I have read through many of the threads pertaining to this issue and have not come up with an answer. I was wondering if there is a good way to find out of your door actuator is bad or the plastic pin that attached to the blend door is cracked. I do have vacuum to the actuator so I believe that rules out vacuum problems. It seems that the white plastic piece that goes into the air box is pretty loose and there is a good amount of sideways movement(like it's not connected tight inside the air box). I haven't been able tomove byhandthat plastic piece to get the door to moveand get heat on the floor. Has anyone had experience with this or a good rule of thumb to go by?

Thanks!

98 Blazer 4x4 4.3L 155000 mi

 

I would start by measuring the amount of vacuum that you have at the actuator itself. Compare that value with what you get at the motor. There should be a small difference, but not much. If it drops by half or more to the actuator, you have a vacuum supply or HVAC control head problem.

If the vacuum checks out on both of the lines in the appropriate modes, then the problem could be either the pin, the door itself, or the diaphram in the actuator. To test the actuator, you can pull a vacuum on one side and it should hold steady. If it drops or you are unable to pull a vacuum, you have a faulty actuator. If, when you pull a vacuum, it takes more vacuum to move the actuator than what is supplied, the door may be hung up or other wise obstructed.

*EDIT* For sake of repetition (well, really cause I couldn't find them in a cursory search), here are the vacuum diagrams and charts for both Auto & Manual climate controls found on the '98+ trucks:

AUTO:


MANUAL:

 

I have a 1998 Blazer 4x4 with exact same problem. I put a little mirror inside the duct. The rod thatthe floor vent door pivots on is broken. The actuator connects to this rod on the outside of the duct. I understand this is quite a job to fix. The whole dash has to be removed. And the air box has to be split to gain access to the door. I was going to attempt to fix mine, but a broken hand kept me from doing so. I'll attempt again this spring.

 

I tried the mirror trick to but I couldn't get a good angle to see anything. What kind or mirror did you use?

 

Does anyone have the part number for the floor heat diverter flap. Mine is indeed cracked. Or do I have tobuy the entire HVAC housing as one unit which inludes that door?

 

By the way I did get this fixed without tearing apart the dash. Just a little cutting of the lower ductwas needed to get the door out replaced and back in. Of course you need to patch the hole as you see fit.I did some inspection of the actuator and it seems thatit pulls down to far which puts stress on the door and bends it. With the hole in the lower duct I was able to watch the actuator and the door open and close and that's when I noticed the actuator still trying to pull down even though it's closed shut. Eventually the plastic gets tobrittle and that pressure eventually cracks it. I wonder if most doors break around the 9-10 year time span.

 

I know that this is somewhat of an old post, but is there some way that you (TheJuicer) could post a few pics of exactly how you changed the door without tearing the dash apart?

Even a little bit better step-by step description would be OK as well. Mine is broken as well, and I don't mind "patching" the ductwork after cutting it a little. The knee bolster and covers are in good shape, and it wouldn't be seen anyway...

Thanks,

HCII

 

this post describes a quick fix for the "damper" breaking and preventing floor setting from working.

anyone know what was done and how? i am looking to fix this issue before winter, i dont want to freeze my feet off again.

thanks all.

 

Hey guys I will see if can get some pictures up and a better description of what I did. It's not an exact science and I am not sure if it was more luck that I didn't ruin the hole where the blend door comes out of the dash. That would have ruined any chances of it working properly. By the way the only issues I have had since is that my duct tape patch job was more temporary and fell off as it dried up. I was scared my "fix" finally broke down but I have since used plastic from a milk gallon jug and cut it to size and glued it. Hoping that will last longer.

 

you may have some of the most wanted pics on this forum that can cure cold feet.

cant wait to see them.

thanks