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Acc stepper motor replacement

13K views 10 replies 4 participants last post by  arclite 
#1 ·
Hi

Saab 9000 CSE 2.3T 98: Heat only from ACC. The fault -diagnosed with much help from previous posts on here- appears to be with the stepper motor which controls the air mixing flap this ticks and buzzes when varying the Air temp but does not move the control rod. Does anyone know if this is a reasonably easy replace through dash top? I would be grateful for any info. There appears no info of how to do this job either on the net or in Haynes

Rgds

Alan
 
#2 ·
IIRC it was a bit of a fiddly job to take out (I took it out of a CDE I stripped) I think - and may be proven wrong here - that it is rivetted in place so you my need to drill the rivets out.
If you remove the dash top and the instrument binnacle you should have enough access - the really difficult issue is parting with the £230 or so that a new one costs.

Arclite got mine, so a PM might yield more information on changing it.
 
#3 ·
Thanks for this - I took the Dash top off and had some access but I would guess at least the binnacle also needs to come out - I checked the part out on saabsite and the replacement appears to be part n0 5172580 at least that looks like the part not working on mine - Id it is the dealer price is around £65- of course I may have id'd the wrong part

Rgds

Alan
 
#4 ·
as you may have noticed i have had trouble with my motor i found the easiest way for me was to go through the front of the dash by removing the clock and the acc unit as i did not no how the top came of and if it was going to be a nightmare getting it back on. the stepper motor is screwed to the metal plate and the little alu arm should just slide of with a little help. have you tried two stroke turbo as they are around £90have fun fittting it all in and can you let me no if it is easier to refitt with the top of dash off and how hard it is to get it back
 
#5 ·
Hi

The dash top is pretty easy to get off - follow previous posts on here - take care with the small screw under the instrument binnacle just above the tacho - it is very easy to lose behind the panel - also when refitting fit this screw first - I don't know how you manage to access the stepper motor for changing with just the acc panel & clock out - congratulations!

Rgds

Alan
 
#6 ·
[ QUOTE ]
I don't know how you manage to access the stepper motor for changing with just the acc panel & clock out - congratulations!


[/ QUOTE ]

Quite.
I would have paid good money to see that. Could you pop round and decorate my hallway - you should be able to do it through the letter-box

Very thin arms with two elbows on each, I shouldn't wonder.
 
#7 ·
<font color="blue">How many people reading this article would prefer to replace just the essential failed component for a lower cost? PM's please with the motor ident + "w/gearbox" if required in the subject line. I'll tally the results and publish.</font>

It may be that you have been very unlucky with this motor. They are built in such a way that they do not overheat if they are 'jammed' by external frozen components. The motor bearings are sintered bronze and are self lubricating, not something to wear out easily.

If you have seen an earlier post with a 'free' actuator arm, a simple solution suggested was to epoxy the arm to the gear spindle.

There are 2 motors, each with a different ident codes which relate to the motor function. Also there are two gearboxes from the same company and if a fault has occurred here, replacing the motor will not help much.
 
#8 ·
Thanks for the comments Arclite - I'm insufficently up on this subject to understand the references to the 'gearbox' or second motor - accessing through the Dash top the stepper motor - part no quoted previously - does not move the thin rod connecting thro the firewall to the mixer flap when varying the heat. - when the arm on the motor linking to this rod is pushed or pulled while varying the heat it will move - you can feel it skipping against- presumably -toothed cogs - this I understand may be the gearbox referred to, altho I assumed the mechanism would be part of the motor. It looks as tho the stepper motor - when comparing to the illustration on the saabsite - is a single entity that moves the arm,altho I may be quite wrong in this Saab Main dealer have quoted 65 for the motor and around 100 to fit - I may get them to look and confirm the repair required anyway. You are quite correct about the reliability - the Main dealers have fitted only 3 in the last 2 years - and they were used on the 95 98-03 too.
 
#9 ·
Apologies... I'm looking at the infamous flap actuator assembly sold to me by Trollbooster a while back. The complete assembly is a pressed steel plate essentially in the form of 3 steps with a total of 3 fixing points.

2 of the steps form a base for the 2 stepper motor sub-assemblies and the 3rd step holds a 10 point multi-connector from which is also the ACC mixed air temp sensor.

The motor sub-assemblies are themselves comprised of a stepper motor with 2 fixing screws and these are screwed to the top of a 'pear' shaped gear housing or 'box'. This is a steel face plate and a black plastic surround.

The motor ident is printed on a white label covering the free end of the motor beginning with "UBB". The gear ident is stamped into the gear housing face plate.

Have you re-calibrated the ACC system? (see recent posts for descriptions)

A stepper motor drives the flap arm through a gearing, but the gear output is restricted by 2 end stops (hidden under a black plastic cover). I am assuming that 1 function of recalibration is to allow the motor controller to 'sense' the stop points and to provide the corresponding motor step counts between 'stops' to give full flap control to the ACC controller. Without calibration the 'stepper' motor step pulses and pulse counts will not represent the current flap position.
 
#10 ·
Hi Arclite -I recognise your description of the complete assembly now altho I did not note the second motor. After checking the rod betweeen the stepper motor and the mixer flap arm was connected ok (re: quasimotor) , I tried recalibrating several times using instructions found on here -unfortunately this did not solve the problem - during recalibration the stepper motor tries to move the rod but again you can hear the cogs skipping. I'm pretty sure therefore the problem is within a gear mechanism -If this is not an integral part of the stepper motor, then I take your point about replacing the motor only, I'll check with the main dealer and have a look at the actual component

Rgds

Alan
 
#11 ·
[ QUOTE ]
stepper motor tries to move the rod but again you can hear the cogs skipping

[/ QUOTE ]

Sorry to be such a pain... I am interested in your description here. Previous post has described the fitting of the motor spindle to the actuator arm as "splined" i.e. with grooves to lock with similar on the arm. Slippage between these 2 components would be as rapid 'ticking' the same as gear slippage unless you knew the frequency of ticks would always be different in each case.... e.g. 4 ticks per second for the actuator arm, anything between 10 and 20 ticks per second for any point of failure in the gear assembly.

Does anyone have any experience that can be shared on this point ?? To be honest I have not seen inside the gear assembly or seen the splined parts of the assembly so I am unable to add any further comments.

However if when you come to replace any key parts, investigating the root cause of the sound itself may assist future SAAB owner/drivers in making an immediate diagnosis of the required replacements or actions and costs.

Good luck!

P.s. with mine being a vertical letter box, could you paint the hallway ceiling as well as the walls when you've finished doing Trollbooster's?
 
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