DIY: How To Replace The Turn Signal Switch on a Classic Air-Cooled Porsche 911
A common failure point in the Porsche 911 lighting system is the dash headlight switch itself. Find out how to replace it with this short DIY.
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A very common issue with the air-cooled Porsche 911 is that the turn signal switch, which also controls the high beams, eventually starts to malfunction. The switch contacts that control the high beam function begin to stick and you end up with high beams that always stay on, never come on, or come on/off when you use the turn signals. The best solution is to replace the turn signal switch assembly with a new one. It may appear like a daunting task but when you break it down step-by-step it is very straight-forward.
Model Years Applicable:
All Porsche 911 cars 1976 to 1989. Earlier cars use different switch units but follow a similar installation. The procedure shown here is on a US-spec 1983 911SC.
Tools Needed:
- Small flat screwdriver
- Flashlight
- Needle nose pliers
- Circlip pliers
- Plastic trim removal tool
- 27mm deep socket
- Impact wrench or breaker bar
- 1/2” ratchet
- Penetrating oil
- Side cutting pliers
- Electrical contact cleaner
- Small zip ties
Parts Needed:
Installation Procedure:
Step 1: Disconnect Battery
Disconnect the negative battery terminal.
Step 2: Remove Steering Wheel
If you have a stock steering wheel, remove the horn pad first. On 1974 and later cars the horn pad just pulls off the steering wheel. On earlier cars you rotate the horn pad counter clockwise to release it. If you have an aftermarket wheel with a small horn button (like a Momo or a Nardi), use a plastic trim tool to pry the horn button off.
In either case, once you have the horn pad or button off, you will see some horn wiring and the large steering wheel nut down through the center. Disconnect the horn wiring and set the horn pad or button aside.
You will need to remove this large nut to get the steering wheel off. If the steering wheel has never been off, you may have difficulty with this. Spray a little penetrating oil on the threads of the nut and let it soak in.
You may need a helper to hold the wheel static while you loosen the nut counterclockwise with a ratchet, breaker bar, or impact wrench. Do not lock the steering wheel all the way to the end of the steering rack’s travel to keep the wheel static while you loosen the nut. This could damage your steering rack.
After you loosen the nut, remove it and the large wavy washer below it and set them aside. Note the orientation of the wheel in relation to the steering column so you can put it back in the same way. An easy way to do this is to mark a pair of dots on the splined shaft and the bottom of the wheel hub with a sharpie. Pull the wheel off the steering column splines.
Step 3: Remove Steering Column Clam Shells
Remove the small screw on each side of the steering column at the seam between the two clamshells.
Remove the two screws below the column splined shaft to remove the lower clamshell.
Take note of this ground wire connected under a screw so you can put it back in the same location during reassembly. On the 911SC it is on the lower right.
Next remove the 2 screws above the splined shaft to remove the horn contact pad
Below the contact pad you will see two more small screws. If you remove those the upper clamshell will come off.
Its a good idea to label the clamshells so you can install them back the same way they originally were.
Step 4: Remove Old Turn Signal Switch
Before removing the old turn signal switch, study the way the harness is laid out on the new one. It is composed of 2 main branches, one with a round plug, another with separate spade connections, and a ground wire. If your old turn signal switch wiring has not been modified, the connectors and wire colors on the new switch should be the same.
On the old turn signal switch still on the car, notice the electrical contacts on the left side, just behind the turn signal stalk. If you operate the stalk up/down and forward/backward you can see the contacts move. Compare how the old contacts and new contacts move on each switch and you will see the difference.
Now remove the 2 screws on the left side, holding the turn signal switch body to the steering column mounting brackets. Cut any small zip ties holding the switch body to the column.
You should now be able to maneuver the turn signal switch assembly off the column and let it hang by its harness.
Step 5: Remove Headlight Switch
Next you will need to free the headlight switch from the mounting hole in the dash so we can let it hang and have better access for all the turn signal wiring that needs to be reconnected. Follow steps 2 to 3 of this procedure to do this.
Note: If you have not serviced your headlight switch before, this is a good time to inspect and repair any faulty connections per step 4 of the procedure linked above. If your headlight switch is burnt or damaged, consider replacing it with a new one while it is accessible.
Step 6: Disconnect Old Switch and Reconnect New Switch
Since there are quite a few connections on the turn signal switch, the easiest way to connect the new one is to swap out each connection on the old switch with the new one. Follow the old turn signal switch harness and note where it runs along the steering column and through an opening in the dash. There is just enough room through that same route to push the new switch harness in alongside the old one. We will swap out each old switch connection with the new switch connection one by one and then pull out the old disconnected harness.
Pull off the horn contact on the brown and white wire at the top of the column and save it for later.
Follow the old switch harness to a round black plug under the driver side of the dash. Make sure you have the correct plug as there are several that look the same.
Disconnect the turn signal switch plug from under the dash.
On that same harness branch as the plug is a white rectangular plug on a black and white wire that also needs to be disconnected. Do not disconnect the similar plug on a yellow wire.
At this point that branch is completely free and can be pulled out from under the dash. That should give you enough space to insert both branches of the new harness in the same opening. Reconnect the round black plug and the white rectangular plug in the same locations as the old ones.
Now you are ready to reconnect the second branch which has four individual spade connectors that go on the back of the headlight switch. Swap out each old one and replace it with a new one of the same wire color, cleaning the connections as you go.
The last connection on that branch is another rectangular white connector on a gray wire. Reconnect that one and pull out the old switch harness completely. Use a few zip ties to tuck the new turn signal harness wiring up under the dash out of view.
Step 7: Test New Turn Signal Switch
Secure the new turn signal switch body back on the steering column mounting brackets with the same two screws as before. Reconnect the old horn contact on the brown and white wire of the new harness.
Leave the headlight switch and the ground wire and the horn contact hanging so they do not touch anything.
Temporarily reconnect the negative battery cable and turn the key to the “on” position but do not crank the starter. Hold the headlight switch body with one hand and pull the center shaft out to turn on the lights. Test both turn signals by pulling the stalk up or down and the high beam function by pulling the stalk towards or away from you. The turn signals and high beam functions should be completely isolated from each other now.
If everything checks out OK, turn the key to the “off” position and disconnect the negative battery cable once more for final reassembly.
Step 8: Reassemble Steering Column Parts
Replace the headlight switch back into the dash per step 7 of this procedure.
The remaining steps are the reverse of steps 3 and 4 above. Reinstall the upper clamshell with the two screws above the steering column and with the horn contact wire positioned through the center opening as shown.
Tuck the horn contact wire under the clamshell and reinstall the horn contact pad with its two screws.
Reinstall the lower clamshell with its two screws making sure to connect the ground wire back into its original location under the clamshell.
Reinstall the screws on each side of the clamshell.
Step 9: Reinstall Steering Wheel
Place the steering wheel back on the splined shaft in the same orientation as when you first removed it. Place the large wavy washer and hex nut on and torque to 50 Nm (36 ft-lbs). You may need a helper again to hold the wheel static while you torque the nut clockwise.
Reconnect the horn wiring and secure the horn button or horn pad back on the steering wheel. Reconnect the negative terminal back on the battery and you are done.
Your turn signal switch is now ready to go. You should have turn signals and high beams that behave as they should for many years to come.