Fixing the HVAC flap actuator without removing the clam - LotusTalk - The Lotus Cars Community
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post #1 of 2 (permalink) Old 08-31-2019, 10:21 PM Thread Starter
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Join Date: Sep 2004
Location: Bay Area, CA
Posts: 52
Fixing the HVAC flap actuator without removing the clam

I knew the flap in the HVAC box was stuck because the AC would be cold only in the first 10 minutes of the drive, and the air out of the vent was always hotter than ambient air.

1. Remove the passenger side tear drop panel, fuse box, and near by plastic trims for easier access.
2. Remove the corrugated flexible hose. You'll see the flap of the HVAC box.
3. Turn the temperature knob and see if the flap moves.
4. If the flap doesn't move, check the 12v power to the actuator. The yellow wire to the actuator is the control line, it should be 0-5V depending on the temperature setting.

If the electrical checks out, remove the actuator.

I read that sometimes the flap is stuck because the gear and belt in the front is jammed by little stones, and it can be freed by moving the flap past the resistance point. That's not my case, and I think moving the flap might have made the situation worse. My suggestion is don't move the flap forcefully, unless “helping it in the right direction” doesn’t work. There is a worm gear inside the actuator, so something has got to give if you turn the flap, but the actuator does not turn w/ it.

Now to remove the actuator.
The actuator is fixed to the box by 2 screws. The nuts inside the box can be accessed pretty easily with a right angle driver. The challenge is the screw heads would turn as you turn the nuts.
For that, keep tension to the screw by shoving a flat head screw driver between the actuator and the box.
Undo the last few turns by hand to keep the nut from falling down the box. I put a piece of duct tape to catch the falling ring.
The nuts are on different sides of the flap, so you'll have to loosen one nut, move the flap to the other side to remove the other one. Try not to push the flap without moving the actuator.

Be aware that there is a piece of white nylon connector between the actuator and the flap shaft. It may fall down as you take off the actuator.

After the actuator is removed, you can move the flap all you want.

My HVAC box just needed lubrication.

The actuator didn’t have enough torque to move the flap, but works ok after a few doses of wd40 and multi purpose grease at the moving points.

I got a new actuator for good measure. The Norman 604-5103CD actuator is a direct replacement part, but it doesn’t come w/ the damaged connector that goes from the actuator to the half-circle shaft. If the Lotus actuator comes w/ the connector, I think it’s worth it to get the Lotus one.

Anyhow, I wanted a solid connector, so I fabricated one from solid aluminum and a steel screw.

Some notes on the connector:
The oval connector has a hole. Half of it is round (faces the flap), the other half is half circle. This connector cannot be reversed or else the actuator pushes the flap to the front of the car, and it binds the flap.

There actuator goes beyond the limit of the flap a bit, so I think the oval connector gets deformed overtime, and it will get deformed easily if you move the flap manually.

Making the connector took the most time. I can take off the actuator in 5 minutes with some practice.

To make the installation and removal easier, I epoxied the screws to the new actuator.

Hope this helps.
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post #2 of 2 (permalink) Old 09-01-2019, 08:31 AM
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Join Date: May 2005
Location: Chester, NJ
Posts: 11,224
Good stuff. Thank you very much.

05 elise (BOE Rev300 supercharged, SSRs, shift tower mods, Multivex; HID hi/low beams); 05 Corolla XRS. Past '72 Elan Sprint (I restored), Lotus 7 w/X-flow, TT Supra, Bugeye Sprite, BMW 2002 & 2002tii, '65 GTO.

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