I have never heard of aftermarket HVAC controllers.

You could goto a junkyard and pull out the whole manual HVAC system.

Otherwise, I think you might be stuck with a new programmer.

But first, find out what the PCM is seeing.

Update: Ac Clutch-Low Voltage code..Intermittent problem found...Clutch often not engaging..it is now fixed !!
Ya this was a total fluke that I found out what was wrong....
The green wire that comes off the AC clutch connector that travels through the split loom tubing had been damaged, and when I accidentally squeezed the split loom tubing the Ac clutch then engaged.
So with a bit of cutting & rewire & solder with heat shrink tubing, all is back working normally.
The AC tech on this one really believed that the programmer was resonsible, I am so glad this was a simple fix.
Thanks for all the input from all the members! Nice to have Ac for the summer now.

Another Update: After repair of wire inside split loom tubing, the AC compressor stopped working again. So while car running, I jiggled the connector going into the AC clutch and was not sure if the connector or clutch coil is burnt. I had a shop that was able to power in another connector wired to the battery, and the coil is fine, but my clutch female input connector wire/ pigtail is toast.
Most local shops said the connector was not available. I found Delco does make connector with wires and and part # is PT209 or 12101937
http://www.autopartstomorrow.com/par...-delco-product
Hope this truly fixes my AC electrical power input problem.
Will know this weekend , once installed.

Do You Think The Old AC Clutch wires were fubar? Wow.. after removal from wire loom!

The new wires needed new small split loom tubing, otherwise would have been against the hot rad hose.
Also I did not use the clip that held the entire thick wire loom way close to exhaust etc!
It now sits away from all the hot zone with a good air gap now.

AC now is finally repaired and all is well as the humidity hit 100% today ! Perfect~!

Oh and this is how the new AC Clutch PigTail presents itself inside Delco Packaging.
No fusible link here. Who ever previously did this repair was too cheap to buy a new connector or did not know a new one was available?

No, that is not a fuseable link. It'* a diode to prevent current coming back up the wires. I guess the compressor is capable of putting out some power when not in use. but, why its not included on the new harness is beyond me. Just connect the new connector to the diode.

Thanks Mike Re Diode.
Is it really necessary to have a diode in line?
Is it potentially dangerous to run without one, as it is now?

Did some reading...
Ya I guess I better get a diode back into this system. It protects during the period of the clutch re-cycling of over 100 volts from magnet getting back up into the ECM. Why would Delco not make colour coded new harness and not provide a new diode is beyond me.
Ok so it is into GM on Tuesday morning and hope for a new diode, as I really do not want to re use the old one and really have no clue how to rewire this mess with the old one anyways. It does appear that a new diode is available supposedly with X & Y one wire coming out of each end? Somehow I think it has two on each end and am going to need a specific diagram for installation.
http://www.4s.com/Upload/Four%20Seas...STALLATION.PDF
Good God this is a mess.
Anyone got a wiring diagram with the AC clutch diode wiring diagram from a 97 Park Ave?

Sure do!!! I have an Alldata subscription for my 97 and from the looks of the schematic, it also covers your Buick also.

Thanks Mike. I also found this one schematic that does show diode going between green & black wires.

The Delco PT748 diode does indeed have two wires in & out. Makes sense as you have to have a bridge of current flowing from connector into diode and then back out. You then have have protected flow out on the other 2 wires. I hope I can obtain the correct install info from GM or a tech to cnfirm correct installation once I have the correct diode also to be confirmed by GM.

If any one has installed this diode and knows how to install.... fill me in please!