The Blend door actuator is a motor driven positioner, a dc motor controls direction and the gearing to a potiemeter provides position feedback, to the climate control module.

To test the system if your blows just hot or just cold all the time, do the following.
If yours system blows cold.
1. start car, let engine warm up, turn on heat full, and Fan full on,
open fuse panel and remove "HVAC" fuse 10 a, fan stops.
Replace fuse, fan runs again and the temp of the air should go hot, if so that means the blend door is not stuck and the actuator moved, if the temp of the air goes cold in 10 to 12 seconds, the actuator is lost "no position feedback" and does not know the position of the actuator, the reason the actuator travels full hot and then cold, is because after power down and then power up it tries to find the home position but can't so it defaults to one of the full travel positons full closed "cold" or full open "hot".

2. Mine is cold so do the procedure above and when its blowing hot pull the ful again before it goes cold and remove the plug from the actuator motor before its commanded to close and go cold again.

Good Luck

I have a 1998 Bravada with a blend door actuator problem. After following JBAG's post I found it very helpful. After looking over the issue I would like to add the following. I found no need to disconnect the vacume line as to avoid snapping it like the previous poster. With the vehicle running I moved the position selector to determin what position would leave the vacume arm with the least tension before "gently" prying the vacume pump up and off. For my vehicle it was in the vent position. With out the arm having tension on it the vacume pump will come off easier. Once the pump was pried off (up). I again moved the position selector and found the position that extended the vac. pump arm the farthest. This allowed it to flex easier when moving it forward out of the way over the plastic mount tabs. My suggstion for removing the two actuator screws is that don't rule out using a 7/32 open and box end mini wrench. I also would recomend a 1/4 drive with a "flex head" or 1/4" stubby. Hope this helps and again thankyou JBAG for pointing me in the right direction.

Follow up to my previous post. Make sure you again move the position selector to your previously determined slack postion when reinstalling the vacume pump and then follow the instructions for recalibration.

Goodluck,
RJF

Thanks for the posts that put me on the right track with a blend door actuator problem on a 1998 Olds Bravada. Now that I have done it I have several improvenents on doing this job. Look to previous posts for location and access to the BDA. As previously stated you will need a 7/32 1/4 drive and I would also have a 7/32 mini wrench open and closed end available. First I did not disconnect the vacume line to the vacume pump so as to not risk breaking the mini inlet nozzle, hose or fitting.. there is enough hose to work with when removing and swinging pump out of the way. Then I found that I needed to start the car, and find the right position on the air direction control knob so that there would be NO tension on the vacume control arm before gently prying up the the vacume pump to get it out of the way and have access to the blend door actuator in my case a (Dorman #604-106 for an auto climate control application). On my Bravada putting the direction control to "vent" relieved tension on the vac pump via control arm. Turn engine off. Once the vacume pump is pried up/off I again started the car and changed the direction flow knob once again as to give me the max arm extension off the vac pump arm. Why? so with the arm on the vac pump extended it would flex easier when having to swing the Vac pump over it's original tab mount swinging it toward you and to the left out of the way. Work slowly and methidically as to not break the tab at the end of the vac pump arm attached to the direction flow flap. This means the vac pump will remain connected to the direction flow door tab. Don't use a 1/4" straight ratchet drive but use a 1/4" "flex head" drive ratchet. There will come a point where the ratchet will not ratchet any more. You can then use the the 7/32 mini wrench or if having small hands, like me, was able to put the socket alone on the first of two screws that need to be removed and removed them the rest of the way by hand. Having a handle magnet available to retrieve the screw if you drop it is advised. Ok once the two front screws are removed, gently pry up the actuator to remove. Check pin configuration on your old actuator and your new actuator. "I believe" the auto units are 5 pin and the non-auto are 4 pins. OK now with the actuator removed feel your way up to the blend door stem and turn it open and closed to make sure it turns freely. Make sure your car is turned off and NEVER put any power to the new BDA before total installation and tightening. Pay attention to the location of the keying on the new BDA and the location of the keying on the BD itself. It will be a neutral position. Look at the BDA and then aligning the BD itself to a similar position as best you can. A little playing with the alignment will be necessary. You know you got it right when the BDA drops dn on the screw hole mounts. After the 2 screws are tightened you can connect the wiring plug to the BDA. Now gently slide the vac pump up, over and forward to get it in postion to remount. STOP, now start car and return direction flow knob to the original no tension postion, on my (98 Bravada) the "vent" position. Stop car and then remount vac pump. You should be good to go. On inspecting my old BDA, as previously found by others, discovered the main drive gear cracked.

Good Luck,
RJFENT

I have a 97 Bravada with same symptoms as some on this thread. Heater core is shot and actuator is broke. I have the new heater core ready to go in and a replacement actuator. According to GM and every other parts house, I have the correct replacement actuator. (the part number has changed from 16124922 to 89018356)
Now here comes the tricky part. The old actuator has six pins numbered right to left 5 to 10. So does the new part. The old part used pins 5, 7, 8 & 10. The new part has pins 5 & 6 removed. Does anyone know how I should rewire the plug so the correct wires are in the right spot? The control on the dash is a simple red/blue temp knob.
Thanks for any advice.

I personally would not be trying to re-wire the blend door wiring harness. The pin configuration should be based on whether you have a manual or automatic heater controls. Look for Dorman to save money, probably half of a GM price. The BDA for auto climate control will be much more then the BDA for a manual contol set up. I don't remember seeing manual controls on a Bravadas but that is mostly in 1998-2001.

Read nightskyrider's thread again and have a question. What is shot about your heater core? Is it leaking or plugged. when I got my 1998 Bravada it had no heat. There was two reasons for me. Blend door actuator and plugged heater core. Literally took ten minutes to unplug heater core. With Bravada at operating temp., feel both hoses going to heater core. If one is hot and the other is not then there is no flow through core. I slid the hoses off and connected a garden hose and back flushed it. Cleared right up. Might even consider runnning some radiator clean chemicals in the core and let it set. I then carefully cleared the water out with my air compressor. When the core is dry I added via funnel fresh Dex cool until it ran out other side and then put hoses back on. The problem with most of these 4.3s using the red dex cool is two fold. First anytime you have one of these you need to replace the rad. cap with a Slant 10230 or a Slant 11230. Second fill your resevoir to the "hot" level when "cold" The Dex-cool gels and clogs form contaminates and air infiltration