92-94 Burb heater AC controls

[Robyn]

Well I replaced the AC compressor and recharged the system on the 94 Burb and all went well.
About an hour later the heater starts making a thunk thunk thunk noise that wont stop even with the ignition switch off.
After some investigation I discover its the recirculation door motor that is not stopping but instead jumping a cog internally.
I fiddled around under the heater and was able to unplug the wires going to the little motor after I got the thing set to recirc.

I poured over the manual and finally found reference to the thing.
It says that the door motor should recieve power for 22 seconds and then turn off.
Mine stays on continuous now.
It would seem that the magic control panel setup has taken a poop.

Anyone having had anything to do with these older systems please let me know.
I have found some "Good used units" yeah right, but want to collaborate my findings before spending the $$$$.

The service book is a tad vague in this area.
Any input would be great

Thanks

Robyn

[diesel65]

Hi Robyn,
I have replaced a few recirc actuators in the 94's, when you get that thunk, thunk, thunk when you shut the ignition off.
The GM manual instructs you to roll back the dash to replace the actuator, I get in there with a 1/4" air rachet, a stubby extension and a Snap-On flex socket, I don't remember if it was 5.5 or 7 mm. The upper screw is not visible, you need to do it by feel and guess work to aim the socket.

[Robyn]

I think the actuator is fine, its seems that the power is not shuting off from the controller???

The actuator will run either direction and do so happily.
Now tell me this, does the actuator have a switch inside that opens once the unit reaches the limit of travel??

If this be the case then maybe I need to replace the actuator.

Right now I have the unit set in the recirc position and the wires unplugged.

let me know on this

Thanks

Robyn

[Robyn]

Im supprised that you can even get any tools up in between the firewall and the heater box its so close. The other two actuators are a little easier for sure

[diesel65]

The early actuators did not have feedback circuits, I do not know how the controller knows where the the door is, I think that the controller commands the actuator to one side and it applies voltage long enough for it to think that the door should be in a home position, but if the door reaches home before the controller times out, the actuator will just stall like a power window motor.
The thumping is when the door is at home position but the actuator did not stall.
I can only tell you from experience that when I heard a recirc door actuator starts thumping, I just go and replace the actuator.

"Im supprised that you can even get any tools up in between the firewall and the heater box its so close."

That is why GM will tell you to roll the dash back.

[Robyn]

Personally I dont see what good that would do. The access seems to be only from the bottom side between the firewall and the unit.

Mine would just sit and do the thump thing for a long time. The circuit is supposed to shut off in 22 seconds but the thing had power for much longer even with the ignition shut off.
I was thinking that the control module in the dash had gone south???

[Robyn]

Well I fooled around with this thing some more yesterday morning.
I also read a few articles online about the HVAC system on those critters.

I found that my controller is fine and is doing just what its supposed to do.

Its just as you mentioned, the motor is gunny sack.
It skips a cog only when going to the recirc side and then stops doing it when the controller times out.

Sure seems wierd why they stall the motor at the end and then wait for the power to cut off.

Must be all about $$$$ for the initial build.

Tried to get the motor off but the top rear bolt is going to be a bitch.
I also need to get a really good source of light and a mirror so I can pinpoint the top bolts location.
Also looks like the sound deadening materrial is going to need to be trimmed slightly to allow my tools to get in there as well a let the motor slide off the shaft.

Thanks to the replies.

Robyn

[diesel65]

Like I said "do it by feel and guess where to aim the socket". The 1/4 inch air rachet makes it much easier to spin out that screw when you get lucky enough to mate the socket.
Use a flex socket because a socket with a seperate universal is too deep.
After you remove both screws the actuator just comes off the shaft.
Lots of Luck and don't be afraid to curse............lol

[Robyn]

OOOOOOOOOOOOOOOOOK
Well my mouth usually needs a liberal rinsing with listerine after working on the rigs anyway. :D

For the moment I am just ignoring the little beast and let it do its thing for 20 seconds and when it no longer will swap the door flap then I'll get out the tools (And the mouth wash) and have at it again
I need to find a good actuator. GM wants $60 for a new one. :eek:

I do want to fix it though. Maybe I will wait untill I have a fresh one and can see where the screw is located on the top side and that will make life far easiler than poking in the dark.

Seems like its always something :rolleyes:

Thanks

Robyn

[jggiedeman]

Robyn,

Did you ever change the recirc motor out? This is happening to mine. I believe I'm going to remove the dash so I can clean the rest of the interior up.

Jerry