Recirc air door problem solution

[RobertGary1]

Many people have reported problems with the recirc door. Sometimes when you press the recirc button the door does not move, similar when you deselect the button. Sometimes the recirc will engage minutes after the button is pressed.
I bought a new actuator from GM. The new one is much stiff than the old. With the old I could grab the recirc door and move it by hand. With the new one it does not move by hand. Sometime internal to the actuator must wear out. The actuator didn't show any wear on the outside that would account for this. In fact the original used a metal gear and the new GM style is plastic.

-Robert

[td1238]

My '99 SL2 actuator uses a plastic gear that is pressed onto the door shaft when the motor is installed. The gear cracked. I'm assuming that the metal one could crack and/or slip, too. Bad design. Would be better if it were merely splined, with matching splining on the damper shaft.

My repair was two small U shaped pieces of metal melted into the gear at the crack, perpendicular to the gear, and with the U facing out. The U will allow for a small amount of stretch, and is opposite to the gear curvature, and so is unlikely to slip out.

So far this has worked for perhaps 1/2 a year. I'm sure that a replacement would work equally well, depending on the route someone wants to go. My repair was cheaper. If it lasts a few years, it might be worth the time (little time).

[RobertGary1]

My problem is internal. I can easily turn the gear on the old actuator on the bench. the new one does not easily turn.

[RobertGary1]

For anyone who just stumbled on this thread because they are having the same problem the take away is this. If you can open and close the recirc door by hand the actuator is broken. I paid $45 at Chevy for the actuator. You may find a good one at a junk yard if the recirc door is good.

[td1238]

If you can move the recirc door by hand with the actuator installed, then yes, the gear is no longer grabbing the door shaft.

I imagine that turning the gear itself to move the motor is somewhat difficult, as the gear ratio is fairly high, and small movement of the gear makes for rather great movement of the motor.

It might also be possible for the small motor gear to slip on its shaft. Worth examining. Clean with acetone and reattach with a drop of super glue if the gear has not split.

...Actually, now that I remember, there are several gears in there. The reduction is quite large. Many drop out of place when the unit is opened. I cannot remember if the motor gear is permanently attached or not.

[RobertGary1]

Its not that it's not grabbing the door shaft it's internal to the unit. I can easily turn it on thR bench. The new one does not turn so easily. I haven't tried to disassemble it to determine why. The old one was working 75% of the time.

[td1238]

Well opening it will probably disclose why.

[colonelhogan44]

IIRC, it's actually a worm gear drive.

I threw my broken one away, and put in a used unit I had on hand. So far so good after 2 years.

When it breaks again, I'll probably just print a new gear on my 3-d printer. Maybe I should design one up and start selling to folks.

[RobertGary1]

Does that work well with harder plastics? My sons used a 3d printer in high school to make little engineering projects but the plastic used seemed to be a bit brittle.

-Robert

Originally Posted by colonelhogan44

IIRC, it's actually a worm gear drive.

I threw my broken one away, and put in a used unit I had on hand. So far so good after 2 years.

When it breaks again, I'll probably just print a new gear on my 3-d printer. Maybe I should design one up and start selling to folks.

[colonelhogan44]

Mine uses ABS plastic, and the parts are very durable.

[RobertGary1]

Well, here is the problem. The final drive gear is slipping on the tube that eventually engages the door.

[alordofchaos]

Originally Posted by colonelhogan44

Mine uses ABS plastic, and the parts are very durable.

It seems there should be some really good uses for something like that... just can't think of any off the top of my head

[colonelhogan44]

I've used it for some prototyping in the past. I've also made a lot of worthless stuff on it -- such as a 3-d model of Captain Ahab's face.



Robert:

Making that shaft/gear one piece could solve all the issues.
Do you have the ability to draft that gear into Solidworks or Autodesk Inventor or similar solid modeling software?

If you (or anyone else) can/wants to draft it and email me an .stl file, I'll print one. All mine are working at this point, and I don't have time to mess with pulling one out just for kicks.

I'd love to try to make one though.

[RobertGary1]

Originally Posted by colonelhogan44

Robert:

Making that shaft/gear one piece could solve all the issues.
Do you have the ability to draft that gear into Solidworks or Autodesk Inventor or similar solid modeling software?

I don't know if I still have access to that imaging. They really don't seem to like it when the engineers go down into the shop, even though there is a sign describing how to sign up to use it after hours. I think they're afraid we'll break their stuff or leave soda cans lying around. However, I've replaced the unit with a new OEM unit. If you're really interested I'd be willing to stick that final gear and collar in an envelop and send it to you.

-Robert

[RobertGary1]

When I installed the new GM actuator I noticed that the drive collar was plastic vs the metal collar on the old unit. It just struck me that its likely that the collar and the final drive gear are likely molded as a single unit now. That would be an improvement on the design (one of the rare cases were plastic is an improvement over metal ).

-Robert

[colonelhogan44]

The one I replaced came out of a 1998, and it was already a single solid moulded plastic gear, IIRC.

If you don't mind sending that unit out, I'll see it it's within the capabilities of my printer to manufacture replacements.

What'd the new unit run you?