Stepper Motors and Gears FAQ (Frequently Asked Questions)

 

My Alfa 164 automatic cabin climate control system is malfunctioning. I press the buttons on the control panel but I can't get the air to go where I want (feet, face, defrost etc), AND/OR it keeps blowing the same temperature air (hot/cold) regardless of the setting on the LCD. What could be the problem?

-In many if not most instances these problems are caused by a failure of a part of the climate control system generally called the "stepper motors". For more, read on.

 

What is a stepper motor?

-A small electric motor which carries out instructions from the climate control computer (ECU) to drive a tiny gearbox which provides the mechanical actions required to control the flow of air in the cabin.

View a stepper motor and gearbox assembly

 

Do the stepper motors break down or fail?

-Usually it's the small gearbox attached to each of the two stepper motors that fails first. In fact, the failure of these gearboxes is a very common fault of the 164 throughout (as far as we know) all its years of manufacture.

 

How can I tell if a stepper gearbox has failed?

-As mentioned, the temperature of cabin air will not be able to be varied (that's controlled by one stepper gearbox) or the direction of the air to feet/face/etc (that's another stepper gearbox). Or neither, if both stepper gearboxes are faulty.

AND, most commonly, you will hear a clicking (or even a light grinding) noise at regular intervals, coming from inside the dash (facia) as you try to change the cabin temperature or the direction of air flow.

However, if a mechanic or previous owner has tired of this irritating noise without fixing the problem and has disconnected the steppers there will be no action and no noise either.

 

Is it a big job to check the stepper motors and repair the gearboxes?

-It is time consuming, so most quotes from Alfa dealers and others to get access to the steppers and effect a repair reflect the cost of someone doing that work. However, with thorough preparation the whole repair can take less than a day and be done by a competent and patient DIY'er.

 

What would my Alfa dealer or mechanic usually do to repair this problem?

-If the steppers or gearboxes or other in-dash components are suspect the dash (facia) has to be partially stripped, unfastened and pulled away to give sufficient access. Once in there the dealer will replace the stepper motor and gearbox assembly (the motor and gearbox are sold together and are available only from Alfa as one combined unit).

 

So that's a good repair?

-Not in our view. The replacement assemblies, to our knowledge, are little or no better than the ones they have just removed from your car because the gearboxes still contain small plastic gears liable to fail again within too short a time. Furthermore, the stepper motors were probably fine all along, and it was only the plastic components in the gearbox which needed to be replaced. And there's more... the motor/gearbox assemblies are made by Bosch but sold exlusively by Alfa at what seems to us to be a very high price considering the product is essentially the same as the flawed design you have removed.

 

OK, what is AlfaPro.com's solution then?

-We suggest you replace only what's broken or worn, but replace that with component swhich won't break again as the original did. There are three small plastic gears in each of the stepper gearboxes which break/wear quite quickly under the strain of the mechanical work they are required to do. Replace those gears with quality hard-wearing steel/bronze ones (our specification). That's all. Oh, and while you're in there, for a few dollars add the small reinforcing ring to the air distribution drum to ensure it won't break in the future either. See the replacement gears inside a gearbox and our gear specifications.

 

Can I do this myself or will I have to pay a dealer or mechanic to do it?

-This is something that you will have to decide that for yourself. We (and others) can help if you are confident you have the basic skills, and many owners have. If you choose to have a specialist do the work, provide them with the replacement metal gears and instructions. To see what is involved, there is a video available on tape (eg from International Auto Parts) and a CD-ROM (from CarDisk). See our website's Alfa 164 Links for more details on where to find information on the Web about this.

 

What is an AlfaPro.com replacement gear set?

-A full set to rebuild both the stepper motor gearboxes consists of six gears. They replace the gears inside both gearboxes which are originally made of plastic (nylon). We also sell half-sets (ie. three gears) to rebuild just one stepper gearbox. Both gearboxes are internally identical and replacement gears fit either one perfectly.

 

What are the AlfaPro.com replacement gears made of?

-We designed these replacement parts for a very long life. They are a combination of instrument-grade bronze, mild steel and hardened steel. They are manufactured by a specialist workshop to exacting quality standards; they are not mass-produced. (Note that we do not use aluminium as we consider it too soft for this application). Some might regard our specification as "over-engineered", but this is the only way to ensure that you will not have to pull the dash/facia out again to fix this problem.

 

Is it difficult to rebuild the gearboxes with the new gears?

-No, this is the easy part! The replacements are installed quickly and easily. About 10 minutes per gearbox and it's done.

 

Where can I obtain the AlfaPro.com replacement gears?

-Currently only from us. Be assured that many 164 owners have ordered from us with complete satisfaction (the Alfa Digest and 164 Discussion Forum are sources of feedback about us if you wish to inquire or search back issues. Also, we archive some of their content). Not a single order, payment or shipment has ever been lost!

 

Do other components cause the climate control system to break down?

-As we've said, mostly it's the mechanical failure of the small gearbox attached to the stepper motors. However, some owners have reported the breakage of other plastic components: a rod which opens and closes the hot/cold air mixing door, or the distribution drum which directs air around the cabin. Thirdly, and more rarely, a stepper motor failure, probably because a gearbox jammed long ago and the motor has been straining to move it. Fourthly, an electrical failure in the system, including the ECU or computer itself (worst case scenario).

 

How can I tell if I have a problem other than the stepper gears?

-If the console climate control lights don't change, etc then the ECU or electrial circuit connections must be checked. A smooth whirring noise inside the dash (facia) from the motors acting but still no air/temp change may mean a broken rod or drum (see above). Visual inspection will be required. One easy check is to open the bonnet (hood) and remove the plastic cover just in front of the windscreen (windshield). (Carefully! It's fragile). Locate the air conditioning condensor (small cylinder with a spy-glass on top). Behind that against the firewall (you'll need to use a light) is a cable attached to a plastic rod; this controls the hot/cold air mixing door. Check that this is not broken.

 

Most of the rest of the system is (unfortunately) out of sight on the cabin side of the firewall inside the dash (facia) and disassembly will be required to determine the cause of your problem.

 

For further information see the links on the Stepper Gears index page.