Disabling the Miata NC Steering Wheel Lock
Because I tow, as well as daily drive, my Miata NC-2 PRHT , I wanted to be able to disable the steering wheel lock so that the Miata would follow the RV through turns.
Towing a Miata is easily done by putting the ignition switch in the Acc. position, but then the power to all of the accessories is ON and some NC Miata towers have reported the Miata's battery going dead while being towed.
I elected to permanently disable the steering wheel lock. Below are the steps I took to achieve that task.
All components of the steering wheel lock mechanism are mounted below the steering column tube and are bolted to a saddle that is welded to the top of the tube.
The steering wheel lock itself is a spring loaded metal "lug" that is in a raised position when the ignition is LOCKED and is mechanically lowered when the igniton is in any other position.
The lowering action is performed by a "follower" that is in a cam slot in the outer barrel of the lock mechanism.
After removing the plastic shroud between the back of the steering wheel and the instrument panel, you will see two domed-top bolts on top of the mounting saddle.
are button head "shear head" bolts, not rivets . They are
made with a head that is designed to break off at a specific torque
when installed. They are normally not removable.
They are regularly used on ignition switches so that thieves cannot just unbolt the switch, unlock the steering wheel, and take off with your car.
These bolts MUST be removed in order to drop the switch from the steering column.
Using a VERY sharp pointed chisel, I gave each bolt a couple of heavy whacks in the counter-clockwise direction as with any other right hand thread bolt. One whack is to seat the chisel point into the right side of the bolt head and another whack to break torque. Once the torque is broken, the bolts will unscrew with the fingers.
|Here is a picture of the 2 removed shear head bolts (on the left) and the 8 mm stainless button head Allen bolts and lock washers that I used to replace them (on the right) .|
|Here are pictures of the steering wheel locking lug in the raised position (left) and in the lowered position (right).|
|Here is a picture of the slot in the steering column into which the locking lug fits. The large rectangular hole is in the outer steering column sleeve. The inner round-end hole is in the tubular steering shaft.|
|I used a .5 inch wide strip of .030" shim stock to cover the locking lug. When the lock is reclamped to the steering column, this shim strip will prevent the locking lug from extending up into the hole in the tubular steering shaft and locking the steering wheel.|
|Here is a picture of the ignition switch assembly rebolted to the steering column. You can see the end of the brass shim strip protruding from the mating joint.|
That's all there is to it folks. It works fine.