Hi, looking for some help diagnosing / repairing this aircon actuator. I’ve read some of the excellent posts on this part such as: https://www.ferrarichat.com/forum/threads/new-owner-with-ventilation-problem.514304/page-10 But i has a couple of quick questions that I hope someone can help me with. the unit appeared to be seized and I feared the gears had broken as the main gear taking drive from the motor gear seems weak. I opened the unit and amazingly this gear seems in good condition. I tested the motor and that seemed good. The problem seems to be that the gears seem to run fine, but I only get friction free movement around 180 deg. So looking at the unit with the motor at the bottom, I can power the actuator from the 12 o clock position anti clockwise until the 6 o clock position. Anything outside of this range is really stiff. my question is, what is the range of movement this actuator needs to operate across? Should I be getting movement thru 360 deg? Image Unavailable, Please Login Image Unavailable, Please Login
I don't know how you're getting more movement than 180 degrees. That's the full range. What are you using to drive the actuator past 180?
What do you mean by seized? Was the unit not running when you applied power to the red and black wires (reversing the polarity to get the actuator to run in a different direction)? Are there plastic stops at 12 and 6 (say, on the potentiometer)... and have you broken them?
I was just applying 12v to red and black wires to test the unit. I think you’ve answered part of my question; as I was thinking that the actuator range of rotation would not be the full 360deg and it seemed to struggle going past 0 deg clockwise and 180 deg anti clockwise. Am I right in thinking that the AC control unit uses the potentiometer readings to determine the position and hence limit the movement? Or is there a physical hard stop on the unit and is this somehow not working fully on my unit?
ok, I’ll try and explain the steps I have taken so far…. The AC evaporator flap was not moving and we assumed the actuator was not working. When we removed the actuator and applied 12v to the red and black leads there was some noise from the motor but the spindle didn’t move. I assumed either the motor was at fault or the gear system had seized, possibly due to broken teeth as that’s what a lot of the other posts had reported. after opening the unit it appeared that the usual suspect (main wheel gear) looked fine. So I assumed the motor must be at fault. After removing the motor and applying power the motor seemed to run fine but I noticed that whilst the wheel gear would turn, it was quite stiff. After turning it further it began to free off and when I placed the motor back in the actuator seemed to run smoothly when power was applied. I then tested it some more and noticed it would work well within the ranges 0 - 180deg anti-clockwise, but struggle anywhere outside of this range. not knowing much about the operation / control of the A/C servo-mechanisms, it did occur to me that this might not be a problem if this was the range it was required to operate. So I guess my question is; should the actuator have hard mechanical limit stops at 0 and 180 deg or are the limits implemented as part of the servo controller? your questions seem to imply I should me mechanically limited. If it is, will the lack of hard limit stops cause me problems?
The gears in those actuators break. They are kind of fragile. Last time I needed one it was available as a separate part. That was a long time ago.
When I test a spare actuator off the car, it has physical limits, but the HVAC ECU may learn the limits with ignition on (or battery off/on) from both physical limits and potentiometer readings. Once it has the resistance readings at full clockwise/anticlockwise, it can position the actuator at intermediate stops using potentiometer resistance.
Strange (especially with the gears ok). If you're just applying power to the motor, how can the gear wheel seem "stiff"? Slow to move? Or are you assisting with your fingers?
I don't understand how you're getting past the 180 degrees at all. Mine stops and I'm not going to force it past there. Maybe someone in the past forced it past 180 degrees and broken the physical stops? When reinstalling the actuator on the car, are you aligning the index mark on the actuator with the index mark on the evap unit?
On my spare actuator, the drive is square, not like yours, but it still has a small index mark. I've been told that the spindle of the tambour has a corresponding index mark which must be aligned. I thought I had a photo of the index mark on the tambour, but I can't find it.
Is the actuator still in pieces? Can you determine if the physical stops are part of the potentiometer assembly? Typically, potentiometers have (internal) physical limits.
Thanks to @Mike Morrissey here's a photo of the index mark, currently at the 12 o'clock position ... Image Unavailable, Please Login
So looking at that picture, would I be correct to say the limits of rotation of the tambour should be from 12 o'clock thru to 6 o'clock in a clockwise direction?
I don't think there is a way to tell without disassembling the potentiometer, which requires the spindle and gear assembly to be removed. I'm guessing the pot doesn't have limits, as it looks quite small/flimsy and if there were stops it will be on the spindle itself.
Is this with the potentiometer removed from the unit, John? If this is the case, then the 180 degree limit on motor rotation (unit not fitted and just power applied) must be some other physical limit in the motor. From what I've been told, the tambour rotates infinitely through 360 degrees and beyond. The actuator range is 180 degrees by just putting power on the motor. i.e. with no influence from the HVAC unit. The physical stops must be within the actuator. When you said you can power the actuator anticlockwise from 12 to 6, do you mean in the orientation shown in your photo? Image Unavailable, Please Login
I had to edit my last message. When I checked my spare timer actuator with a battery, it moved through this arc... Image Unavailable, Please Login (using your photo). There was a tiny overrun at the 6 o'clock position (not shown) towards 7 o'clock. This means the actuator drive as viewed from the right side of the evaporator unit will travel between 12 and 6 via 11, 10, 9, 8 and 7 o'clock. (Sorry... another edit). I said left side, then had to correct myself.
Thanks for all the information! It's mind boggling how much information you guys have. So I think to summarise, the unit I have seems to be lacking the end stops. Instead of limiting the range of movement, it gets really stiff and grinds to a halt randomly when it goes past where the end stops should be. After a bit more experimenting, it seems generally that the motor or mechanism works powerfully in anticlockwise motion and more weakly in clockwise rotation. This means it stops more predictably at the clockwise end position (12 o'clock) where the motor seems weaker (or maybe gear friction is higher) and will have a tendency to push past the stops during anti-clockwise rotation. NOTE: these directions are as per this picture (thanks for the edit!): Given this situation, it raises two immediate concerns: a) The weak activation of the motor (or maybe gear friction?) in the clockwise direction concerns me as it may not be powerful enough to adequately rotate the tambour. I think I will just need to test this, but to fix it may need a new motor or more investigation into the spur gear stages by further disassembly of the unit. b) Will the lack of stops cause the problems with the calibration of the controller? I think I read somewhere that the servo controller does a calibration of the position potentiometer by moving the actuator from one end stop to another and reading the values at each extreme to determine the end positions. It seems to me that lack of end stops will cause big problems here and the calibration process will not work and it will not be able to control this actuator movement. However, those above issues may be a mute point, as it appears my actuator doesn't actually work in the required range. I had assumed from my experiments that the stiff area of operation was in the range of where the end stops should have been and the free-running range was in the correct range of movement (as pictured above). However, it appears that the correct range of movement should be from 12'o clock through to 6 o'clock in a CLOCKWISE direction when viewed like this: My unit doesn't move in the range pictured above! If this is the case, then I will definitely need to explore the the spur gear stages to see what's causing the friction in the range of movement. I will report back.... PS. if anybody wonders why I would spend so much time trying to get a small actuator to work, I was going to just buy a new one as Eurospares listed it as a £50 item. However, on ordering the price went up 10x to around £500 with taxes! Which is insane and I thought it would be worth diving into a little before just buying a new unit. I didn't think it would be quite the Rabbit-Hole it is, but I've learnt some things along the way ;-)
Just noticed that the tambour key hole does not have a cut out, so as long as I move the actuator shaft into the right position I’m thinking I should be able to get the required range of movement?
There is a mechanical stop in the mechanism. One in the casing and there are stops on the main gear which limit the rotation to 180*. Image Unavailable, Please Login Image Unavailable, Please Login
I'm not sure how you would align things without an index mark on the tambour key hole. The tambour could end up 90, 180 or 270 degrees out. You may have to experiment with some kind of manual square drive (actuator not fitted) and physically check the airflow is going into the right direction. But even then, what is 12 o'clock? Is it windscreen demist? I'm pretty sure it will cause problems. On the contrary, we do know why you are spending so much time on this. I'm surprised you could even find an actuator at UKP500. People are 3D printing their own gears because they haven't been able to find one. By the way, there is at least one repair company (It's in the USA... Where are you located?): https://www.ecudoctors.com/products/ferrari-355-climate-control-a-c-63307100-br-timing-actuator-repair# Thanks, John!
Thanks for that photo. I think the tabs must have broken off. looks like I’ll have to disassemble the spur gear unit and work out how to mend the tabs. Any advice on taking the mechanism apart? Particularly, the best way to detach the melted plastic posts without destroying everything!
Think about these broken gears it occurred to me that they transmit very little torque. Makes me wonder if it would be possible to replace the larger gear, which breaks, with a rubber roller which rode tight against the small motor gear. There might be some slippage during calibration but assuming the ECU is looking for constant voltage from the pot when the stops are hit, to indicate max/min positions, that wouldn't necessarily be a problem. Even trying to hold the output shaft manually, very little torque is applied by the motor to the larger gear.
