What a turn signal cancelling cam does and why you need one

A turn signal cancelling cam is a small mechanical part that sits inside your steering column and automatically shuts off your turn signal after you complete a turn. On a 1966 C10, the turn signal does not cancel on its own — you have to reach up and flip the lever back to the off position by hand every time. Installing a cancelling cam fixes this, so the signal cuts off the moment you straighten the wheel.

The cam is a shaped piece of plastic or metal that rides against a spring-loaded contact inside the column. As you turn the steering wheel, the cam rotates with it. When the wheel returns to center after the turn, the cam pushes the signal lever back to off automatically. It is a small upgrade that saves you from forgetting to turn off the signal and annoying drivers behind you.

This is a steering column job, so you will be working inside the column housing itself. The work is straightforward but requires patience and attention to how parts fit back together. Most owners complete this in one to two hours.

Key Takeaways

  • The cancelling cam mounts inside the steering column and works by pushing the turn signal lever back to center as the wheel straightens.
  • You will need to remove the steering wheel, horn pad, and the upper steering column cover to access the cam location.
  • The cam slides onto the steering shaft and is held in place by the turn signal lever assembly — no fasteners required.
  • Reassembly order matters: install the cam first, then the turn signal lever, then the column cover, then the horn pad and wheel.

Tools and parts you will need

Gather these items before you start. You will need a steering wheel puller (a three-jaw puller works best, or a two-jaw if that is what you have), a socket set with a 9/16-inch socket for the steering wheel nut, screwdrivers (both Phillips and flat-head), and a small flashlight to see inside the column.

For the part itself, you need a turn signal cancelling cam kit designed for a 1966 Chevrolet C10. These kits are sold by classic truck suppliers and typically include the cam, a new turn signal lever, and sometimes a spring or contact assembly. The kit usually costs between $25 and $50. Order by your truck's year and model to may support the shaft diameter matches.

You may also want a horn pad removal tool or a thin plastic pry tool to avoid scratching the pad when you remove it. A clean cloth and a small container are useful for keeping screws and small parts organized as you work.

Removing the steering wheel and column covers

Start by disconnecting the negative battery terminal to prevent accidental horn set up while you work. Then remove the horn pad by prying gently around its edges with a plastic tool or small screwdriver. The pad is usually held by clips or a single screw in the center. Once the pad is off, you will see the steering wheel nut underneath.

Use your socket set to remove the steering wheel nut (typically 9/16-inch on a 1966 C10). Keep this nut — you will reinstall it. Now position your steering wheel puller on the wheel with its three jaws gripping the wheel rim evenly. Tighten the center bolt slowly until the wheel slides off the shaft. Do not hammer or force it; the puller does the work.

With the wheel off, locate the screws holding the upper steering column cover (the plastic or metal shroud around the column). On a 1966 C10, there are usually two to four screws on the underside of the cover. Remove these screws and slide the cover down and off the column. You now have clear access to the turn signal lever and the shaft underneath.

Accessing and removing the old turn signal lever

Look at the turn signal lever on the left side of the column. It is connected to the shaft by a small screw or clip. On most 1966 models, a single screw holds the lever arm to a collar that rides on the shaft. Locate this screw (it is usually on the underside of the lever where it meets the column) and remove it with your screwdriver.

Once the screw is out, gently pull the lever straight out and away from the column. It will slide off the shaft. You may see a spring or contact assembly attached to the lever or sitting on the shaft — note how it is positioned before you remove it. Take a photo with your phone if it helps you remember the layout.

If the old cancelling cam is still on the shaft, slide it off now. If there is no cam (which is the case on most original 1966 C10s), the shaft will be bare. Either way, clean the shaft with a cloth to remove any dirt or corrosion before you install the new cam.

Installing the new cancelling cam and lever assembly

Slide the new cancelling cam onto the steering shaft. The cam has a flat side or a keyway that must align with a corresponding flat or key on the shaft — it will only fit one way. Push it up the shaft until it sits at the correct height. Most kits include a diagram showing where the cam should sit relative to the column housing; follow this closely.

Next, install the new turn signal lever assembly. The lever arm slides onto the shaft above the cam, and the screw hole in the lever collar must align with the mounting hole on the column housing. Position the lever so it points downward (off position) when the steering wheel is straight. Slide the lever onto the shaft and align the screw hole, then install the screw and tighten it firmly but not so hard that you crack the plastic collar.

Before you reassemble the column cover, test the cam by rotating the steering shaft by hand (the wheel is still off). Turn the shaft left and right and watch the lever. It should move with the shaft and then snap back to center as the shaft returns. If the lever does not return smoothly, the cam may not be seated correctly — remove the lever and check the cam position.

Reassembling the steering column

Once the cam and lever are working smoothly, slide the upper column cover back up over the shaft and align the screw holes. Install the screws and tighten them snugly. Do not overtighten; the cover is usually plastic and can crack.

Now reinstall the steering wheel. Align the wheel so the spokes are level (or in your preferred position) and slide it onto the shaft. Install the steering wheel nut and tighten it to a firm fit — typically 30 to 40 foot-pounds of torque, though a 1966 C10 is not critical about this. If you do not have a torque wrench, tighten until the wheel is snug and does not move when you try to wiggle it.

Reinstall the horn pad by pressing it back into place until the clips or screw engage. Reconnect the negative battery terminal. Now start the truck and test the turn signals. Turn the wheel left and right and listen for the signal to click off as the wheel returns to center. The lever should move smoothly and the signal should cancel reliably.

Troubleshooting common issues after installation

If the turn signal does not cancel, the cam may not be seated fully on the shaft or the lever may not be positioned correctly. Remove the column cover again and check that the cam is pushed all the way up the shaft and that the lever is aligned with the cam. The lever contact point must touch the cam as the wheel returns to center.

If the lever feels stiff or does not return smoothly, the cam or lever may be binding against the column housing. This usually means the cam is sitting too high or the lever is not aligned properly. Loosen the lever screw, reposition it slightly, and test again. Sometimes a small adjustment of 1/8 inch makes the difference.

If the signal cancels too early (before the wheel is fully straight), the cam may be positioned too far down the shaft. If it cancels too late, the cam is too far up. Most kits include a spacer or shim to adjust this — check your kit instructions for the correct position.

Frequently Asked Questions

Can I install a cancelling cam on a C10 that already has one?

Yes. If the old cam is worn or the signal does not cancel reliably, remove the old cam and lever assembly and install a new kit. The process is the same. Make sure the new kit is designed for your year and model so the shaft diameter matches.

Do I have to remove the steering wheel to install the cam?

Yes. The wheel must come off to access the column cover and the shaft. You cannot reach the cam location with the wheel in place. The wheel puller is the safest way to remove it without damaging the shaft or wheel.

What if my steering column has a different layout than the one in the instructions?

1966 C10s can vary slightly depending on whether the truck has a manual or automatic transmission and whether it has a tilt column. Check the kit instructions for your specific configuration. If your column looks different, contact the supplier before you start — they can confirm the kit will fit your truck.

Will the cancelling cam affect my horn or other steering column functions?

No. The cam sits on the shaft and does not interfere with the horn pad, horn contact, or any other column function. It only affects the turn signal lever position.

How long does the cancelling cam last?

A quality cam should last the life of the truck. The cam is plastic or metal and does not wear out under normal use. If it fails, it is usually because the lever contact point has worn smooth, which means the whole assembly needs replacement — not a common problem.