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Hello all,

There is a clicking noise under the passenger side dash of my 99 Esprit V8. My tech says it is the arm on the Steppermotor that is stripped so it just keeps turning over and over (number 13 in the diagram?). Lotus does not stock them anymore. And, one garage here in Los Angeles says it takes 25 hours to remove the dash to replace it. That seems a bit overboard.

1. Does anyone have a Steppermotor they can sell to me?

2. If not, is there a good fix for It without removing the entire dash?

Cheers!

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Upgrade today to remove Google ads and support TLF.

I think you can just about get access to the stepper motor from right hand side footwell. It might make things easier removing right hand seat and lie in backwards on your back.

As for a simple fix, it's usually a burnt out resistor, I do t know the values but I know it's not a common one. My friend here in UK fixes these along with ECU's if you get stuck.

Regards

David

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Hi, I have had the same problem. My car is a 2002 V8. The plastic arm is striped on the drive of the stepper motor. To remove the step motor you need to dismantle the dash a bit. there are three bolts that hold the motor in place. You may be able to get at it through the radio hole and remove some of the controls below that. Remove the seat for sure and you can get at two of the bolts but not the third one. I had a machinist friend make a new arm with aluminum and used set screws to attach to the motor. So far been in place for two years and stays on. The motors don't seem to be the problem. The arm is, and when actuated rotates and opens the flap then stops. I tried epoxy to repair the plastic arm and no luck! Its a operation of patients to remove the stepper motor.

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I've done it through the radio hole, there was no need to remove the seat. Remember using a VERY long screwdriver though, not the sort you would find in the average toolbox.

 

The stepper motor was a Diavia part if it's any help

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Hi Howard.  Wish I could report complete success with my attempted fix.  Any way, here is my attempt at a fix.  I agree with Jamie the first thing to address is the fit of the motor arm to the motor shaft.  Not sure if the motor controller is integral to the stepper motor; perhaps some others can clarify as that may have to be my next item to fix.

 

The motor arm is easily removable from the stepper motor from below the dash.  Pry the plastic motor arm hub off of the knurled motor shaft with a small screw driver.  You may find the arm just hanging from the control rod (part 15) by the nylon clip (part 16).  Mine routinely falls off the motor shaft due to the motor cycling at the top of travel.  The arm hub may look OK when viewed under the dash, but once off the shaft it will probably be split at the hub hole.  The nylon clip (part 16) is easy to pry off the control rod so you can take the motor arm to the bench.

 

Based on Jamie's and others success of fixing the cycling issue I have attempted to fix the motor arm fit using a drilled out shaft collar.  I can't recall the size I used; I just bought a few and drilled out the one that would fit without interference.  The grub screw can still be tightened on to the arm hub, or hopefully with a longer grub screw directly on to the motor shaft.  Here is a link to a site showing the various sizes of shaft collars to give you an idea.  Search on 'shaft collar':

 

www.princessauto.com/en/home

 

So, a few weeks ago I tried fitting the collar.  Unfortunately the motor kept cycling.  I think I need to get a longer grub screw to get a tight fit to the shaft.  My car is presently in winter storage, so won't be able to follow up for a while.

 

I am not sure how the stepper motor controller knows it is the end of travel.  Hoping that the motor simply stalls, similar to the headlight pods?  Based on the behavior of my motor it appears to be a simple two position stepper (either fully up or fully down).  Maybe someone can confirm this is how it works?

 

HTH.  Let us know if you get the issue resolved.  I understand it is a pretty common issue, and the system is not well described in the service manual.  Also understand the motor and controller are NLA.

 

Stu

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A quick couple of adders to the post above. 

 

I checked my notes, and the shaft collar size I used was 5/16".  The included grub screw is 10-32.  I got longer Paulin grub screws at Home Depot in 10-32 x 1/4".  I can't recall the drill out size I used, but I just matched to the OD of the arm hub at the bench to create a friction fit of the collar over the hub.  IIRC the 3/8" shaft collar was a bit large to fit the length of the lever hub.

 

From playing with the heater controls, this stepper and flap directs the heated air between the windscreen defroster vents and the footwell hose.  With the rod / lever in the raised position the air is directed to the footwell; lowered position it is directed to the windscreen.  I believe there is always a minimal amount of heated air to the windscreen.  I think it is knob number 6 Distribution Control that controls this stepper motor.  I think mine works with the key in the 'ON' position, but other guys said they have to have the engine running.  Note there is a separate control run on vacuum that does require the engine running to work.

 

Here is a picture of the shaft collar I am using.

 

Stu

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You definitely don't need to remove the dash.  Access to the motor is via the aperture for the radio.  It's fiddly to get at and remove but not impossible.  Then, follow the above advice for repair.  Good luck

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Bringing this thread forward to report results.

The shaft collar idea did not end up working too well for me.  I just could not get my damaged control arm tight enough on the stepper motor shaft.

I came up with another idea, and so far it is working well.  I used a servo control arm that are typically used in model aircraft.  The part I used is from Hanger 9, P/N HAN9161, 2" aluminium single arm (HTC).  The hobby shop had several servo arms in stock, but I figured the aluminium one had the best chance of fitting tightly to the stepper motor shaft.

http://www.hangar-9.com/Products/Default.aspx?ProdID=HAN9161

The replacement arm is slightly longer than the stock arm, but it fits without fouling anything so it does not need to be cut to length (at least on my LHD car).  The arm comes with a selection of socket head screws to tightly attach the arm to the stepper motor shaft.  The aluminium can be easily drilled out to the stepper motor shaft size. Recommend using a slightly smaller bit size to ensure the arm fits tightly to the shaft. The arm is slotted around the shaft hole to allow the socket head screws to tightly clamp to the stepper motor shaft.

I also drilled out the first servo arm hole to accept the stock plastic rod clip.  Then a simple matter of clipping to the flap actuator rod.  The effective length of replacement arm ends up slightly longer than stock, but still works fine.  Just means the arm motion will stop slightly short of the stops on the motor mount.  It is possible that this makes the flap fit more tightly than intended, but works OK for me.

Due to limited access under the dash I was only able to get one of the socket head screws tightened to clamp to the stepper motor shaft.  The one that screws in from the top is too hard to get to with an Allen key. Tightening the one that screws in from the bottom still retains the arm tight enough to stop the motor motion at the two flap end positions.

To orient the arm on the servo motor shaft, recall that the arm in the down position corresponds to the air flow from the defrost vents, and the arm in the up position corresponds to the air flow to the floor vent tubes.  On my car the motor only stops at the two extreme arm positions; there is no intermediate arm position.  Not sure if this is correct, but that is how mine works.  A secondary vacuum controlled flap closes in the air conditioning position, but this is separate from the stepper motor action.

Here are a few pictures that show the replacement servo arm with the stock piece.

HTH

Stu

image2.jpeg

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image8.jpeg

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Stu

looks like a good fix. Two questions:

So you don't remove the stepper motor to fix this on?

and do you have to "set" the motor in position somehow before attaching the arm? or just fix the arm on in any position, and the sensors sort it out?

thanks

Stu

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Ha, mine's just gone into full 'manual' mode.  My flap is now actuated by reaching down to the right of the console and manipulating the rod that's hanging loose there.  Guess I have a similar job to do... 

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1 hour ago, LotuStuart said:

Stu

looks like a good fix. Two questions:

So you don't remove the stepper motor to fix this on?

and do you have to "set" the motor in position somehow before attaching the arm? or just fix the arm on in any position, and the sensors sort it out?

thanks

Stu

The stepper motor does not need to be removed.  The stock arm can be gently prised off of the stepper motor shaft; it is just a friction fit with no retaining screws.  If you are having an issue with the arm slipping it is probably cracked in the attachment hub.  The new arm fits over the shaft after drilling out it's attachment hub.  Start with a small bit size; I drilled it a bit large and had to grind the mounting slot wider to get the attachment firm enough.

The way I indexed the arm is to cycle the motor by manipulating the dash knob a couple of times, and then setting it to full defrost.  With the motor stopped in the full defrost position (I think it takes about half a minute to stop), the new arm needs to be in the full down position.  The easiest way to do this is to attach the arm to the control rod first with the plastic clip, and then slip it on the stepper motor shaft.  Snug up the arm Allen screw a bit.  Now pull the arm all the way down until the flap or the motor stop prevents it going lower.  Lighten the Allen screw fully and the arm is indexed.  Cycle the motor a couple of times to observe it is working correctly and allow the thing to fully index.  

I tried to rake a couple of pictures of the motor and arm, but they were not clear enough.  Basically crawling under there in the Lotus position with lots of light and it becomes obvious enough on where the motor and arm can be pried apart.  My car is LHD, so not sure how it works for RHD.

As with the light pod motors, it appears to simply be a two position stepper that works by stalling at the two extreme positions.  Basically the arm is in the down position on defrost and in the up position in every other setting.  The A/C setting moves a different rod by vacuum. but the stepper motor position does not change  I sort of expected an intermediate position relating to the knob position with the two arrows, but mine just chugs on to the air to the foot well position (arm all the way up).  Maybe someone that has a fully working heater can check if this is how it works?  In any case, the controller and motor will not work properly without the arm attached very firmly to the stepper motor shaft; with the stock arm hub cracked the motor cycles as it never fully stalls against the stops.

HTH  Is yours cycling at the two extreme positions?

Stu

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1 hour ago, Sparky said:

Ha, mine's just gone into full 'manual' mode.  My flap is now actuated by reaching down to the right of the console and manipulating the rod that's hanging loose there.  Guess I have a similar job to do... 

My arm would eventually fall off from the cycling.  Remove the arm from the plastic rod clip by pushing the clip off the rod and then removing the rod from the centre of the clip.  The arm can then be taken to the bench for examination.  I expect you will find the plastic hub is cracked; in my case the crack was on the top side so you could not see the damage without removing the arm completely from the car.  Hopefully the model airplane replacement will fix the system.  

With the key in the run position, check if the stepper motor is still moving when you cycle the dash control knob.  If the motor still moves. a new arm may fix it up.  

Stu

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Cheers Stuart.  I shall have a rummage tomorrow.  :-)

 

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Hey Sparky looks like we may have another get together-this is my fun type of thing to do.....if i can get the car out of the garage...

maybe worth buying 10 of these aircraft arms for others in need in hte future. weirdly, mine stopped cycling for a bit, but i think it went wrong again

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LotuStuart and Sparky, I did a bunch more research on the V8 heater.  I posted the gathered info and reference pictures here....

http://www.lotustalk.com/forums/f164/c-air-distribution-flaps-338569/

One part I am still a bit confused on is the exact differences between LHD and RHD stepper motor mounts.  Before trying the stepper arm fix, please check out the photo's on the thread and take a look for access.  

My thought is you may have difficulty tightening the replacement servo arm on to the motor shaft without taking the motor out. On my LHD car I am pretty sure the motor shaft is towards the front of the car, so I could reach the socket head screw on the arm fairly easily.  My car is in for repairs so i can't double check it right now.  Are the RHD motors mounted so you can remove the arm easily and re-install the replacement?

HTH

Stu

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Cheers Stu - excellent reference.  My stepper is on the same side and the arm is easily manipulated even whilst driving, so hopefully *just* a matter of reconnecting.  I haven't viewed the motor's operation yet, but I can hear something moving when I twist the knob - so hopefully it's OK.

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