Stepper Motors a closer look

[The kid]

Todays electronics are so much more than when I was a kid. Everything now is electronic. Let's take the speedometer, tachometer, gas gauge, volts, etc. In modern tractors these little critters may exist behind that pretty instrument cluster facing. So what is a stepper motor? In a since, it's a vibrating switch clock. it rocks a tiny gear from side to side in a oval fashion to spin a nylon gear. That gear is geared to another reduction gear that has a shaft that a molded pointer is presses on. Voltage comes from your vehicles computer and pulses voltage to keep the gears running. So the gear is stepping side to side. Thus calling it a stepper motor.

Here's a few pictures. I recently had two fail on my 2005 GMC Sierra gauge cluster. Simple enough to fix, but why did it fail. Proof is in the pictures. There are two coils inside the small stepper motor on opposite sides. Voltage pulses back and forth creating electromagnetic fields thus stepping the gears in motion. The failure was simple but very hard to see with the naked eye. The copper wire wound coils are as thin or maybe thinner than a human hair. One of those coil failed and burnt open probably from a loose connection over time.

Checkout these pictures.

The first picture is of the coils. You cam see the one the left is the one that failed. The pointy ends are actually the solder points which would be on the outside bottom of the stepper motor. Each motor has four solder connections.

 

[PANHAPP]

Really nice pictures Kid.

 

[k0ua]

Thanks for a look inside.

 

[npalen]

What kind of devices are the steppers operating? Maybe that's obvious and I missed it? Interesting stuff. Thks for the pics.

 

[The kid]

Stepper motors are used in a variety of devices. The most common are your dashboard gauges. If you have one that is stuck or doesn't operate all the time it is probably failing. The tiny motors are inexpensive and rather simple to replace. It does however require some desoldering and soldering skills.

Four 7mm screws holds the cluster in the dash of my 05 GMC. There are many documented pages on the net explaining replacing these both in text/pics and videos.

Stepper motors are used in plotters, vinyl cutters, printers and many other devices. I found it interesting how simply made they where. -kid

 

[bmaverick]

That is a dual action solenoid stepper motor you have. It's an AFIC stepper. AFIC (Actuators For Instrument Clusters).
These things are micro sized and made on automation production lines.

Here are some other products like it ...
BLDC motor, brushless DC motors, three-phase motors, stepper motors - MMT
ACP&D Limited - Actuators for Instrumentation Clusters

 

[Zebrafive]

I replaced several in my daughter's Impala. I am not very skilled with soldering printed circuit boards. The new stepper motors were cheap from ebay and surprising they did work when I put it all back together. I figured worst it would be the same as I started. Then time to get a salvage yard cluster.

One tip I learned: Twist the needles until they stop. Record the position where the needle stops. Then twist the needle off the shaft. If you just try and pull the needle off the shaft, the shaft may pull out of the stepper motor, ruining it. When reassembling, twist all the shafts the same direction you did to remove the needle. Put the needle on about 1/4 turn back from where it stopped at removal and then twist to original stopping point.

 

[The kid]

While we're still on the subject of instrument cluster steppers. I'm not expert but did a bit of research before diving into the replacements the first time. If you have some masking tape, blue,green it doesn't matter. Take some scissors and cut some narrow one inch strips about an inch to an inch and a half long and maybe an 1/16" wide.

Keep the tape handy (roll). Take an ordinary table fork and put. Some tape at bend (outside) of the teeth and leave some teeth showing. As your stated. Roll the pointer all the way to the right with NO pressure when it hits the end stop.

Now take your small tape strips and line it up with the pointers. Make sure you do all the exact same way so placement is without error. Now take your taped dinner fork and pop off the pointer. The curved fork acts as a lever and make it very simple to pop the pointers off.

BTW, I checked my speedometer today with a GPS and the speed was dead on the money.

Using a pencil type of soldering iron. The tip needs tinned. In other words a coat of solder on it. I buy a small tin of stuff I roll the tip in and tins the tip perfectly. I also use the smallest gauge of solder I can find. Plus to remove the old solder I use a ribbon wick. It's real fine woven copper designed to when you place it on top of the solder you want removed. You place your tinned iron tip on the braided wick and it sucks all the solder off the connection.when I get a chance I'll put up a few pictures of the stuff I use. It. Makes removing. Something from a printed board very easy.