blazer is at operating temp maybe this could fix it.

After changing the thermostat, running to operating temperature with the radiator cap off to remove any air and then topping off with coolant I still have no heat. Both heater hoses are hot, with the left hose (one going near the t-stat) being a bit hotter.
With the radiator cap off I can squeeze both heater hoses, upper and lower radiator hoses and push water out of the top of the radiator, so I'm not sure if its a flow problem.

I also noticed that with the forward dash vent selected it blows cold air and when I switch to the window defrost vent it blows slightly warmer air, not very warm though, maybe 55-65 degrees. I cycled through all vent, fan speed and temperature selections several times.
Any ideas?

sounds like the blend door, or the blend door motor are NFG.
you can check to see if the blend door motor is working by one of two ways.
1. you can turn the key ON, engine OFF. wait for everything to shut up and quick beeping. turn the radio off, and close the doors. when its nice and quiet, turn the TEMP knob from hot to cold, or cold to hot. either way will work. if you listen VERY carefully, you should hear a little electric motor make some noise. if you do, you want to pay attention and see if at any point it sounds like the motor starts to struggle.

2. you can pull the glove box down, make sure that you empty it first. when you have the glove box down, get a flash light and look over to the left a little bit and on top of the air box you will see the blend door motor. since you're already on the passenger side, take your right hand and stuff it under the dash, reaching for the motor. when you get your hand on top of the motor, you should feel a little ridge in it that is round. you might also be able to see it with the flash light. that little white ridge is the axle that the blend door locates to. so with your right had on that, so you can feel it move, with your left had, turn the TEMP knob again. if you feel it move, then you are in luck. if you dont, then you need a motor.

if you try the first method and it sounds like the motor get resistance some where along the change, then go to step two. if its too loud where you try this, go to step two.
there are (2) 7mm bolts that hold that motor on. you should be able to see both of them. there is NOT one in the back. there is only a post that is located in the back that the motor uses. if you have the right tools, you can take that motor off without having to pull the dash down. if the blend door is getting stuck at any part during its travel swing, you might be able to get the motor off and then grab the axle on the door and swing it back and forth to clear the obstruction. just do it slowly, you never know what it could be. it might even be a pencil. ive seen stranger things.

I can hear the motor when I turn the temp knob and its not too loud. However I'm not sure if this is normal operaton but the motor only makes noise for five clicks from hot towards cold. After the fifth click or notch at the knob I hear no more movement from the motor.

Also I put the glove box down and can see the vent positon motor but I'm not sure where the blend door motor is. Thanks for all the info.

im guessing the motors bad. as long as the hoses are hot,and blower motor blows,nothing else can be it exept a door blender issue.

sounds like the door is either getting stuck, or it is broken. i could be getting stuck. the blend door axle is from the top of the car, to the bottom. the motor sits on the top of it. if you can manage to get the screws out of it, you can grab hold of it and flip it back and forth.
the attached picture shows the motor that you are looking for and the 2 screws that hold it on.
[IMG]https://blazerforum.com/forum/attach...ine=1363306441[/IMG]

Thanks for the info and pic., much appreciated. I did see the motor and screws before and thought that it was the blend door motor, but wasn't sure. Definitely hard to get my hand in there. Maybe my 6 year old could get her hand in there and turn the driver.

Been there done that. It was my blend door, had to pull the dash....not fun!

if you have pulled the dash before and dont think that its that bad, you can go that route and it would make life easy. if you have never done it and dont feel like taking the chance on it, then you have to figure out what you want to do. i have pulled several dash's out of these s-10's so its not a big deal to me. just a bit of work. i will tell you that if you go the dash moving route, you dont actually have to pull the dash out of the truck. you just have to go through almost all the steps so that you can get yourself either behind it or over the top of it. the nice thing about the 98's that i know of, and i think its the same with almost all 2nd gen, is that when you are getting close, you can just set the dash on the passenger side seat and you get to the air box and do what you need to do.

keep us posted.