If you don't mind, take a few pictures of the job, we can then make up a write up to help other members.

Im really sorry, I didn't get any pics taken. I was pressed for time to do at it work in the heated shop. In order to change out the actuator I had to do it by feel. It was a real PITA.

I took apart the actuator, and it was the dreaded broken plastic gear that was split.

The heat works now.

That'* OK, we'll get that taken care of at some point.

So it was the cracked gear slipping part of the time inside the actuator that was the problem.

You got it! That is why I could use the screwdriver to coax the arm back over. This new one wont let me do that. So that could be a way to tell if your actuator is bad... if you can gently push the arm over still atatched to the actuator, then the gear is cracked.

Im bringing this back up from the dead. My heat is not blowing hot air.
I took the glovebox liner out, and watched the actuator arm as I cycled from 60 degrees to 90. The arm didn't move at all. So, I stuck a screwdriver in there and tried to physically move it either left or right. Nothing. It was sticc, and I could not move it. That leads me to believe that the actuator I replaced 4 years ago is still good, right?

So now, do I look at the brain box? How do I tell what is going on with this thing? If the actuator cant be coaxed one way or the other, then it must not be getting the right signal? Does that sound correct?

Or, how do I go about diagnosing this thing? I no longer have access to the Tech 2 diagnostic tool I had when I worked for GM.

Thanks for any help, I am sick of freezing my *** off driving this thing!

Depends. Is the outside temperature sensor reading correctly?
Was the car very cold when you were testing it? If so, at 60 deg demand is it possible the control unit would have the blend door buried calling for full heat? and then you move to 90, and it'* still got the blend door buried. I can see that happening if it was 20 deg outside and the car was cold.

I assume because your actuators are so hard to get to in the Bonneville, it'* not possible to disconnect the link to the blend door from the actuator snapon and test to see if the blend door moves? In other words with a hot engine, manually move the blend door to see if you get normal heat. If that happens, then you can diagnose whether your actuator has stuck or failed OR the control head has failed.

Have you checked all the fuses?

It is currently -1 degrees f out. The car was cold. /the outside air temp was reading correctly.

I tried to pop that rod off the actuator, but it wouldnt budge. I didn't want to try too hard and have the damn thing snap off due to the extreme cold MN is experiencing.

The fuses are good. The next time I drive the car I will make sure that the vent level changes direction as it should.. as I seem to recall that the air only went to the floor and the defrost when my programmer went out... I replaced that with a junkyard unit.

I just dug out both old parts I replaced... yeah, I kept the old programmer and the broken actuator. The programmer has soft nipples and the accuator has the broken gear. I wanted to verify again what was wrong the first time and why I did what I did.

Moving forward, I guess the first thing is to verify the air level output. Then, I will check to make sure there is vacuum from the engine while running for the programmer. If that pans out, guess I am pulling off the vacuum line connector to see if these nipples went soft? Or what steps should happen?

When I cycled the hot and cold on the display, that lever didn't move at all. Wo my thinking was either the gear is stripped, or the programmer isn't telling it to move. When I stuck the screwdriver in there, it was firm, and didn't slep. That led me to believe that the gear wasn't broken in the actuator.

So, I tore into the car tonight in freezing temps. Just what I wanted to do. I took out the programmer, and the nipples are hard (literally and figuratively wink wink) so I know the vacuum isn't the issue. I dug deeper and pulled out that actuator. Disassembled it, and the gear is fine! Not cracked nor skipping around like a broken one does. I was baffled. Put all the **** back together, and tested it.
The air still changes direction like it should, cycling through the defrost, middle and floor.
The actuator goes through the full range of motion as the temp is lowered and raised.
While I put it all back together, I let it run to see how it warmed up. After 20 minutes of idling, the car still didn't reach even 180 degrees according to the temp guage. Could this be the problem? Maybe the car isn't warming up??

If this is the case, how do I go through and diagnose to see if the thermostat is stuck open or something? Im really confused with this thing now.

i would put a new thermostat in it, it should get warm faster than that sitting still. its cheap enough to just try it anyway.