What a turn signal cancelling cam does and why yours might need replacing

A turn signal cancelling cam is a small rotating part on the steering column that automatically shuts off your turn signal after you complete a turn. On a 1966 Chevrolet C10, this cam sits inside the steering column housing and works by pushing a lever that breaks the electrical circuit to the signal lights once the steering wheel returns to center.

When the cam wears out or breaks, your turn signals stay on after you finish turning, or they don't come on at all. You end up cancelling them manually by hand, which defeats the safety purpose of having an automatic shutoff. A worn cam can also cause the signal stalk to feel loose or sloppy when you move it, or the lights may flicker unpredictably.

Replacing it is a straightforward job that takes about an hour and requires only basic hand tools. You do not need to remove the entire steering column—just the horn pad and the upper column cover.

Key Takeaways

  • The cancelling cam sits inside the steering column and automatically turns off your turn signals when you straighten the wheel after a turn.
  • A failed cam leaves your signals on permanently or prevents them from working, forcing you to cancel them by hand.
  • Replacement requires removing the horn pad and column cover, then unbolting the old cam and sliding in the new one—no steering wheel removal necessary.
  • A 1966 C10 cancelling cam costs between $15 and $40 depending on whether you buy OEM or aftermarket, and the job takes about one hour.
  • If the cam is stuck or the steering column feels damaged, have a mechanic inspect the column before you attempt the repair.

Tools and parts you will need

Gather these items before you start. You will need a socket set (1/4-inch and 3/8-inch drives), a screwdriver set with both Phillips and flat-head tips, a small flashlight or headlamp, and a container to hold small fasteners so nothing gets lost inside the column.

For the part itself, order a turn signal cancelling cam assembly designed for a 1966 Chevrolet C10. Verify the part number with your supplier—common replacements include Chevrolet part number 1955476 or equivalent aftermarket versions. Some suppliers sell just the cam; others sell the entire cancelling cam assembly with the spring and lever. Either works, but the full assembly is more reliable if the spring is also worn.

You do not need a steering wheel puller or column removal kit. The cam sits above the steering wheel and is accessible once the horn pad comes off.

Removing the horn pad and column cover

Start with the engine off and the steering wheel straight ahead. Look at the center of the steering wheel—you will see the horn pad, which is usually a round or oval plastic or metal cover with the Chevrolet bowtie emblem. On a 1966 C10, this pad is typically held by two or three screws from the back side, accessible from underneath the wheel.

Reach under the steering wheel and locate these screws. Remove them with a Phillips screwdriver and carefully pull the horn pad toward you. Be gentle—the horn wire is still attached. Once the pad is loose, disconnect the horn wire by pulling the spade connector straight off the terminal. Set the horn pad aside in a safe place.

Now look at the steering column directly above the steering wheel. You will see a plastic or metal cover that wraps around the column. This is the upper column cover. It is held by two or three small bolts or screws. Remove these fasteners with your socket set or screwdriver. The cover will slide up and off the column, exposing the cancelling cam assembly underneath.

Unbolting and removing the old cancelling cam

With the column cover off, shine your flashlight into the opening. You will see the cancelling cam—a small round or oval part with a spring attached. The cam is bolted to a bracket that sits on top of the steering column. Locate the bolt or bolts holding it in place; on most 1966 C10 models, there are two bolts.

Use your socket set to remove these bolts. Keep them in your fastener container. Once the bolts are out, gently lift the old cam assembly straight up and away from the column. The spring may still be attached; if it is, note how it sits so you can reinstall it the same way on the new cam.

If the spring is separate, remove it now and set it aside. Inspect the spring for cracks or permanent bending. If it looks damaged, replace it along with the cam. If you bought a full assembly, the new spring will be included.

Installing the new cancelling cam

Take the new cancelling cam assembly and position it directly above the steering column in the same location where the old one sat. The cam should align with the bolt holes in the bracket. If your new cam came with a spring already attached, verify that the spring is oriented the same way the old one was—the spring should push the lever that touches the turn signal stalk.

Insert the two bolts through the bracket and into the column. Hand-tighten them first to make sure the cam sits evenly. Then use your socket set to tighten them firmly, but do not overtighten—these are small fasteners and can strip easily. Snug is enough; you are not torquing down a wheel lug.

Once the cam is bolted down, rotate the steering wheel slowly left and right through a full range of motion. The cam should rotate smoothly with the column, and you should feel the lever engage and disengage as the wheel turns. If the cam binds or feels rough, stop and check that the bolts are not too tight or that the cam is not misaligned.

Reinstalling the column cover and horn pad

Slide the upper column cover back down over the steering column and align the bolt holes. Insert the bolts and tighten them snugly with your socket set. The cover should sit flush against the column with no gaps.

Reconnect the horn wire to the horn pad by pushing the spade connector back onto the terminal until it clicks. Position the horn pad back on the steering wheel and insert the screws from underneath. Tighten them evenly so the pad sits centered and does not rock.

Turn the ignition on without starting the engine. set up the turn signal stalk to the left and hold it. The left turn signals should come on. Release the stalk and turn the steering wheel left—the signals should shut off automatically as the wheel returns to center. Repeat this test on the right side. If both sides work, the installation is complete.

Testing the turn signals and troubleshooting

Before you drive the truck, test the turn signals in all directions. Turn left, turn right, and make a U-turn. The signals should cancel automatically each time the steering wheel returns to center. If they do not cancel, the new cam may not be seated properly, or the spring may be installed backward.

If the signals still do not work after installation, check that the wiring harness under the column cover is still connected. A wire may have been accidentally pulled loose when you removed the cover. Trace the wires from the turn signal stalk down into the column and verify they are all plugged in.

If the cam feels stuck or the steering wheel is hard to turn after installation, stop when ready. This usually means the cam is misaligned or the bolts are too tight. Loosen the bolts slightly and check the alignment. If the problem persists, the steering column itself may be bent, and you should have a mechanic inspect it before driving.

Frequently Asked Questions

Can I drive the truck if the cancelling cam is broken?

Yes, but you will have to cancel the turn signals manually by hand every time. This is unsafe because it takes your attention off the road and increases the risk of forgetting to turn them off, which confuses other drivers. Replace the cam before regular driving.

What if the new cam does not fit the bolt holes?

Verify you ordered the correct part for a 1966 C10. Some Chevrolet trucks from adjacent years have slightly different column designs. If the holes do not align, contact your supplier and confirm the part number. Do not force the cam into place.

Do I have to remove the steering wheel to replace the cancelling cam?

No. The cam sits above the wheel and is accessible once the horn pad and column cover come off. Removing the wheel would add an extra hour and require a steering wheel puller, which is unnecessary for this job.

How long does a cancelling cam usually last?

Most cams last the life of the truck if they are not damaged by impact or corrosion. A 1966 C10 that has been driven regularly for decades may wear one out straightforward from millions of cycles, but this is not common. If yours failed, it was likely damaged or exposed to moisture inside the column.

What if the turn signal stalk feels loose after I install the new cam?

A loose stalk usually means the cam is not seated fully or the bolts are not tight enough. Remove the column cover again, check that the cam is pushed all the way down onto the bracket, and tighten the bolts a bit more. The stalk should feel firm when you move it.