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Blend door stop tabs broken
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rsippel
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Dec 8, 2012, 6:30 PM
Post #1 of 31
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Blend door stop tabs broken
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I have a 2005 Buick Terraza. The right side blows cold only--dual temp controls (manual). I pulled the glove box and looked at the blend door actuator. The actuator moves on command from the temp dial, but it moves too far out of range and disengages the two gears. There are two platic tabs that broken off the heater box that were there to limit the range of the actuator gear.
I was thinking of just epoxying the tabs back on. But I am not sure the actuator will not break them off again. What stops the actuator when it hits the tabs? Could the actuator be bad and stopping when it should? Or is the top point controlled by the temp dial or HVAC head unit? I can get the actuator to work in my hand, but not sure how to test if will stop when it is suppose to.
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Hammer Time
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Dec 8, 2012, 6:49 PM
Post #2 of 31
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Re: Blend door stop tabs broken
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Don't think epoxy is going to do the trick there. If you Google "Blend door repairs" you will see some stuff that people have done but the only real good repair is a new door and that means ripping the dash out.
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rsippel
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Dec 8, 2012, 7:05 PM
Post #3 of 31
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Re: Blend door stop tabs broken
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I understand the epoxy may or may not hold the tabs in place. But before I try it, I wanted to know if the actuator was responisble for stopping the motor at the point where it hits the stops. Could the actuator be bad and not stopping? and is there a test for this? Or is it controlled by the temp dial at the head.
i don't want to try fixing the tabs unless I am sure there isn't another problem that doesn't allow the sactuator to stop when it hits the tabs.
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Hammer Time
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Dec 8, 2012, 7:08 PM
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Re: Blend door stop tabs broken
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It goes through a self calibration against the stops so it has to be strong enough
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rsippel
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Dec 8, 2012, 7:12 PM
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Re: Blend door stop tabs broken
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I want to try it, it is not just replacing the door. The stop tabs are on the outside of the whole box that include the doors inside. The stop tabs are to stop the actuator gear on the outside the box...so it would be replacing the entire box not just the door.
Just wasn't sure how to test that it will actually recalibrate and stop. Wasn't sure if they broke becasue they were weak or whether the actuator or temp control was bad and not telling the actuator motor to stop???
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Discretesignals
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Dec 8, 2012, 7:12 PM
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Re: Blend door stop tabs broken
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The actuator's circuitry detects the servo motor stall as the door hits its stop. The stalling of the motor causes a surge in current the circuitry in the actuator detects, so the circuitry kills the servo when the motor stalls. There is also a potentiometer inside the actuator that a climate control processor uses as an input to determine the position of the door. The computer has to learn the position of the door by stalling it at both its open and closed positions, so it is able to properly position the door depending on the desired temperature selection. The stall puts stress on the door linkage. The design of the door or the strength of the plastic is the factor if the door can handle the stress during calibration or during the motor's stall. The gears inside the actuator can also break when overstressed because they are plastic, which is a common problem too.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Dec 8, 2012, 7:14 PM)
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rsippel
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Dec 8, 2012, 7:25 PM
Post #7 of 31
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Re: Blend door stop tabs broken
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Thanks for the reply. The doors are still working fine and the actuator moves on command. The stop tabs that are broken are on the outside of the housing box. There are two larger gears on the outside. One that is connected to the doors. The 2nd gear drives the door gear and it is this gear that the actuator gear inserts into. It is also this gear that hits the stop tabs on the outside of the box to limit its range. My only conern is fixing the stops, but not solving the problem. Is there a way to tell if the actuator is recalculating at the stop point and not trying to push further and breaking the tabs again?
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Discretesignals
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Dec 8, 2012, 7:27 PM
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Re: Blend door stop tabs broken
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Well, you could plug the motor in and then attempt to stall it manually. If the actuator peels the skin off your fingers, then you know there is something up with it...LOL
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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rsippel
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Dec 8, 2012, 7:31 PM
Post #9 of 31
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Re: Blend door stop tabs broken
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Well that got me laughing as well. I tryied the hand/finger stop earlier, but learned quick that these things are strong. I was able to stop it "sometimes" and sometimes I let go before the skin tore off ! Thought there had to be a better method to stop it and if it didn't stop was it the actuator to the temp control?? That was issue I was trying to sort out.
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Discretesignals
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Dec 8, 2012, 7:39 PM
Post #10 of 31
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Re: Blend door stop tabs broken
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It's hard to say what kind of force you have to apply to the shaft before the servo is turned off. There aren't specifications of this in service data. You almost need some sort of device to attach to the end of the motor that applies resistance to the shaft and measures the amount of torque. Almost like a dyno for measuring torque of an engine, but one for a door actuator. The cut off point is the maximum amount of torque the servo achieves before it is turned off.
You would still need the specifications to compare your results too. You could get another servo and do your finger comparision to see if there is a difference.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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rsippel
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Dec 8, 2012, 7:49 PM
Post #11 of 31
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Re: Blend door stop tabs broken
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Well given the actuator moves on command I guess I will assume it is not faulty and just try my epoxy method. If it stops, good. If it breaks then I will try something else. I just wanted to rule out a faulty actuator or other faulty control that may have been causing the actuator to travel too far even after hitting the tabs and breaking the tabs.
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Discretesignals
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Dec 8, 2012, 7:54 PM
Post #12 of 31
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Re: Blend door stop tabs broken
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There are several factory service bulletins (TSB) on problems with HVAC door performance, but none are addressing the tabs breaking off. All of the TSBs state to reprogram the HVAC control module with an updated calibration. Might not be a bad idea to have the dealer or someone with the ability to program the HVAC module with the latest and greatest software after your repair.
Probably wouldn't be a bad idea to test another actuator to see if it takes a lot of force to stop it.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Dec 8, 2012, 8:03 PM)
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Sidom
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Dec 8, 2012, 7:55 PM
Post #13 of 31
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Re: Blend door stop tabs broken
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A lot of times those outside gears will come with the new actuator if you get one from the dealer..... Go down to the dealer and look at one they have in stock & see if it is what you need...
If the tabs you are talking about is part of the box, gluing won't work but if you can get a sheet metal screw to go in place where the tab was, that may work as a stop.....
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rsippel
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Dec 8, 2012, 8:06 PM
Post #14 of 31
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Re: Blend door stop tabs broken
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Well that was my idea as well. The tabs can be placed back in on their sides giving about a 1/2 x 3/4 inch flat surface to epoxy. Was thinking I would scratch both surfaces and then epoxy (maybe with a jb weld for plastic) . then put a small-short screw through the tab and into the box surface. Just didn't want to go too far in so as not to screw into something else inside and create a bigger problem.
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rsippel
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Dec 9, 2012, 11:34 AM
Post #15 of 31
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Re: Blend door stop tabs broken
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Well i guess I will just try it. Only real concern I have is whether the actuator will stop at the new tabs or if something else is wrong and not calibrating the stop positions.
Thanks for all your comments and advice.
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Sidom
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Dec 9, 2012, 12:17 PM
Post #16 of 31
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Re: Blend door stop tabs broken
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It's too bad you could post a picture or something... I'm having a hard time picturing these "stops" you are talking about..
Usually on these type of problems it's a bad actuator. You see this happen when the battery gets disconnected without a memory saver & then hooked back up again.....The actuator breaks on relearn...
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rsippel
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Dec 9, 2012, 12:49 PM
Post #17 of 31
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Re: Blend door stop tabs broken
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Okay trying to attach picture, but I don't see how to attach a pic to the reply.
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Hammer Time
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Dec 9, 2012, 1:25 PM
Post #18 of 31
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Re: Blend door stop tabs broken
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You have to upload it to an image hosting site like Photobucket or Imageshack and they supply a link to post in your answer that makes the pic show up here.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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rsippel
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Dec 9, 2012, 1:40 PM
Post #19 of 31
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Re: Blend door stop tabs broken
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Okay took the imageshack advice. If all works, there should be an image of the book diagram with a comment. IF this isn't clear I will take a pic of the actual vehicle. Try this link.
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Hammer Time
Ultimate Carjunky
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Dec 9, 2012, 1:46 PM
Post #20 of 31
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Re: Blend door stop tabs broken
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I'm still a little confused as to what you are referring to as "stops". As a rule, these things have no stops. The door itself reaching the end of it's travel is the stop.
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rsippel
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Dec 9, 2012, 1:51 PM
Post #21 of 31
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Re: Blend door stop tabs broken
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Here is another pic of the actual vehicle. Again, the actuator sit over the gears with actuator shaft inserted into the center of the left gear. The light colored L shaped markings left of the left gear is where the tabs were that have broken off. As you can see they set the L/R limit of the gear. Image
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Hammer Time
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Dec 9, 2012, 2:05 PM
Post #22 of 31
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Re: Blend door stop tabs broken
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I doubt crazy glue alone is going to hold them. I would try first getting them set in place with crazy glue and then use some JB weld or equivalent to reinforce them but make sure you don't put the epoxy where it will interfere. Do not connect the battery until it is completely dry.Otherwise it's going to mean replacing the whole housing to resolve that.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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rsippel
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Dec 9, 2012, 2:15 PM
Post #23 of 31
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Re: Blend door stop tabs broken
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Never intended to use glue. As you can see in the photo, I have begun to scratch up the surface. I have made two plactic tabs that I will epoxy in place with JB-weld. I was also planning on putting a screw through the new tabs into the box. I drilled a very small hole in the box to check for the screws interference with other doors. Looks like I will have enough clearance for a short screw through the tabs and into the box.
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Hammer Time
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Dec 9, 2012, 2:18 PM
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Re: Blend door stop tabs broken
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Don't penetrate anything through the case as it will likely interfere with the door sweep.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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rsippel
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Dec 9, 2012, 2:24 PM
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Re: Blend door stop tabs broken
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Thanks for the reminder about the battery. I have the actuator disconnected now, and I will disconect the battery before I hook it back up. As for the box, I drilled a very small hole and inserted a small very small rod in the holes at the depth the screw would go in. I then cycled through all the HVAC functions of defrost through lower vents and manipulated the blend doors. Nothing seemed to interfere. I did find if I went further in, it would hit a door. But at the planned depth all was fine.
(This post was edited by rsippel on Dec 9, 2012, 2:25 PM)
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