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Ampera Advocate
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Discussion Starter #1
Can someone please assist by telling me if there are any instructions to replace the steering lock available? My search on the forum was not successful. Thanks
 

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Hi Graham,

There are some threads somewhere but I remember mine quite well.

The dash undertray comes off pretty easily with three or four screws (torq?) holding it.

You need to somehow remove the two shear bolt heads to allow the old steering lock to slide off (can't remember if its up or down). Will describe further below.

First problem noted after the bolts were removed was that the steering lock has to be unlocked to remove it. When enabled it isn't allowed to slide. I just powered the car up when the bolts were off to remove it and then powered down to unplug it.

To re-install I just plugged it in, slipped it into position and fitted two new normal socket cap screws (6mm I think).
If it is in the locked position when new and can't be fitted, power the car up with it plugged in and then power it down again ignoring the error message that it is locked when it should be unlocked. It soon sorts itself out.


Job done, now how to remove the bolts.

I first tried gripping the domed ends of the bolts but they didn't budge.
Others have successfully sawn a slot accross the head and used a flat screwdriver to remove them.

I have a 4" grinder and after speading a large cloth around the footwell, proceeded to grind the heads off the bolts like a "bull at a gate"!
It is a bit messy and not a little scary but doesn't take long.
Biggest problem is that the bolt thread tapers out slightly to the head so you have to undercut the head area of the old lock casting.

I then used a couple of strong flat screwdrivers to lever the body of the lock to slide it (Up?) after first powering the car up to unlock it.

Once it slides an inch or so it will drop off and you will wonder what all the fuss was about.

Let me know if you are struggling as I will be around over the weekend and have amassed a lifetimes stock of tools and a very big hammer to fall back on. :cool:
 

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I got a replacement lock but haven't fitted it yet. To be honest, I get the error maybe 2 times a year, and I've not been stranded, touch wood. I think Handyandy said he still gets the error, even with the new unit - that has put me off and has made it a lower priority for me.
 

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Regarding this issue I'm wondering if its possible, or if anybody has tried, to just disable it altogether. I appreciate the car probably throws a wobbly and wont start if it were simply unplugged but could it possible to have it plugged in but physically remove the locking pin so its never actually engaging on anything? This way the little motor will have virtually no load on it and won't burn out as easy which from my understanding is the problem?
Once upon a time I had a '92 Fiat Panda which whilst mostly electronics free had a fuel cut off solenoid in the carb to prevent overrun when you turned the car off, with age these would stick on causing a no start, the easiest solution was to just cut the end off it, I wonder if a similar thing could be achieved here...
 

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I believe someone here may have removed the old unit, and replaced it with one that's simply cable-tied out of the way so it can't do any harm!

Removing the locking pin in a way that lets the motor spin endlessly can be done, but it might have an undesirable side effect. This is entirely my speculation, but GM may be detecting the stalling of the motor, with it's huge current surge, as a way to know that the pin has moved. Measuring the time intervals between the open & closed surges may be their way of detecting that the pin has/has not moved at all. If I were making a super-cheap-and-nasty unit, this is how I'd do it. A current measuring IC is a few cents, if they even use that - maybe they simply pass the motor current through a low-ohm resistor & measure the voltage drop using a small cpu, this would be virtually free to implement, and would save a few cents on proper limit switches or hall-effect sensors. Judging by the way they skimped on both the boot clips, and the door switches, I would not put this degree of penny-pinching past them, sadly. Which is why I've ended up making replacements for both those items. And why I always park with wheels perfectly straight ahead, always.
 

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Discussion Starter #7
I've now had the replacement fitted because mine had recently locked up totally. I was also getting the message to carry out the steering lock service every time I started the car. Not seen the message since so fingers crossed.
 

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I always park with wheels perfectly straight ahead, always.
Can you explain the reason why it is beneficial to park with wheels straight?

According to the manual the process to enable the steering wheel lock is the same as the process to disable the steering wheel lock 🤷‍♂️
 

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Can you explain the reason why it is beneficial to park with wheels straight? ...
I assume the pin the juts out from the lock and fits into a similar-shaped recess in the steering wheel shaft. I can't remember if the pin is spring-loaded, I have a suspicion it is, so if the steering wheel is at say 30 degrees off centre, then the pin won't slot in; but anyone trying to steal the car & turn the wheel would hear it click in and lock hard at the central position, also at the extreme end positions, if there's a slot there as well.

When it come to unlocking & withdrawing the pin, let's assume that the steering wheel is ever-so-slightly off centre; in that case, I'd expect some side-force or friction between the pin & the slot. The rather small motor will surely have to provide a greater force to withdraw the pin, than it would have if the wheel is perfectly aligned and there's a bit of slack on each side of the pin. Having to create more force means the motor runs slower, takes more current, does more work & generates more heat. I've noticed the steering wheel twitch a bit on occasions; I think GM might give it a shake as the unlocking happens, in order to make sure the friction gets removed momentarily & to help the pin retract. But I don't notice this shake every time, I might start holding the wheel gently as I start & see if it always happens, or not.

The same applies when locking, but it's potentially much worse I think. If the wheel is at 30 degs so the slots don't line up, the motor has to compress the spring behind the locking pin, so the pin can snap into place later if wheel is turned. The work done by the motor in this case is far greater than it would be, had the slots lined up and there was no load to speak of. So, I think the motor is badly overloaded. Here's a pic of the armature out of my first lock. This hadn't failed, but I was getting a fair few warning messages to decided to get it changed anyway. I also wanted to have a look inside it !

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When I was young I did a lot of slot-car racing. (Scalextric 1/32 scale, but done properly at clubs, wood/hardboard tracks lovingly modelled etc. There was a great, huge, track, about 6 lanes, at Hammersmith I went to on occasion). I used to wind my own armatures, trying to get max power from the motors available; some were worse quality than this GM one, some were far better. We used to get the armatures dynamically balanced so some of these would run at close on 200,000 rpm on 12V at zero load. I can guarantee the commutator in this motor will explode at a lot less than that! The wire we used was usually far thicker than what's on this armature; this looks like 34 SWG or thereabouts. We used to go down to 24 SWG on the extreme high-performance motors, these would draw maybe 10-15A at 12V when stalled! We'd have one car-battery per lane (slot-car) as sharing one battery between 2+ cars you could feel the loss of power when other guys accelerated. Despite being Scalextric scale, and the motors physically the same size as this one here, these slot cars were serious bits of small-scale engineering.

During all that time, I never, ever, got to see an armature showing the signs of extreme heat that this picture shows! And I saw a lot of armatures. I rest my case, M'lud. :)
 
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For comparison, here's the armature from a Miura Group 20 motor, circa 1972. While not the ultimate armature of the day, it was pretty darn close, and was the motor used for a standardised class of racing with a standard chassis, rather like Formula Ford, the idea being to compare driving skills rather than who could make the fastest car (usually the one wih most money, a commodity in short supply even then!).

As you can see, the wire used is considerably thicker, I'd say probably 27 or 28 SWG on this one, the holes are the dynamic balancing, different ones & sizes in different places, and the wire connections to the commutator have been bound up with strong twine & araldited to prevent explosions at high rpm. This armarture has seen a lot of racing, and yet there's no sign of overheating, despite these things running hot enough for the motor casing to burn your skin immediately after a race.
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